Man oh man, what a ride.
 

Well,I finally got a chance to sea trial my Tsunami,and all I can say is "WOW".
It's been fairly nasty on the great lakes(lake Ontario),where I now have the boat.The last few days the seas have been 3 to 8 foot waves very close together,which unfortunately,seems to be the norm,every time I get there.

Today we came in in a very steep chop of at least three footers,spaced very close together,and I,along with my friends,were blown away by the ride.
I was able to get on plane,and ride on top of these without pounding.It was unbelievable,the faster I went,the better the ride actually got.
I did have a couple hard landings,when I wasn't paying attention,and in a bit of a quartering sea,but this boat is everything it's said to be.

I found that the tabs are a huge help for getting the bow down where it needs to be in these conditions.

I have a 350 Mercruiser in it with a 4bbl carb that puts out approx 275 HP.
The one thing that I'm a little unhappy with is that my top speed is only around 33 MPH,at 4400 rpms(that's max rpms),and at about 3400 Rpms,it's around 26 Mph.

I'm spinning a 14-1/2 X 17 prop.I'm wondering if the out drive needs a gear change.
Currently,It's a 1.65 to 1 gear ratio,but my marine mechanic says that I would be much better off with a 1.50 to 1 gear ratio.

Anyone have any advice?would it be worth the cost,and would it improve the performance significantly?.

Anyway,I still can't beleive how awesome the ride is.and I am in my glory with this boat.
If anyone has any input regarding the gear ratio change,it would be appreciated.

Re: Man oh man, what a ride.
 

I have a 1.5 on a Bravo 1 but it's on an 18 degree deadrise 24WAC (Sportcraft). It has a 350MAG Horizon with a WOT rating of 5200RPMs and I can hit 5150 with a 15 pitch Rev 4 for a top speed of about 41. Cruise at 3600 RPMs is about 27MPH for abou 2.7mpg. Dropping the gear ratio I think will move you to a lower pitch prop to hit your WOT rpms. I don't know that it would improve your overall performance.......maybe Fr Frank will chime in ;) What kind of prop is it??

Re: Man oh man, what a ride.
 

Congrats on splashin' her, John. :cool: That red Tsunami's gonna be the envy of Lake Ontario. I can't give you much advice on performance, but find out exactly what prop you have and tinker with that first. Also, was your speed reading gps, or paddlewheel; and was it reading knots or mph?

Re: Man oh man, what a ride.
 

Thanks guys,
The speed was on my GPS. The top speed was about 33.
I probably could have got a little more,if I played with the tabs,but I still don't think it would have increased all that much.

If anyone has any advice regarding an out drive gear change feel free to chime in.

here's a few pics.

http://i2.photobucket.com/albums/y7/easy2/100_2385.jpg
http://i2.photobucket.com/albums/y7/easy2/100_2386.jpg

http://i2.photobucket.com/albums/y7/easy2/100_2384.jpg
http://i2.photobucket.com/albums/y7/easy2/100_2387.jpg
http://i2.photobucket.com/albums/y7/easy2/100_2388.jpg

Re: Man oh man, what a ride.
 

Looks Awesome John! :cool:

Re: Man oh man, what a ride.
 

That does just look awesome.....

Re: Man oh man, what a ride.
 

Nothing looks better than an SC that's out in full FISHING MODE. Great shots John!

Re: Man oh man, what a ride.
 

John,
The ride really is something. Ten years ago when my father bought his 23' Sceptre, he had stepped up from a 20' Wellcraft V20 CC. That first ride on the SC in similar conditions that you describe was incredible - we braced for re-entry and nothing but a soft landing.

Regarding your speed, I would think you could get more out of that setup. A fellow CSC member and family friend has an '85 Sceptre with a 260hp Merc 350 and Alpha drive. Not sure of RPMs or prop size, but he consistently runs mid 20s cruise and a 40-41mph top end.

Re: Man oh man, what a ride.
 

Great looking boat John! Glad to see you finally got her launched!

Regarding performance, I think you've already got the right gear ratio and that a change to a 1.5 would be going in the wrong direction. Unless you're running a very light high speed boat, a larger diameter/slower turning prop is generally more efficient. I think that's one advantage the 4-stroke Zuke's have over their competition - they get some extra gear reduction between the crank and drive shaft, so they can spin a larger prop. If that engine is new, it may still be a little tight also, so you may pick up some more rpm after getting some more hours on it. I'd focus on a prop change, maybe less pitch and a little more diameter. Stay with aluminum to keep the cost down until you get it dialed in. A good prop shop can also repitch an aluminum prop by a couple of inches for not too much money.

The reason I say the 1.65 is the better ratio is that a friend of mine that owned the SeaCraft 21 "Unohu" (see Proud Owners section of Carla's web site) did a major repower back in about 1975 from an I-6 Mercruiser to a 350 V-8, rated at 250 hp. His mechanic was Frank Brown at Brown & Hauptner Marine, who used to crew for Carl Moesly on some of his race boats, and was one of the best mechanics around at the time. The standard ratio on that setup was 1.5:1. Frank asked Bob if he would mind if he tried an experiment where he'd swap out the 1.5 gearbox for a 1.65 at no cost when he installed the new package. Bob said go for it, and was very pleased with the results. The most convincing part of this story is that the following year, that hp rating on that exact same package went up to 260 or 265 hp - the only change . . . a 1.65 gear instead of a 1.5! :eek:

With a heavy Bahamas-trip load the Unohu would cruise at 20 kts at an easy 9" of manifold vacuum and run over 40 kts @ WOT. (Frank said max continuous power was 5", so don't cruise any lower than that if you want a long life on the exhaust valves, which is generally the weak link on most 4-S engines!)

All the engineers at Pratt & Whitney that I worked with that ran inboards had installed vacuum gages and ran the engines to manifold vacuum. A plot of vacuum vs speed should help you find the "sweet spot" (most efficient trim & speed) on any inboard rig. I'm frankly amazed that no one on this site running inboards and discussing props seems to pay attention to manifold vacuum, because it provides a wealth of information. They're a very good indicator of engine load and health and can detect even minor changes in engine performance. I even use them on my vehicles, and if I was running a 4-stroke outboard I'd have one on it too! Generally the prop that allows the engine to wind up to it's rated rpm @ WOT will also give you the highest vacuum at cruise. I'd recommend installing a vacuum gage; with the existing prop you should start seeing higher vacuum at a given rpm as the engine breaks in. I would then record vacuum as well as speed vs rpm when you try a different prop. Should be a big help in getting her dialed in! Denny

Re: Man oh man, what a ride.
 

I agree.

Re: Man oh man, what a ride.
 

Nice job! You should be causing the fish to surrender with that battlewagon.......

Re: Man oh man, what a ride.
 

Try different props, They are a lot less expensive than a gear change. What is your engines suggested max RPM? that is avery important factor.

Re: Man oh man, what a ride.
 

The prop I have on now,is right on,or at least as close as I can get.
I'm hitting my engines max rpms(around 4400 to 4600 rpms),at wide open,and cruising at approx 24-25 mph at 3400 to 3600 rpms.speed is on the Gps.

I'd lose rpms,if i step up to a steeper pitch.My Mechanic,who is a friend of mine,and who would do a gear change for very little money,tells me that 1.50 is the proper gear for that engine and drive,and that the rig would perform better,with a higher top end,and better cruise speed.
He works almost exclusively on I/O powered boats,and I trust him.
He has an upper unit that he would install and let me try out,to see if I like it,at N/C.
He rode on this boat years ago,before i bought it,when it had a 351 Ford in it with a 1.50 drive,and claims it was quite a bit quicker.
The current engine is a 350 with a Edelbrock 4bbl and is in extremely good condition,with perfect compression and very few hours.
It should be equal in hp to the 351 ford that was in it before.

I just think that I should be able to get a higher top end,and a faster cruise at less Rpms.I was wondering if anyone had the same setup.

Here's the pics I deleted by mistake

http://i2.photobucket.com/albums/y7/...i/100_2385.jpg
http://i2.photobucket.com/albums/y7/...i/100_2387.jpg

Re: Man oh man, what a ride.
 

Hey John,
Boat looks sweet.Great pics.
I too am impressed with the ride on my Sceptre coming from a Mako 228.You are absolutely right about increasing speed in a chop to smooth out the ride.She also doesn't roll as much at drift like my Mako did.These 23 Seacrafts have that "big boat feel" to them.
Jerry

Re: Man oh man, what a ride.
 

That is such a great looking boat...I like the enclosure with arch...seems the perfect blend or protection, weight and function....

Re: Man oh man, what a ride.
 

John,
You may want to reconsider Denny's suggestion re. the gear change, and experiment a little with props. Determine exactly what your prop is and what it is designed to do. I know you mentioned your mechanic's comment about the previous config being quicker and faster, but was it set up for hardcore fishing like your beauty? And was the prop the same. Any number of props can get you the right rpm range but they will all get different performance numbers.

You are running a heavy boat with a heavy fishing load, and a parachute of a top. Even so I can't help but think you can get more top end out of your power package. I really think the answer is in your propping.

I went to a Merc Black Max (for its stern lifting attributes) and was very pleased. Best 100 bucks I've spent so far.

Before testing I added 4-500 more lbs of gear, water, and gas than I ran on my last tests with the old MWC Vortex, and after changing props I gained 3mph and much better cruise performance in the 3000-4000 rpm range. I haven't done an economy test yet because my flow meter was on the blink.

Good luck achieving your target speed and have fun slamming the Salmonids.

Re: Man oh man, what a ride.
 

Your gear ratio is fine. Your prop needs changing.

Allow me to use a pickup truck as an analogy. The differential gearing is analogous to the lower unit gearing, and the tire diameter is analogous to the propeller pitch.

If I want to apply torque to the pavement more quickly I can change out the gears in my differential from the current 3.73:1 to 4.10:1 gears. If I do this, I will have better acceleration under load, higher rpms at cruise, lower axle rotation for a given rpm, and better responsiveness to power inputs.

OR, I can change my tires on the rear to a smaller diameter tire, which changes my applied drive ratio just like changing the diff gearing. Dropping from my current 265x75-16 tires to 245x65-16 tires gives me almost the exact same effective results as changing to 4.10 gears.

On the other hand, if I want to have lower rpms at cruise and a higher top speed, I can change the diff gearing to the optional 3.45:1 gears. This will reduce my acceleration, but give me lower rpms at a given speed, and probably increase my top speed.

OR, I can change my tires on the rear to a larger diameter tire, which changes my applied drive ratio just like changing the diff gearing. Increasing from my current 265x75-16 tires to 285x70-16 tires gives me almost the exact same effective results as changing to 3.45 gears.

In both cases, changing the tire size when it comes time to replace the tires costs a lot less, and produces the same results.

If your current gearset is undamaged, you can more economically change your effective power to thrust ratio by just changing the prop size.

Re: Man oh man, what a ride.
 

This is the best analogy I have seen on the prop discussion...I now understand.

Thanks,