23" Scepter I/O performance
 

Happy New Year to all.

I was out with the dog this morning and looked over at my Scepter that I fervently hope will become a WIP (work in progress) soon. She has a 140 gal fuel tank, tabs, etc.; much like most others. I have a 260 HP volvo penta out drive on it and intend to keep it that way. I DO intend to replace the motor however and am thinking about taking up over 300 HP. Someplace between 315 and 350 depending on whether I go normal carb (somewhat repairable on the water if it should fail) or Injected (which I understand little about and less in terms of repair.) I likely may adust the fuel tankage to something a little more realistic for my purposes, say fore and aft mounted dual tanks of say 80 and 50 with the smaller mounted aft and not kept empty unless I should feel the need to carry more fuel at one time for whatever reason. By my calcs that would give substantially over 200 mile range. I live in norhern Mass. and would likely not venture more that 40 miles offshore, but I may venture as much as far down to Long Island/New York or up to Camden, ME.

My question is what are real perfomance numbers for various power options. It is no speed demon, but in the past I was cruising at 21-23 @ 3200 RPM and about 32-34 WOT. That may have been a bit conservative, but the extra two carb barrels weren't open at cruise and I was getting about 5-7 gal/hour burn rates overall.

I hope to hear from all and I wish everyone of us a better year, no matter what your 2011 was like. Be well!

the multiport engines are definatley the way to go - smooth acceleration,"turn key" starting,alarm systems keep the engine from self destructing...

last volvo repower i did - the distributor had a "left over" 5.7 gxi engine - i got a deal that was hard to beat.
i'm not a fan of replacing "long blocks",or rebuilding what's existing - i use complete "drop in" engines...reason being,you're pulling an engine that's basically worn out - the exhaust system - manifolds and risers,tin ware,pulleys,fuel system parts,electrical parts - these are all old too...transfering these old parts,onto a "rebuilt" block,or,replacing these parts and installing them onto a "rebuilt" block - this all starts to add up,and,in the end,you're got a "rebuilt" block - most of these blocks carry a very limited warranty.purchasing a new,drop in engine,it carry's a mfg's full warranty,it's new,as in new,everything on the engine is new,and,in most cases,it actually works out to be only a few dollars more.the idea of a repower is to "up grade",make the boat perform better than it did previous...
for what it's worth: the multiport injected engines have proven to be very trouble free - i've repowered numerous boats with these engines - no failures on any...

my own potter built -
it was repowered in '01 with a 5.7 merc magnum MPI with the horizon package - bravo drive.that package has proven to be incredibly efficient,and reliable - ZERO problems - cruise speed,with a full load - 150g fuel,loaded to fish offshore for the day - 22-23kts...that rig's been ran and ran hard...

Thank you, Jim. I take your points very seriously.

MPI vs. Normal aspiration is attractive and is definitely in the mix for a couple of reasons. First, it seems to be easier and quicker starting, not to mention more efficient in general. It also provides more and higher HP options for about the same money. My one real hang up is on-site repairabilty. I have esperienced sudden engine failure in the past and often it has been repairable on the spot. Stuck thottle plate, water acculmulation in the float chamber showing up as you crank up the rpms - out of close range to a dock, etc. MPI does not seem to be the same situation or maybe its just my lack of familiarty with it-NONE!

Your performance numbers are of interest. Clearly there is some expectation of increase on my part. I was thinking that going from 260 to say 330 would put me in the 26-28 rrange on cruise and the higher 30's, say 37-39 wot. Am I being unrealistic? The cruise number is the more important to me overall.

PS

Jim, I totally agree with a new engine; from fuel line to batteries to bell housing! The drive is up for grabs. It is rock solid as it sits and has a stellar history. That said, for the right reasons and the right $$$ it may be in the mix as well.


I'd also like to hear from others on this as well. Say "Entourage", " Water Rat" or someone else runnig a Scepter I/O set up?

I do know one thing. Being up north here and dealing with the local area, i.e. the Merrimac River inlet and a LOT of 2+ ft. chop as I do, I will not be going to an outboard. It is a personal thing and I just like the weight being down low in the bilge.

I have a 260 hp volvo 280 drive. I dont know why but I hate it performance wise. It is the oem motor/drive that came with the boat.(freshwater) Runs great never had any issues with it so I dont know why I hate it, just do. They are suppose to be really good drives though.

When I repower I will be going with an mpi enigine drive package. (I need to do the transom anyway)

I dont pay too much attention to the numbers but I know I run 30-33 mph on cruise and can top out about 37-38. A buddy just bought a slickcraft (ugh) with a 210 hp mercruiser with an alpha drive and he can smoke me...... till it gets rough. :)

I have a 74 23 Tsunami powered by a 260 hp 350 Mercruiser with an Alpha drive.Wide open throttle I get about 35-36 MPH on the gps.I cruise at about 25 at 3400 rpm.Now if I can just get my tach to perform properly.

I'm not all that happy with the top speed,but oh well,in every other aspect it performs flawlessly.
I spent countless hours searching for the right prop.and ended up with a 15x17 Mirage plus stainless prop.This has been a good performer for me.There is no lag at all to get on plane,and it does well across all ranges.
If money was no object when I powered it,I would have gone with the 383 stroker and a Bravo Three drive.I think the Sceptres/Tsunamis need much more power in the I/O configurations than 260hp.

Lew,& Floorboy,- Volvo has some 350 5.7's that are pretty sweet in 300 & 320 hp models available with carburetors or fuel injection.Pretty nice if you don't mind spending 10-12 grand.

Prop selection is one of my main bitches with the volvo.....Do they make any???? I can't find them if they do.

Happy New Year Big Lew. I`m still waiting for my Citgo sign.

Cheers,
GFS

Hey Lew, be careful with that Citgo sign!! Sandy will be looking for it in the Bahamas when he takes his "slacker" over later in the year at the gathering. We want to make sure he can see it from far away on the water to put his mind at ease! :) :)

Don V,

ALWAYS remember, "Possession is 9/10ths of the law!" The Citgo sign is safe and will be visible at ALL Red Sox games in the foreseeable future!!! GFS can take it to the supreme court if he wants, but it is NOT going anywhere! (Do you hear me Sandy, my friend!)?

I think it was Floorboy who mentioned availability of props for the Volvo's. I too, have had some challenge in finding a variety of available props over the years. I have a 15 x 17 as well, but they are cupped. I spun the first one and decided to replace it with a cupped verision. It was adequate, so I had the first one cupped when I had it recon'd. It had had a few dings in it and I thought it might be nice to have the confidence of having a replacement onboard - but haven't needed it!

My biggest complaint is that the stern just seems to sit deeper than it should! It has been a while, but I remember that at cruise the outer aft corner was still 2-3 inches below the surface, though the outer side was not wet. On Plane the the stern corners were below the suraface but "dry" as the water exited out and back. (Is that clear?) I will say at this point that I had to step back there and really look, so my 200 +/-lbs. were back there at that moment!

I think if you look around you will find more options than you minght think are out there. Speak with some of your local prop guys/shops and I suspect they will tell you about how they can get you anything you might want. Beware though, the price might be higher because of the lower volume- Mercs out number V/P's 10 :1 at least! Original manufactures want to keep theiy selling price down, so more are inclined to go with the merc drives.

That doesn't change that the Volvo's seem to have a better long term reliability reputation and a very loyal following.

Don V,

ALWAYS remember, "Possession is 9/10ths of the law!" The Citgo sign is safe and will be visible at ALL Red Sox games in the foreseeable future!!! GFS can take it to the supreme court if he wants, but it is NOT going anywhere! (Do you hear me Sandy, my friend!)?

I think it was Floorboy who mentioned availability of props for the Volvo's. I too, have had some challenge in finding a variety of available props over the years. I have a 15 x 17 as well, but they are cupped. I spun the first one and decided to replace it with a cupped verision. It was adequate, so I had the first one cupped when I had it recon'd. It had had a few dings in it and I thought it might be nice to have the confidence of having a replacement onboard - but haven't needed it!

My biggest complaint is that the stern just seems to sit deeper than it should! It has been a while, but I remember that at cruise the outer aft corner was still 2-3 inches below the surface, though the outer side was not wet. On Plane the the stern corners were below the suraface but "dry" as the water exited out and back. (Is that clear?) I will say at this point that I had to step back there and really look, so my 200 +/-lbs. were back there at that moment!

I think if you look around you will find more options than you might think are out there. Speak with some of your local prop guys/shops and I suspect they will tell you about how they can get you anything you might want. Beware though, the price might be higher because of the lower volume- Mercs out number V/P's 10 :1 at least! Original manufactures want to keep their selling price down, so more are inclined to go with the merc drives.

That doesn't change that the Volvo's seem to have a better long term reliability reputation and a very loyal following.

Lew,I have the same problem as you with the stern sitting lower than it should.When under power,and on plane,my boat also has the outside corners a bit under water.I think it's common with most of the I/O powered Sceptre/Tsunami models.

It's way to late now,but I wish I had used a lighter core material like coosa when I did the restore instead of plywood.
When I removed the rotted core from the rear transom cap,and got rid of the bait wells,I had loads of roving laying around,so I stupidly layed up something like ten layers of it instead of using core.I could park a car on it,but it didn't help in the weight dept.
I think if I had used a synthetic core on all the areas like the transom,hatches,cap,and deck floor.I could have saved considerable weight.
That along with the kicker motor,4 downriggers with 15lb weights and other goodies doesn't help either.The scuppers are a nightmare,thank god for plugs.
My thanks to FR.Frank and also to Prop Gods for helping me get the right prop.

The guys at Prop Gods were great to deal with.

Lew here's a few shots of the boat under power.The first shows the waterline in a troll at about 3mph,you can see how low it sits.Even when on plane the stern doesn't rise up much.
The second is under power on plane(hard to see.it's a long distance shot).and the third is coming down off plane.Water conditions were calm in the first picture,and probably about a 1-2' chop in the last two pics.

http://i2.photobucket.com/albums/y7/easy2/photo-1.png

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

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

John, I think you're right about the I/O models sitting a little lower in the water, even on plane . . . if you look at that Boating Magazine article I sent you of the tests of the I/O and OB powered Tsunami's, they had a good shot of both lightly loaded boats running together at high speed and you can clearly see the chine at the transom of the OB model! Looks like the entire outer panel was dry! The OB model had twin I-6 Mercs and the other had twin 165 I-6 Mercruisers, so the OB model would have been much lighter. Interesting that the min running angle on the I/O was a little flatter (3 degrees vs. 4 for the OB), so either the extra weight is enough further forward to shift CG further forward on the I/O, or what's more likely is that the power trim was more effective at controlling running angle on the outdrives than on the outboards.

BTW, I still have a .pdf file of that excellent 9 page article. Will be glad to forward it to anyone that wants a copy if you'll just PM me with an e-mail address. Denny

Here is mine at hull speed

http://i224.photobucket.com/albums/d...1/f0a3473a.jpg

And on plane just below cruise speed.

http://i224.photobucket.com/albums/d...1/b9b47310.jpg

Speaking of performance I know the Carla Dee "Entourage" will run 48 mph with 4 guys on board, 350 mpi b-2, Thats more like it.

She sits about the same as ours off plane.

http://i224.photobucket.com/albums/d...6_192919-1.jpg

My goal is to make mine look something like this.....

http://i224.photobucket.com/albums/d...202_224025.jpg

Denny,I think you're correct about there being enough weight forward on the Sceptre models to give them that flat running angle.I know that even without touching the tabs,I can get the boat to jump on plane extremely quick.
As you mentioned,the running differences between the I/O & OB model in that article are striking.The outboard was much higher out of the water.I would assume that if the same could be achieved with the I/O's,the speed would be increased significantly.

BTW,thanks again for that article. Funny, I just bought the original article from a seller on EBAY for $10.00.
I guess I didn't read the ad all that well,because he only sent me the article,not the entire magazine(1973 Boating).It's still kind of neat having the original article though.

Rod,That's about where mine rides as well.I'll bet you're glad you didn't remove the hardtop.She looks good.You should be receiving the light today or tomorrow,as UPS tracking says it's on time.

Anyone runnin a 4 blade?

I WANT MY SIGN! {instert emoticon of Khrushchef pounding the podium.......here|

Sandy,

You can be counted on for coming up with truly original humor. Don't you EVER die Guy!

Hey BigEasy,

I apologize for miscrediting Floorboy with regard to the prop isuue. I will definitely contact to "Prop Gods" when the time comes.

Sandy raises a good question though. Is anyone with this configuration running a 4 blade, stern lifting prop? Seems like an obvious question. I never really thought about it and that probably says more about me than anything else!

One thing I do know is that I will not give up that rock solid feeling in the nasty's that I have never felt in any other hull in this class!

yup...merc 4 blade offshore - with a little tweakin'...

Pelican,

So, what is the ride and performance like? Before and after, if you can add some dimension to that would be great. How much fuel is on board? Other factors?

Also, what are we talking about, "a little tweaking"?

ride's the same - performance is the same too - lost about 1kt on the top end
boat's normally ran "heavy",with a full load of fuel 150g
previous wheel was a merc mirage 3 blade

"tweaking" - the engine would turn the rpm i wanted,the whell went to the prop shop for some tweaking,to get the rev's i wanted.the boat will run faster,with more pitch in the wheel...

BigLew,

Sorry I'm late to the party but happy to share my thoughts. For comparison, I have a '78 Sceptre with a 7.4L Bravo One, and a full cored-glass half-tower, EZ2CY enclosure with radar arch, riggers, etc. (definitely adds some weight compared to the bimini/3 sided enclosure on before).

First thing I would check is to see if your drive can handle the additional torque of the motors you are talking about. I have some familiarity with the Volvo's, but not as much as Merc; I do know you would not want to mate any of these motors with a Merc Alpha 1 drive by comparison.

With respect to your tankage, I have two tanks also. My aft tank is around 65 useable and the forward around 45 useable. I would strongly recommend the larger tank be aft and here's why. Others here have said the Sceptre/Tsunami I/O sits and rides differently and it does. The CG on these is considerably farther forward than the CC's, especially with a hardtop and a bunch of gear in the cabin. I typically burn the fuel in my forward tank first, then use my trim and/or tabs to bring the bow further down if conditions warrant to compensate for the reduced weight up there. Works especially well on a long trip; when I suck air on my forward tank, I know I've burned less than 1/2 my capacity and I also would not want the forward tank full and the aft tank empty if I had a long way home in a big following sea.

As far as performance numbers, I may not be a good comparison. My 454 is carbed (4bbl Quadrajet) and I'm pretty certain I'm due for a carb rebuild on top of having a vacuum leak somewhere (almost 1900 hours on this block now). Between that and using my tabs a lot, my performance suffered a bit this past season (need to get a good mechanic to go through my motor - I am not one). That said, at 3000-3200, in calm conditions and depending on load, I will cruise at 22-24 knots burning 10-12 gallons/hour. 3500-3600 gives 26-28 knots, and I'm guessing 15-18 gallons/hour. If it is snotty out and I'm using a lot of tab (I have the big Kiekhafer K-Planes on my boat - like dragging two five gallon buckets behind the boat when you have them down more than a bit) all these numbers fall apart and get ugly quickly.

I think a 5.7 or 6.2 litre block, at the higher horsepower ratings, would do very well in your boat. I would not be afraid of an injected engine, you just need to educate yourself with it, and would be very careful to consider the torque and torque curve. Ideally you would find a motor that is very strong torque-wise at a cruising rpm of 3000 or so.

Or you could spend your kid's inheritance and drop in a Cummins QSB with a Konrad drive.

Good luck and feel free to ask me any questions.