truck cam or marine cam?

[lime4x4]

Decided to just replace the engine in my 86 mercruiser 5.7 with a 91 engine from a truck that was rebuilt last year and never used.I know i have to change the freeze out plugs to the brass plugs.Do i also have to change the cam.Some say as long as it's a truck cam i'm alright.The boat weighs around 5400 lbs dry or should i replace the cam with a performance cam and if so where do i get one for a marine engine?

 

[Coors]

Re: truck cam or marine cam?

It's hard to tell what cam is in it with out pulling out the degree wheels and dial indicators. How do you know?

 

[Coors]

Re: truck cam or marine cam?

And do you have all the needed marine starter, alt, carb, fuel pump, dist, etc? After my dealings , when I was new to i/o; a shade tree mech got me good. I don't trust anything unless I see or install it.

 

[lime4x4]

Re: truck cam or marine cam?

Yes i have all the marine stuff.From the engine i pulled out of my boat today.I know the engine cause i rebuilt last year for a job at work then the cust changed his mind.It was for a 91 1/2 ton truck and i used all gm parts during the rebuild.Just can't remember if it was 4 bolt main cap or not.Which i don't think that matters.I know a factory mercruiser cam is outrages in price.

 

[Coors]

Re: truck cam or marine cam?

Sounds like you are good to go.

 

[whywhyzed]

Re: truck cam or marine cam?

87 vs. 91 - I think the 1 pc rear main seal happenned in that time frame. You might have to convert to a different coupler, maybe flywheel etc....

 

[Bondo]

Re: truck cam or marine cam?

Sounds like you are good to go.

Ayuh,.........................

 

[lime4x4]

Re: truck cam or marine cam?

the engine i took out has a one piece rear main seal and the boat is an 1986 so i'm thinking the block was changed. The engine that was currently in the boat will need a new crank,bearings and 2 rods plus gaskets.I've been reading on some other websites that say auto engines don't last long in marine applications.tomorrow i'll go over to napa and c what a crank kit and rods and gaskets will cost then make a decision on what i will do.I did notice that the pistons in my current engine are different then a stock chevy engine.maybe i'll i'll just the crankshaft and bearings from the rebuilt truck engine.I know the crank is forged which is a must for a marine engine.I'm planning on using this boat for offshore fishing.

 

[RCSConstruction]

Re: truck cam or marine cam?

.I've been reading on some other websites that say auto engines don't last long in marine applications.

I did a TON of research on this and the bottom line is.... They are the same dang thing. I even emailed Michigan and Rapid-O marine and they both said the only difference is price and warranty. Only thing I would make sure was that the head gaskets are marine grade or at least have a stainless steel fire ring in it.
Don't be fooled, they are 99.9% similar.

 

[SuperNova]

Re: truck cam or marine cam?

Thank you RCS, that's exactly what I've been preaching. The only things you have to do to a marine engine is brass freeze plugs and composite headgaskets with a stainless fire ring. Even the cams are exactly the same. The B.S. about marine cams being different is crap. I have a '99 5.7 out of a Searay sitting in my shed right now that is a 2 bolt main, cast crank, sintered iron rods with cracked caps, cast pistons, GM cam that has the same part number they used in light trucks and passenger cars. The only hard lesson I learned about building marine engines is 3/8" screw in rocker studs don't hold up at 5000 rpm for more than 5 or 10 minutess unless they are TOP quality (ARP or B&B). Amen and Hallelujah, Brother!!!!
--Stan

 

[lime4x4]

Re: truck cam or marine cam?

Well i got the old blown engine disassembled.Spun 3 rods and 6 cylinders look like they have cracks in them.The pistons were marked .040 so i'm assuming this poor 350 block was bored .040" over.Cam and cylinder heads are reusable.But lookes like this project is on the back burner.All the local boat dealers in my area have no cylinder head gaskets.One dealer said there back ordered with no date for delivery.would a set of top of the line felpro head gaskets work??boat will be used in freshwater 90% of the time.the other 10% will be saltwater.

 

[RCSConstruction]

Re: truck cam or marine cam?

One dealer said there back ordered with no date for delivery.would a set of top of the line felpro head gaskets work??boat will be used in freshwater 90% of the time.the other 10% will be saltwater.

My "marine" motor came with the blue felpro permatorque gaskets.
Felpro also makes marine gaskets as well.

 

[SuperNova]

Re: truck cam or marine cam?

I used the Fel-Pro permatorques in every engine I ever did, never had a problem, even when using aluminum heads on a marine engine.
--
Stan

 

[Bondo]

Re: truck cam or marine cam?

Ayuh,...........

If you're going to Rebuild your motor,.....
Ya Gotta Quit shopping at Marinas,+ Find yourself a Quality Parts House........


Btw,...... The Forged Crankshaft is Also a Major Fallacy..............
I Doubt your 86 is...... Unless it's from the Mercruy Racing div......

 

[lime4x4]

Re: truck cam or marine cam?

I know.Local auto parts store can only get me the marine grade gaskets if i want to wait a week.the local marina called today and told me he got the head gaskets in.So i'm good to go..