AND another 4.3 engine swap * from my truck to my boat

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RiggerMark

Seaman Apprentice
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Aug 13, 2011
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good day,
so if ya saw my oil pics, you know what the next step is, and to give an idea of what the heck I'm doing, I brought and installed a low miles 4.3 in my gmc work van back in april, brought from ppl I know, runs great in the van, but I never got around to getting the van on the road, ie didn't need it yet, been a busy summer work wise, so I figured I'd get around to it this fall,
And so, finally got the wife to go out on my 1963 14' Mermaid V-hull, 1985 25hp seahorse, she loved it, had a blast just running around, now this is the first of june, guess what she said the next morning, let's get a bigger boat, a bowrider even, anyhow, here we are, 1985 Starcraft CSS180, 4.3 GMC with OMC outdrive, it's in really good shape, new floor done well, seats all good, foams all good, just a really nice boat, the engine and drive looks taken care of, (we know better), found it on craigslist, needs a starter and a "freeze plug put back in" huh? sounds like trouble to me, so I bought it, the guy kinda knew what was going on, hadn't been able to sell because of the freeze plug issue, I made a project type offer and he accepted. Set in my drive for 2 weeks while I was busy with work, started messing with it this monday, you can go read my" see my oil" thread :D, and read that part, sooo, to make a long story, I've already removed the 4.3 back out of my van and started pulling the 4.3 out of the boat, would like to get the heads to a shop as soon as possible, I will marinize the motor as much as possible, all but the cam, going to leave it alone, I know there's different thoughts on auto verses marine, some folks say that everything is tougher, better, stronger in a marine engine, but I know that both blocks look exactly the same, 3 yrs. apart, both say GMC 4.3L and I guess the rest we'll find out, going to try to share pics and knowledge as I go, once again iboats, thanks, Mark
 

stackz

Master Chief Petty Officer
Joined
May 29, 2008
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830
Re: AND another 4.3 engine swap * from my truck to my boat

if you're pulling the heads for the shop, just go ahead and pull the timing cover off, pop out the lifters, and slide the cam out and swap it for the marine cam. I have no idea about the other thread but I'm guessing the original block is cracked letting oil/water mix?

doubt that took much of a toll on the original marine cam. toss on a new timing chain while you're at it.

I didnt believe marine cams were that much until I started looking up cam cards for marine/auto cams with the same advertised lift/duration. completely different and will toss your power curve right out the window. ramp rates are different across the lobes being one of the main things I noticed. lobe separation is generally tighter even though duration increases for marine compared to auto as well.
 

HopinImFloatin

Petty Officer 2nd Class
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Sep 21, 2010
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Re: AND another 4.3 engine swap * from my truck to my boat

careful with the "3 year difference". Right aroung that year, 86, i believe, gm went to a 1 piece rear main seal , 85 was not. I could be mistaken with the exact year but flywheel and possibly coupler will be different.
 

proshadetree

Lieutenant Commander
Joined
Jul 19, 2008
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1,887
Re: AND another 4.3 engine swap * from my truck to my boat

Truck cams dont make much difference. I run in fresh water like I suppose you will being from TN. I swapped the intake, oil pan and windage tray with the correct pickup to my junkyard small block years ago. Been running like a top. If 50 MPH in a 19 foot cuddy is running good. In fresh water steel freeze plugs are OK. Automotive head gaskets are too. Just make sure and dont use automotive carburetors, alternators, and starters on a boat. You might get away with it for years but why chance it? Did I mention we like pics?
 

Bondo

Moderator
Staff member
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70,652
Re: AND another 4.3 engine swap * from my truck to my boat

careful with the "3 year difference". Right aroung that year, 86, i believe, gm went to a 1 piece rear main seal , 85 was not. I could be mistaken with the exact year but flywheel and possibly coupler will be different.

Ayuh,.... That's gonna be a real Problem....

I wouldn't worry 'bout the cam,.... at All....
 

RogersJetboat454

Commander
Joined
Jul 9, 2010
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2,964
Re: AND another 4.3 engine swap * from my truck to my boat

I'm a guessing the OP was ultimately successful, or didn't do it and hasn't been around these parts since August 18th of last year... ;)
 
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