Squeezing more from 5.0L 220hp

screaminfast

screaminfast

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Aug 25, 2022
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Hey All! New register to iBoats, and sorry for the long-winded post, but I've been searching and reading since I got my boat back in early July. This is my first boat but I'm a pretty big car/motorcycle junkie. It's a 99 Rinker Captiva 232 Cuddy w/ 5.0L TB5 (0L096199) and a SEI16 drive (assuming Alpha One Gen II replacement). At first we were getting maybe 38-42ish on speedo, so I suspected some issues... Being that I didn't know how well the previous owner took care of it, I figured I should do the standard tune up. I did an oil/filter change, fuel filter change, distributor cap & rotor, new NGK TR5 plugs gapped at 0.045, and sierra 8mm wires.

First time out after those changes, it seemed to run well, but didn't gain any RPM and during the trip back to the launch, the coil wire popped off the coil pack and it was misfiring. Next day, I put in a MSD Blaster 2 (8202) coil and we also switched the prop out for a Turning Point 14.25 x 17P and 701 hub.

Back out, we were now seeing about 4200-4400 and 39-40mph (GPS on iPhone) on pretty choppy Lake Ontario, The motor ran very strong and everything seems to be good, but I want a little more out of it. The motor plate obviously says 4400-4800, so I'm just at the low end of that.

After reading the sticky threads on WOT RPM, I'm thinking the only thing left to check is if the throttle cable is allowing the carb to go fully open. Besides that, and since I'm not ready to investigate swapping a 350 short block into it, I was thinking a summit racing intake manifold and Edelbrock 1409 carb.

Any other ideas? Typically, we run with 3 adults and 2 kids on board, so maybe we're just loaded up for the power of this engine?

Thanks!
 
Rick Stephens

Rick Stephens

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Aug 13, 2013
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Welcome to iBoats.

First thought is, big heavy boat, lots of stuff in it, minimum HP motor for that size boat. And then, too steep pitch on your new prop making it borderline lugging. Addressing each of those:

Your top speed isn't all that off from what you'd expect from a 5.0L in a 23+ ft boat. You can build up more HP. Stick a 350 or a 383 stroker in it. Be amazed what more torque will do for performance.

Go to a prop that when the boat is not loaded all the way up, will blow up to, and through 4800 RPM. Less pitch for sure will perform better! Boats are different than cars and trucks - they are under 100% load 100% of the time.. Like running a pickup loaded, up hill, and only have 4th gear. Pick a prop that keeps you in the sweet spot even when loaded up with gear and family.

Rick
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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do a compression test.

my Searay 190 (smaller boat, same motor/drive) would hit 5000 RPM with a 19P and be just shy of 50mph per the GPS (49.5ish). make sure your drive is the 1.62:1

However you are 4100# dry weight, that is a lot of boat, half a ton more than my Searay

you may simply need more motor

not a lot you can do shy of a supercharger on the 305 as you are 220 at the prop and about 240 at the motor. a 4 barrel intake/carb and cam will get you most 275-280 at the motor (about 255-260 at the prop). the 350 does get you about 50-70 more ft-lb of torque, and the 377/383 gets you 100-125 lb-ft more than what you have now

forget the traditional car hot-rod stuff you may know being a bike/car junkie.

put your dump-truck motor / RV hat on when thinking boat motors. and remember, what ever you do, no overlap on the cam or you spend more on exhaust than you do the motor to keep reversion at bay.
 
screaminfast

screaminfast

Cadet
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Aug 25, 2022
Messages
15
Appreciate the replies! I forgot to mention that I had started with a beat-up 14.5x19P prop.

I will double check on the drive ratio and compression test/timing but it sounds like I’m at about peak with what I’ve got.

I guess the good thing is that if I decide to do the carb/intake manifold, it’ll swap over to a 5.7 or 383 short block. Will I see any gains without doing a CAM?

And in the end, I don’t want to destroy the outdrive with too much power either.
 
Bondo

Bondo

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Besides that, and since I'm not ready to investigate swapping a 350 short block into it, I was thinking a summit racing intake manifold and Edelbrock 1409 carb.
Click to expand...
Ayuh,...... Welcome Aboard,...... What carb is on it now,..??

'n you Don't want a "Racing"intake,....
Yer motor's redline is 4800/ 5 grand,..... not 6 or 7 grand,....

For a 4bbl. you want a mid- hi-rise dual plane intake,.....
Cast iron is preferred, but ya might get by with aluminum in Lake Ontario,.....

The alpha holds up Ok with a 350, up to 300 horse,....
With a 383, when the drive pukes, it's "Operator Error",...... ;)
 
screaminfast

screaminfast

Cadet
Joined
Aug 25, 2022
Messages
15
Bondo said:
Ayuh,...... Welcome Aboard,...... What carb is on it now,..??

'n you Don't want a "Racing"intake,....
Yer motor's redline is 4800/ 5 grand,..... not 6 or 7 grand,....

For a 4bbl. you want a mid- hi-rise dual plane intake,.....
Cast iron is preferred, but ya might get by with aluminum in Lake Ontario,.....

The alpha holds up Ok with a 350, up to 300 horse,....
With a 383, when the drive pukes, it's "Operator Error",...... ;)
Click to expand...

Yeah I was looking at this one: https://www.summitracing.com/parts/sum-226019

Seemed reasonably priced over doing a edelbrock marine one with the brass inserts seeing as though it’ll only see upstate NY waters.
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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screaminfast said:
I decide to do the carb/intake manifold, it’ll swap over to a 5.7 or 383 short block.
Click to expand...
You will need a long block (complete with Vortec Heads)

The small chambers and small valves in the 305 heads do not work well on a 350 or larger motor. And if you put the big valve heads on a 305, you shroud the valves
 
screaminfast

screaminfast

Cadet
Joined
Aug 25, 2022
Messages
15
Ok I’ll keep doing some research and enjoy the boat. Didn’t realize how much would be involved LOL. I figured I’d be ok considering I manufacture firearms.
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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screaminfast said:
I figured I’d be ok considering I manufacture firearms.
Click to expand...
Depends if you are developing gas piston conversions for the military or just tinkering with known designs

Understanding motors is no harder than understanding semi-automatic gas-piston actuated firearms
 
screaminfast

screaminfast

Cadet
Joined
Aug 25, 2022
Messages
15
Bondo said:
In NYS,..??..?? I lived in Chaumont, on the water till 3 years ago,....
kathy is crazier than andy was, 'n that's Crazy,....
Click to expand...

Yeah man she is nuts. Only have to stick it out for another 4-5 years for the kids to finish school.
 
screaminfast

screaminfast

Cadet
Joined
Aug 25, 2022
Messages
15
Scott Danforth said:
Depends if you are developing gas piston conversions for the military or just tinkering with known designs

Understanding motors is no harder than understanding semi-automatic gas-piston actuated firearms
Click to expand...

Haha true story. We manufacture receivers and small parts for ARs. 3 CNC machines but we’re pretty small. We have a couple LE dept contracts and a separate retail store.

Most of the car/bike stuff I’ve done has been turbo BMW’s so carbs are a mystery to me for whatever reason. We share our retail store space with an engine builder who does a lot of boats and he 100% said to do the 350ci swap too.
 
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