Choosing an engine to replace 3.7(Long)

PatinIdaho

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Last fall i bought a 1986 Blue Water 19F Executive open bow boat. Has a 3.7L(470) 190HP Alpha 1.
Runs good, Starts easy but has the broken charge system and i now have the Alt conversion for it.
So this is more a fun project and nothing that needs done, Just a because i want to project. I Can collect all the parts up over the summer and next winter do the swap.
Question i have is this.
According to IBoat spec the boat weighs 2200# and is rated for 230HP max. I can not find a word about it otherwise on the internet.
Between a 96 or newer 4.3L or a 5.7(any year) What would you do? I have access to either engine for cheap enough and will have either rebuilt to marine spec.
I know with a newer 4.3L i will need to move to a Alpha 1 Gen 2 setup,exhaust and all the other little stuff. I think it will all work the existing keyhole?
I believe if i go with a older 350 i would need a new bell housing,flywheel,coupler and upper transmission along with the associated exhaust parts?.
I never pull skiers, once or twice a summer ill pull a tube.
Usually i like to cruise around 30/35MPH 3K RPM from my past experience with boats that seems to be close to the sweet spot but sometimes opening them up sure is fun when the wife is not with ya:)
Im personally leaning to the 350 but want opinions. Im not bleeding money but this is something i can afford if i start off going in the right direction to start with.
Thanks guys!
 

Scott Danforth

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first, you may want to verify the max loading as generally hp limits are on outboards.

if it was me, i would probably find a 4.3/A1G2 and drop in to replace the 470 you have. however that is also the same amount of work to drop in a 5.7/A1G2

if you go with any V-engine, you will need to swap out a bunch of parts. easiest is to unbolt what you have, sell it off...... then source a complete motor/drive (complete, as in missing nothing)
 

PatinIdaho

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Hi thanks for your thought on this.
I have thought about what you have suggested but i don't think around here i will find the boat i need. Around here you can sell a total POS boat for 2k with what i need and still need to rebuild the engine. so it will probably be easier to piece it together off ebay.
Part of the reason im leaning to the V8.

I do have a 1986 350 sitting in my garage for the last 5 years(needs rebuilt). Using that engine i can reuse some of the alpha 1 parts. Will need to buy PS bracket and lines, Bell housing, Exhaust manifolds, Flywheel, Coupler, Y pipe, Upper transmission, Motor mounts and a few other little things i can't think of right now.

Saturday im buying a good running 97 4.3L from a friend for $100. I would have it rebuilt also. Then i need a complete Alpha 1G2 setup, 4bbl intake new carb, Exhaust manifolds. Will be a significant jump in price.

Ill have both engines and can go either way right now. So for now im watching CL and see if anything pops up to get me started in one direction or the other.
 

Bondo

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Then i need a complete Alpha 1G2 setup,

Naw,...... The Alpha ya got will run with that motor, even the gear ratio will work,......

Ya just need the Marine hardware for the motor, 'n a y-pipe for yer Alpha,....
 

QBhoy

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Hi. Not so long ago, a friend had the same thoughts. He had been through 2 or 3 470 engines and had enough. He planned to drop a 4.3 in. After a bit of research, he decided just to put a new 3.0 in. Simply because this way, he didn’t need to change the gearing (or prop at least) and more crucially, the engine mounts and all the other issues that go with. The 3.0 just went straight in where the 3.7 came out. There surprisingly wasn’t a great deal of performance drop. Ran within 1/2mph and only a little slower to plane.
 

PatinIdaho

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Naw,...... The Alpha ya got will run with that motor, even the gear ratio will work,......

Ya just need the Marine hardware for the motor, 'n a y-pipe for yer Alpha,....

Really? From reading here i was under the impression you could not make a newer 4.3L bolt up to a old Alpha 1.
If im wrong and you can i will surly use the 97 4.3L!

QBhoy. Thanks for mentioning that but im dealing with the two engine choices i have.
 

Bondo

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Ayuh,..... A bobtail motor, a 4.3l in yer case, from 'bout '83, to current production can be interchanged, 'n will mount to the drive,.....
 

HT32BSX115

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Part of the reason im leaning to the V8.

I do have a 1986 350 sitting in my garage for the last 5 years(needs rebuilt). Using that engine i can reuse some of the alpha 1 parts. Will need to buy PS bracket and lines, Bell housing, Exhaust manifolds, Flywheel, Coupler, Y pipe, Upper transmission, Motor mounts and a few other little things i can't think of right now.
You'll likely need a different ratio drive (1.5:1) and other parts to use the V8 efficiently.

Having said that, If I had a choice and time to collect parts, I would go with the 350 V-8 hands down.

Usually i like to cruise around 30/35MPH

Cruising fuel burn (assuming you're going approx the same speed you indicated), will be approx the same regardless of whats turning the drive shaft. (4cyl, 6cyl, 8cyl) If you like running around at WOT more frequently, fuel burn will follow your "right hand"!

But for other things like hole-shot and acceleration, there's NO substitute for cu-in.

You'll never be unhappy with MORE power!

Cheers,


Rick
 

PatinIdaho

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Gathering a list of the V6 parts i will need to order and there is a couple things i can't figure out.
What exhaust Y pipe i will need. Only use Alpha1 or will gen 2 also work?
What flywheel. 14in, 168 tooth?
What thermostat housing?. Sooo many different styles!
Is there a way to use my current 4in heat exchanger on the V6. I believe so but will need to add a expansion tank to the cooling system.
I believe i have everything else figured out.
 

QBhoy

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Ditch the fw cooling idea. Not required and not worth the effort I’d think. The different engine mounts, possible drive ratio change (might be lucky), certain prop change, electrical system and exhaust system change will keep you busy enough. Hope it all goes well and keep us updated. 4.3 is likely my favourite engine of all time.
 

PatinIdaho

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Thought no one was interested :)
So here is where my project is at, at the moment
Bought a 94/95 running 4.3 with 102K on it for $100 No ridge in the cylinders after taking the heads off and there is still a hint of the crosshatch pattern in the cylinders.
Contemplating just tossing new rings, rods, mains in the short block VS Reman shortblock
Will be picking up some 96 or later heads and having then rebuilt but unsure what i should have the machine shop do to them above a standard rebuild?

Now some really good news.
Put a ad on CL looking for a trashed but COMPLETE boat. either V6 or V8 and a guy contacted me saying he had what i was looking for.
After a few TXT's we met and i bought a 1991 20FT Blue Water full of pine needles bad interior and a engine with a rod knock for $500.
4.3 2BBL, Alpha 1 Gen 2. Out drive has clean oil.
The boat is actually solid and with a new engine/interior i would ask 4K for it(Yes i can sew and have re done a couple boat interiors) So for 2K i could make about 2K off it but i don't wanna do the work(Lazy me)
Anyway so the plan is to strip it completely and take it to the dump for disposal ($100) Leaving me with ALL the parts i need and a VERY nice 19/22F EZ Loader trailer to sell for around $800. Now if it would juST STOP RAINING!
Anyway thats where the project is at. Should probably post in the engine forum about how to rebuild the 94/95 engine to get the most out of it within reason.
 

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Scott Danforth

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Your trying to mix different generations of 4.3s

It will cost you more in the long run to do that

The 94 or 95 motor is a balance shaft motor
the 1991 is a non balance shaft motor

You cant use the flywheel, damper or acceasory drive from the 88-91 motors on the 92-95 motors

The heads are the same, however that is about it.

I would pull the 91 apart and fix the rod knock, then get 96 or later vortec heads and convert to adjustable valvetrain. Or find a 93 - 95 boat to get the motor parts if you want to use the 94 or 95 block you have
 

PatinIdaho

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Your trying to mix different generations of 4.3s

I would pull the 91 apart and fix the rod knock, then get 96 or later vortec heads and convert to adjustable valvetrain. Or find a 93 - 95 boat to get the motor parts if you want to use the 94 or 95 block you have

Was hoping you would pop in. Thats the plan then.
Rebuild/Reman the 91 with Vortex heads and screw in studs. Edelbrock 4BBl intake/carb.
What other modifications would you suggest?
 

Scott Danforth

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Pay to have the motor balanced if you need to rebuild

New crank is about same cost as reconditioning your current. However it could simply be ujoint knock vs rod knock

carb spacer helps low to mid range
 

PatinIdaho

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Doubt i could get that lucky. Have the receipt from when the drive was serviced including new bellows last spring.
 

Lou C

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One plus I see there on the one in the boat is that appears to have closed cooling, if not full of rust it may be worth a rebuild vs another raw water cooled engine out of another boat...
 

PatinIdaho

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One plus I see there on the one in the boat is that appears to have closed cooling, if not full of rust it may be worth a rebuild vs another raw water cooled engine out of another boat...

It has closed cooling and a cabin heater. Need to figure out how to put the cabin heater in the boat its all going into ;) I have never seen rust/corrosion be a problem on trailerd boats around here. Fresh water for hundreds of miles.

Had the bad engine started up today and there is definitely a noise. At idle NO noise and 45PSI oil pressure slightly warm. off idle there is a noise that comes and goes. Forgot to look at the oil pressure when revving :(
Been along time sense i herd a rod knock but the noise was not really crank/rod speed.
Sounded almost tinny but did sound like it was near the front and internal. Spose maybe a piston rattling or maybe a dropped valve but it did seem to idle smooth and no blue oil burning smoke or blow by out the valve covers.
Just thought of this. Has 600hrs on it. Maybe the timing chain slapping against the cover. Possible?
One other possibility i can think of. The fuel pump is not pumping fuel maybe the fuel pump cam thing is broke and making the noise.
 
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