Need ideas to stop porpoising?
 

Got the new Honda 225 installed and have 10 hours on it on my 1989 Seacraft 23WA. When there is a little roll on the water the boat tends to want to porpoise. I had moved 20 # lead up front in the anchor hole in the bow, after yesterday still doing the same, added another 40# lead. May get out again Tue or Wed. The 225 has awsome power, but you do know you have the extra 220+# on the back compared to the 200 hp Merc. I have about 6 hours on the current fuel, so will fill it up again when I go out to get an idea of fuel burn for the 6 hours running. I am running a 15 hp Honda off the main tank, but that thing does not use a lot of gas just trolling.
I am not getting any water through the scuppers, sure need to watch the big wakes from the stern, if you can't get turned in time. I do get a little water into the engine well with the wakes, but they drain right out. I had to pull the hatch and reseal it good as the engine installer had to replace the old one because of the orginal engine bolts and did a lousy job sealing it.

Re: Need ideas to stop porpoising?
 

Is the motor trimmed all the way down, and is it mounted at the right height? Too low will cause some strange things. If you mounted it at the same height/hole as the 200, you have a couple of hundred extra pounds on the back now.

Trim tabs? do you have them?

Move the batteries forward?

If all else fails, bracket?

You might want to check the transom for wetness, if it's soaked, it will add a bunch of weight back there too.

Re: Need ideas to stop porpoising?
 

Yes, I have trim tabs, but hate to use them as the do slow you down 2-3 mph. The transon is bone dry as the boat is stored inside anytime it is not in use. I hope the xtra weight in the bow will help and I will just have to learn the new handling characteristics and make adjustments.
The engine is mounted in the same holes and height as the old one, position looks good. It does put out quite a boil when slowly accelerating. 14.25 X 17 SS prop gives me around 30mph @4000rpm.

Re: Need ideas to stop porpoising?
 

doel fins or permatrim. Try removing the 15hp just as an experiment (that's another 120 pounds). If you're not getting enough negative trim . . . then you can always install wedges.

How's the speed compared to the old 2.4L 200hp merc?

Re: Need ideas to stop porpoising?
 

All of these responses here are valid but unfortunately none of the offered solutions will cure every porpoising problem. And yet every one of them will resolve many such problems. Changes along with your observation will help. You mentioned your 225 is 220lbs more than previous motor - that is significant. Did you have a fin on the old motor? I could definitely see a benefit to such in the windy chop of the Sound. Consider four holes in your new motor. A hydrofoil like a Doel-fin or Stingray or SE Sport 300 will help you plane faster with out drag, but at 30 mph trim tabs will not be the efficiency burden you might think and when properly trimmed they will help dramatically in a heavier 23' that maybe overweighted astern.

Weight definitely needs to be re-distributed. Remove the kicker as Bigshrimpin suggested - that is far more significant than adding 60lbs of lead in the bow - and remember the kicker sits back a foot behind the transom. Remember the teeter-totter back in school -- slide farther out from pivot point and you could outweigh the bigger guy, granted not a problem now, Big Fella ;). Besides who needs a kicker with that gas-sippin Honda. Is your idle too fast for Salmon?
If you use a bait tank try running with different amounts of water in it, 30gal is about 240lbs, might need to move it fore or aft.

I've never seen a 23WA but it does sound like the rear end needs to get out of the water a bit. Maybe a stern-lifting prop is helpful. If you are avoiding the trim tabs only for efficiency loss, experiment with them a bit. First make sure they are not set all the way up, if so, I'd wager that's half of the problem. Take a straight edge and set them parallel,or inline with the hull. At the very least it will make the boat believe it's a foot longer. Boat racers in Miami used this trick in the old days. Just an extra foot of stainless plate flush with the hull...It ain't rocket science - just hydrodynamics...whatever...

If you had bad seal on the mounting bolts (assuming they went through the transom) You might get a moisture meter on the transom. Salt water attracts moisture and I know its wet up there most of the year so even though you store in shelter, if it gets wet it stays wet awhile... Sorry to ramble. Good Luck

Re: Need ideas to stop porpoising?
 

If you're going to try a stern lifting prop I'd recommend a Rev 4.

Re: Need ideas to stop porpoising?
 

A lot of good ideas here, IMHO, it's a balance issue. I haven't heard of anyone having this type of problem with a WA/Cuddy, usually just the CC's. I would try removing the kicker, and see if it get's better, if it does, than it's a balance problem. I don't remember where the gas tank is mounted in a WA, but if it's mounted too far back, and is full, that is something you might want to look at. I know when my in-transom livewell is full, 44 gals, it really screws up the balance. These boats were designed very well, and IMHO, anything past 450 pounds of motor on the back really gets them out of balance.

Re: Need ideas to stop porpoising?
 

My boat was not prone to porpoising until a repower increased motor weight by ~130 lbs and moved it 2.5' aft on a bracket. I would never consider a bracket if you're already having a problem with the motor hanging on the transom!

Besides a fundamental rebalance, like removing the kicker and moving batteries and baitwells, I'd try a Doelfin or equivalent first, as that and engine trim are probably the strongest medicine. A stern lifting 4B prop will also help. I tried a Mirage Plus 3 blade and a 4 blade Michigan Apollo; the latter was much better. On my digital trim gage (where 0% is all the way down, and 100% is full up, just before tilt kicks in), the Mirage would porpoise at any trim setting higher than 50%; the Apollo won't porpoise till you get up around 70%! All of this testing was with Doelfin installed, as that was the first thing I tried. It seems to amplify the effect of engine trim and will also drop your min planning speed.

Re: Need ideas to stop porpoising?
 

Could be just your prop design. An omc viper "bow lifter" makes mine porpoise with anything above minimal trim. My michigan apollo won't porpoise until about 50% trim. Looks like the rev 4 is gonna be the "perfect SeaCraft prop".

Re: Need ideas to stop porpoising?
 

I ran 22" stilleto props on my 23 cc with twin 115's on a bracket. I moved up to 24" props and although they were the same brand and model, the bow now runs amazingly flat. I would fool around with another 17" prop. That is a very popular model so finding a buddy to lend you his shouldn't be a problem.

Filling your boat with lead or using a doelfin while useful is merely a bandaid for your problem. You may have broken a baffle in your fuel tank. Try swapping props and get back to us.

Re: Need ideas to stop porpoising?
 

Bushwacker borrowed my mirage + and plotted a performance chart. I expected to lose in hole shot, min speed to plane, midrange, mpg, and handling. The 4 blade also beat the Mirage + top end! This was deflating. Contrary to my p brained belief. More drag = higher top end?

My `89 20 sf {c.c.} is running a `96 ocean pro 150 @ 365#s. I had a Mich rapture 14 1/2 x 17 BOW lifting prop. On the hole shot my bow would rise to the point of almost losing sight of the ocean b4 planing off while standing. My cav/vent plate was also 3/4" below the keel which would tend to pull down the stern as well.

The mirage changed the whole dynamics of the boat, and that was b4 I moved the motor up 1 hole. It used to slap the chop, now I slice it. The angle of attack is MUCH more acute. The hole shot lifts the stern and the bow shoots forward ,not up! I dont use nearly as much negative trim to keep her down while running , and I picked up a couple mph top end. Lost a little grip trimming up and would blow out sooner.Moved the motor up and got some rpm and more top end. 3 mph total 2 way gps. No tabs or Bimini on....yet.

Re: Need ideas to stop porpoising?
 

Thanks for all the replys. Lots of information to think about. YES, I did have a stingray fin on the merc 200. I had thought about installing it but it does not look like a good fit to the honda. I saw on WestMarine site that they have a new type fin that installs w/o drilling but is 249.00. I ABSOLUTLY cannot go w/o my 15 Honda for a trolling for salmon fishing.
I had thought about the batteries, but that would take major work to do that, definately a good idea though.
I haven't tried top speed yet but I think it is going to be in the mid 40's as I got 44mph w/the 200 Merc. I only have 10 hrs on it now and I did run it up to 5K and was sitting at about 42mph. The last 3 trips have all been in 2-3ft chop so speed was not an issue there.
I like the idea w/the trim tabs, I will have to try it next time out. I was wanting to get out a couple more times this week but plans changed dramaticaly this morning, spent all day at the hospital w/wife and her 98 YOA mother and things are not looking good there, so I know where my time will be for a while now.
I will get back on the water ASAP.

Re: Need ideas to stop porpoising?
 

Lots of good advice. I hear you about not wanting to remove the kicker. Having that extra insurance on your boat is nice . I think Briguy is right on with his advice by trying the prop first then if that don't work put on the doel-fin. Those would be the two easiest things to try first before going to the extreme of moving fuel tanks batteries etc.. Bushwacker is right on about the bracket. Sorry to hear about your mother in law. At lease you have a salmon season :(

strick

Re: Need ideas to stop porpoising?
 

Raise the motor, I will bet its too low which drags the Cav plate, do that first. Never heard of a WA with this problem but thats alot of weight if everything is still back there I guess.

Re: Need ideas to stop porpoising?
 

Hi Gary;

Been reading all the good info which is all very valid but you are avoiding using the TABS which is the answer to your problem. All boats designed and made from the factory are tested with light loads and no extra weight. As time goes on we add and change all kind of things. Shift weight and adding stuff like kickers and 220 Lbs. for today’s newest 4 stroke motors, large live wells and what ever else we think is cool. Gary you need to look at Tabs like pilots look at flaps on a plane you just need to use them to control your boat the way you want it to run.



Fellow-Ship


Just for the Grins :D

Re: Need ideas to stop porpoising?
 

Hey G, do you have a long shaft on your new motor if so this can cause some porpoising if its not the right height in relation to your transom....

Re: Need ideas to stop porpoising?
 

I was out again yesterday and it was a fairly calm day, had two of my late-teen grandsons w/me and I had moved a total of 60#'s of lead to the front of the boat. To my surprise, the porposing has just about (90+%) gone away. The first few trip we had a lot of chop and rolling water and that may have had more to do with it than anything. I did lower the trim tabs slightly, don't know if the were even or not had not set them prior to going out. As soon as things calm down around here and I have time I will dig more until the problem is solved.
I know I had a friend who had a Wellcraft w/225 Suzuki on a bracket and he had really had a lot of porposing on his boat. He has since sold it so I doubt if he ever solved the problem there.

Re: Need ideas to stop porpoising?
 

Can u post a pic of the cav plate in ref to the transom ? take a side shot. .5 to 1.5 above the pad. look and see if there is a tiller pin in the transom bracket make sure it is in the bottom hole Iam not a Honda Mech but Iam a Merc and you can run the mercs withit out giving u more negative trim to help put the bow down. I run a Hydro with standard water pick ups 2 inches above the pad with no water preasure loss. I see u had a 200 merc before and the performance looked pretty good. If so cool I have a 200 merc I can slap on my new to me 23 CC and get it wet faster than new power .

Re: Need ideas to stop porpoising?
 

The shape of the prop can greatly affect porpoising, as well. A bow lifting prop with a boat with very little rocker in the hull will induce porpoising. Changing to a stern-lifter prop can help greatly. Judicious use of trim tabs is also a very good idea, as is carefully watching trim angle and mounting height of the engine.

Re: Need ideas to stop porpoising?
 

I talked w/the mngr of CapSante for quite a while yeaterday and he did an excellent job of patornizing me and saying my suggetion on a bow raising prop and raising the motor was expensive so, I can see they are not going to be any help. He did say that Honda does not like other mfg's props on their motors. Looks like any fix will be out of my wallet. Although he did suggest a whale tail or doel fin, said he has seen them om the big Hondas. He did say he would check on that and get back to me but I am not holding my breath. They already have been paid for the motor and installation.

Re: Need ideas to stop porpoising?
 

You need a STERN lifting prop, not BOW lifting (they're used on bass boats to get more speed)! I would think Honda would make stern lifting props to compensate for the weight of their 4-stroke engines. Dealer should be willing to raise motor for free (it's a very simple job) if he installed it, to help mitigate the problem you're having. Might be worth trying to find a Honda rep with more technical savvy!

Re: Need ideas to stop porpoising?
 

I meant to say stern lifting prop. Yeh, I would have thought they would raise the motor for me. I will wait a few days to see he calls me again before I cal him or the salesman and chew on him, but don't think he is into anything but selling.

Re: Need ideas to stop porpoising?
 

If it is a matter of raising the motor to "tweak" it that is the dealers responsibility and obilgation. If he does not think so, then so be it. You can raise the motor if you have a floor jack yourself to check different configurations. My motor installations insist on making sure the motor is at the right height and is willing to move it as much as I think? is necessary. Put pressure on the dealer to finish his job.

Re: Need ideas to stop porpoising?
 

PLEASE TRY A STERN LIFTING PROP AND GET THE CAV PLATE RIGHT. Fr.Frank and Bigshrimpin are the driving force for my doing so. It`s as if little elves redesigned my hull.
No company wants you buying other cos.stuff. When they go racing they use whatever is best. Period. I had a lot of time to look and got a very nice Mirage + for 125! The Rev 4 is an even better choice imo after Bushwacker's research.

Re: Need ideas to stop porpoising?
 

I called the salesman and told him again of my concerns. He had never heard of a stern lifting type prop and insisted that the motor cavatition plate should be 1 1/2 inches below the center lines as per specs( Honda?). Anyway I went out and checked it and it is even with "V" center. Tom Clark in Seattle was going to check to see what prop the Honda number might cross over to and what he has on hand that might work. Looks kind of like I will have to buy a used prop to try. Tom thought he had a coupl layng around his shop.

Re: Need ideas to stop porpoising?
 

If he said that, he's either:

• a completely ignorant newcomer to boating; or
• he's a complete idiot; or
• he's lying through his teeth.

There are no other plausible explanations for making such a statement.

Re: Need ideas to stop porpoising?
 

I`m in sales. Your "salesman" is a tool!

Picture this in your mind. Your cav plate is well below the keel. What really happens when you trim up? The plate digs in like a shovel and pulls the stern down. This will happen even if they are level. That`s why it needs to be higher. This is true of ALL motors. PERIOD.

This is also killing performance and mpg. Not to mention the boats running attitude. Your`s too.

Fr. Frank has forgotten more about props than most "pros" will ever know. He tested props for a living. Bushwacker was an engineer at Pratt+Whitney. Tool or rocket scientists? I`d tell the tool to come by CSC for some edumacatin!

Re: Need ideas to stop porpoising?
 

Forgot. Mirage+ and Rev 4 prps have interchangeable hubs for different brands of motors. I have a Rude w/ a Merc prop.

Re: Need ideas to stop porpoising?
 

I opened my e-mail this AM and surprise, I have an e-mail from Capt Sante, they want me to bring him the boat down and they will raise the engine. I did go out and check the boat yesterday w/a straight edge. The cavatition plate is exactly even with the flat portion of the "V" bottom of the boat. The Honda motor has the big cavatition plate and directly above it is 2 smaller plates. I am told thses are splash guards(?). I was thinking 1 or 2 holes and bring it up to about 1 1/2 inches higher. Ideas, please?
How much should I have the engine raisied by, 1 hole or 2 holes??
This is a single counter rotating engine, so I don't think that would make any difference. I am not really that knowledgable about props. The prop is installed on a spline with a new etc and carter key.
I sent Tom Clark and e-mail to see if he has come up with anything. The only numbers on the prop is S 3 14 1/4 17 L and of course the Honda name.

Re: Need ideas to stop porpoising?
 

I took pictures of the transom, now I just need to figure out how to post them here.
I have been trying to figure it out and I am not having any success. Can I e-Mail them to someone and they can maybe post. :D

Re: Need ideas to stop porpoising?
 

I'd go 1" at a time and try it out. With engine trimmed as high as possible without porpoising, you should be able to make a moderate turn at cruise speed without ventilation/cavitation, although you may have to trim it down a little for hard turns. It will also help if your prop has a fair amount of cup in it as this seems to allow you to run a higher mounting position. Years ago I switched from an aluminum to an OMC SST stainless prop, and raised engine 1" as they recommended. (Engine was originally mounted same as yours with cav plate lined up with bottom of hull.) I picked up about 3 mph in top end, as was advertised. You may find that you have to run with engine trimmed a down a little more in rough seas to prevent ventilation or cavitation.

Re: Need ideas to stop porpoising?
 

. Ok, looks like I did it!
[image]http://i44.photobucket.com/albums/f4...6/DSCN0378.jpg[/image] http://i44.photobucket.com/albums/f4...6/DSCN0377.jpg http://i44.photobucket.com/albums/f4...6/DSCN0376.jpg
http://i44.photobucket.com/albums/f4...6/DSCN0375.jpg

Re: Need ideas to stop porpoising?
 

Just an unschooled observation but it looks like a lot of negative trim there. If you are running with the trim down all the way, I believe it may be contributing to the porpoising as it will cause the nose to dive, constantly fighting the bow's desire to rise and plane. I don't know the boat or motor but if there is an angle setting adjustment, hole you may want to set the shaft a little closer to vertical - I think the angle of the cavitation plate is the first thing to straighten out as it is the first "flap" that directs your glide in the water. All the wings, foils, and trim tabs are just inefficient counter measures if the motor trim is off. Experiment with the motor trim more.

Re: Need ideas to stop porpoising?
 

The cavitation plate must be measured with it being exactly parallel to the keel. Your photos show negative trim angle. I suspect you will find the cav plate a bit below the keel and neutral trim angle.

The suggestion to raise it one mounting hole at a time is a good one, although I suspect you're going to end up raising it two holes. For an outboard, the ideal trim angle under way is with the cavitation plate perfectly parallel to the direction of travel with the hull at optimum angle of attack, and the rotating propeller blades just barely piercing the surface. Unfortunately, the only hull I've ever seen that ideal achieved with is an Allison XTB.

SO we compromise. Raise the motor, use a sternlifting prop, and play with trim angles.

BTW, a sternlifting prop is one which provides most of it's lift from the inner 1/2 of the diameter of the blade length. That's why progressive-rake 4 blades provide more sternlift than 3, and cleaver blades LOTS more sternlift than chopper or "big ear" props.

Re: Need ideas to stop porpoising?
 

The negative trim angle look in the picture is probably because the tongue of the trailer is high to accommidate hitching up to the truck. I normally try to keep the top of the motor running flat with the water or a little higher.
Tom Clark in Seattle sent me the following e-mail(s)after looking at the pictures.
That is a Turbo prop made by Precision Propeller (now owned by Yamaha).
Those are great props on smaller boats, usually very fast,
but not a great prop for a high horsepower motor on a pretty big boat.
Looking at the photos, I would recommend raising the motor two holes (1-1/2").
From the Honda propeller catalog I would recommend the OFS 4 Blade
15-1/4" x 16", Honda part number: 58334-ZY3-B16CL
I had a an e-mail from the sales guy at Cap Sante and he wants me to bring him the boat this week and will raise the motor, now I will need to work on the prop issue. I have no idea what the price difference would be on the 2 props. Any ideas? He is off on Mondays, so will contact him on Tuesday after I go salmon fishing in the morning.

Re: Need ideas to stop porpoising?
 

The OFS4 prop is actually made by PowerTech Props, and is, in my opinion, one of the 2 best props made for SeaCraft hulls. 16" pitch sounds perfect in a 4 blade. It is a heavy stern-lifting prop, very strong blades (not thin), with moderate progressive rake, allowing for a wide range of trim angles. It also happens to be the basis for the prop I ran on my 20' Seafari, although I ordered mine in a custom 3 blade 16.5" P and 15.25" diameter. I had a Merc V6 2.0L on my boat at the time, which was built to produce about 190/200 hp.

The other advice from Tom is about right. You need to get the cavitation plate above the hull bottom so that it doesn't pull the stern down while planing.

Re: Need ideas to stop porpoising?
 

1 thing at a time, looks like 2 holes to me also, then get a WOT RPM reading so you can get the correct prop pitch the first time

Re: Need ideas to stop porpoising?
 

They raised the motor 2 holes for me this morning and we ran it for about 1/2 hr. Did not get any porposing and and was able to get 5950 RPMS(range of WOT 5K-6K) out of it w/2 adults and 90 gal of fuel and the extra 60 lbs of lead in the bow, I just took the lead out as I don't think it will be needed now. I did not check the speed but plenty fast, had to dodge crab pots.
I asked about the 4 blade prop and they were not very eager to go there because of the $500+ cost. I even offered to split the difference on the price increase to swap the prop, but all I got got was no comment or we'll see.

Re: Need ideas to stop porpoising?
 

Excellent, now get back to fishing! :cool:

Re: Need ideas to stop porpoising?
 

Gosh darn this is one of the best posts as of recent. All awesome, spot on information. What a great community. Kudos to all that posted. Sounds like the dealer is stepping up to the plate. Now, get the lead out!