marine vs automotive engines

[Maddoxsdaddy]

Little bit of a long story.
I'll start this thread by first saying i'm on a fairly tight $2000 budget and need to rebuild or replace my motor. It's a 1995 5.7 V-8... non-vortec. It was a rebuilt motor when i bought the boat. Either it bent a wrist pin or spun a rod bearing.
With my budget, i still need to replace my trim cylinders and repair serious slop in my gimbal ring.

After doing some pricing, rebuilding will cost be around 2 grand and so will a cheap marine long block. I don't like the idea of getting an engine from a "big box engine builder"... just my .02 cents.

I have come across a 1996 complete (minus intake) vortec motor from a police interceptor with only 3500 miles from a reputable motor builder who had this motor sitting in his garage lookiing for a new home. The motor was pulled at a local dealer for a warranty issue (bad lifter) and replaced with a new motor because the police dept didnt want to deal with tearing the engine apart... yadda yadda yadda. I already have new roller lifters for the motor.

Here are my questions...
1) i've heard... don't put a car motor in a boat. Can i change the head gaskets, valves and springs in the heads, put in a marine cam and be ok? I will still use all my other marine components (carb, distributor, all other accessories)

2) It there a difference in the actual block, pistons, rods, crank, etc between marine motors and automotive motors?

Thanks,
TB

 

[Bondo]

Re: marine vs automotive engines

Either it bent a wrist pin or spun a rod bearing.

Ayuh,... Til ya tear it down, yer really just shootin' in the dark.... It might be repairable....

2) It there a difference in the actual block, rods, crank, etc between marine motors and automotive motors?

Nope,... Not really....

 

[Struc]

Re: marine vs automotive engines

Head gaskets, valves and springs would be fine. No need to do anything there.

Swap out the cam for a marine cam, and make sure to replace the core (freeze) plugs with brass, and you'll be all set (in addition to the things you mentioned above of course).

 

[Maddoxsdaddy]

Re: marine vs automotive engines

Thanks... i've been hearing alot of opinions on both sides of the issue so i figured ask here as well. Get as much information as i can before making my final decision this weekend.

 

[Struc]

Re: marine vs automotive engines

I'm in the process of building up a 4.3l truck engine for my boat right now as well.

http://forums.iboats.com/showthread.php?t=520824

You can save a lot of money by going the automotive/truck engine route. The parts that I sold off from the truck motor I bought already paid for the whole motor cost.

 

[checkmate 219]

Re: marine vs automotive engines

Hey :
I having boosting HP in my 454 for a while - got to have it
Another small item to consider is do you have an enclosed cooling system. If you do your in business with a conversion no problems on block, heads gaskets etc. But if you use raw water for cooling - head gasket, special brass freeze plugs water pump with brass impeller - be sure and don't skimp on starter,distributor, and alternator you must use spark reducing equipment in an enclosed hatch period !!

 

[smokeonthewater]

Re: marine vs automotive engines

I HIGHLY suggest that you pass on the police engine..... many police cars idle for 12 hrs a day or more. and are regularly beat HARD.

I suggest that you simply repair your current engine. If you are doing the work yourself there is no reason it should cost anywhere near $2000... do a compression and a leakdown test on it before pulling it apart.... there may be no reason to do anything with the heads.
inspect and mic the cam/lifters.. they may have MANY years of service left. I have repaired (only replacing parts that were bad) many of my own chevy smallblocks for $50 - $400 depending on the issue at hand..

It is easy to get roped into the "I just want everything new" mindset and spend a bunch of money on things that aren't needed.

example a buddy of mine changed the 60,000 mile 454 in his truck out with a lower mile junkyard engine for something like $1500 because the old one was knocking. I had tried to talk him into fixing the old engine but he flat out refused. He offered to let me have the old engine if I gave him a hand swapping them.... When I got it home and started tearing it down I pulled the valve covers and found that a rocker had broken and the pushrod went through it... I found a couple other rockers cracked so I put new pushrods ans rockers in it along with a performance cam/lifter set and a new timing set and put it in my truck.... I ran that engine HARD without a single issue for quite a few years till I sold the truck.

 

[Maddoxsdaddy]

Re: marine vs automotive engines

There's 2 reasons i'm considering the police motor... Its a vortec w/roller cam and it has only 3500 miles.My current motor is non vortec. I've already dropped the pan on the police motor and taken off the valve covers... everything i've seen so far is spotless. No visible wear on anything.

As for the "marine equipment", i was swapping everything over from my original motor to the police motor including distributor, spark arestor, etc. I will be purchasing a new marine water pump for either motor i end up building.

 

[netting one]

Re: marine vs automotive engines

There's 2 reasons i'm considering the police motor... Its a vortec w/roller cam and it has only 3500 miles.My current motor is non vortec. I've already dropped the pan on the police motor and taken off the valve covers... everything i've seen so far is spotless. No visible wear on anything.

As for the "marine equipment", i was swapping everything over from my original motor to the police motor including distributor, spark arestor, etc. I will be purchasing a new marine water pump for either motor i end up building.

Just my 2 cents, just rebuilt my 1996 5.7 vortec with my engine builder. As we did a complete rebuild i asked alot of questions. The casting materials in a marine are much better, brass freeze plugs, crank and rod tolerances different, heads have different valve seats and valves,camshaft duration and lift- less rpm to match outdrive gear ratios, will it work yes but? will it be correct? my thoughts

 

[Bondo]

Re: marine vs automotive engines

Just my 2 cents, just rebuilt my 1996 5.7 vortec with my engine builder. As we did a complete rebuild i asked alot of questions. The casting materials in a marine are much better, brass freeze plugs, crank and rod tolerances different, heads have different valve seats and valves,camshaft duration and lift- less rpm to match outdrive gear ratios, will it work yes but? will it be correct? my thoughts

Ayuh,... The areas hi-lighted are pure Bull....

There's No differences in the Blocks, nor the Heads, unless specified by a custom builder...
'n there's No differences at all in the metallurgy of the castings...

 

[tpenfield]

Re: marine vs automotive engines

I just tore down and rebuilt my all-original mercruiser 454. It seems to be basically a truck engine with passenger car heads. The head gasket was the type for 'parallel' flow from the block to the heads.

The big things to be sure that you use marine parts for are:

Starter, alternator, fuel pump, carburetor, exhaust. . . these are for fire/explosion safety.

So, sure it will work, and considering your budget constraints, you are not shooting for 'ideal', which would be a marine long block.

 

[netting one]

Re: marine vs automotive engines

I just tore down and rebuilt my all-original mercruiser 454. It seems to be basically a truck engine with passenger car heads. The head gasket was the type for 'parallel' flow from the block to the heads.

The big things to be sure that you use marine parts for are:

Starter, alternator, fuel pump, carburetor, exhaust. . . these are for fire/explosion safety.

So, sure it will work, and considering your budget constraints, you are not shooting for 'ideal', which would be a marine long block.

Not a engine builder at all, i was showing and told this from a guy that is one for 43 years. He told me that the castings were close but changed a little and when we bored it out .030 he said he could always see the difference in the side walls of the marine blocks? I guestioned who put the special marine metal tag on the block too? On my heads we took the old seats out and installed them into a brand new seat of car heads ( i forget the name that he said they were made out of ) not real sure about the valves but we did reuse those also with a valve grind of coarse. Any other old time engine builders out there?

 

[ZachDean]

Re: marine vs automotive engines

The short block will work for you but you won't be able to bolt your intake to the vortec heads. Vortec and throttle body heads or any pre-Vortec head have different intake bolt patterns.

 

[Scott Danforth]

Re: marine vs automotive engines

Little bit of a long story.
I'll start this thread by first saying i'm on a fairly tight $2000 budget and need to rebuild or replace my motor. It's a 1995 5.7 V-8... non-vortec. It was a rebuilt motor when i bought the boat. Either it bent a wrist pin or spun a rod bearing.
With my budget, i still need to replace my trim cylinders and repair serious slop in my gimbal ring.

After doing some pricing, rebuilding will cost be around 2 grand and so will a cheap marine long block. I don't like the idea of getting an engine from a "big box engine builder"... just my .02 cents.

I have come across a 1996 complete (minus intake) vortec motor from a police interceptor with only 3500 miles from a reputable motor builder who had this motor sitting in his garage lookiing for a new home. The motor was pulled at a local dealer for a warranty issue (bad lifter) and replaced with a new motor because the police dept didnt want to deal with tearing the engine apart... yadda yadda yadda. I already have new roller lifters for the motor.

Here are my questions...
1) i've heard... don't put a car motor in a boat. Can i change the head gaskets, valves and springs in the heads, put in a marine cam and be ok? I will still use all my other marine components (carb, distributor, all other accessories)

2) It there a difference in the actual block, pistons, rods, crank, etc between marine motors and automotive motors?

Thanks,
TB

There is NO DIFFERENCE in the block or heads between a marine motor, car motor or truck motor. The cam, head gaskets, and core plugs are marine specific. Boat motors are usually 2-bolt blocks. Truck motors are either 2-bolt or 4-bolt block.

you will need a vortec specific intake (they are cheap, and easily found. I found my dual alloy vortec intake on Ebay, and its an actual volvo-penta part)

If it was me, I would pull your existing motor apart, determine what is wrong, then make the decision. if you decide on the 96 vortec, you will need a marine specific cam. My recommendation would be something along this line http://www.summitracing.com/parts/CCA-K08-416-8/

 

[Maddoxsdaddy]

Re: marine vs automotive engines

The short block will work for you but you won't be able to bolt your intake to the vortec heads. Vortec and throttle body heads or any pre-Vortec head have different intake bolt patterns.

I've noticed. Its a shame GM had to switch things between '95 and '96. I'm looking for a simple aluminum intake at this point. I don't want anything too fancy. I was thinking a Weiland or an Edelbrock performer would be sufficient.

I'm getting a 350 Mag Roller cam specifically for 350 Mag engines. What head work will i need to do if any? Stainless valves and better springs?

 

[Bondo]

Re: marine vs automotive engines

I've noticed. Its a shame GM had to switch things between '95 and '96. I'm looking for a simple aluminum intake at this point. I don't want anything too fancy. I was thinking a Weiland or an Edelbrock performer would be sufficient.

I'm getting a 350 Mag Roller cam specifically for 350 Mag engines. What head work will i need to do if any? Stainless valves and better springs?

Ayuh,.... A Shame,..?? The Vortec Heads are the single Greatest improvement to the SBC, since 1955....

So long as yer new cam is under .500 lift, the heads will be just Fine...

 

[smokeonthewater]

Re: marine vs automotive engines

an aluminum intake is not recommended unless you have closed cooling due to accelerated corrosion.

 

[Maddoxsdaddy]

Re: marine vs automotive engines

Ayuh,.... A Shame,..?? The Vortec Heads are the single Greatest improvement to the SBC, since 1955....

So long as yer new cam is under .500 lift, the heads will be just Fine...

I was meaning why did they switch between those 2 years in particular... I'm glad they did switch to the vortecs...
That's good to know about the heads... Less $$$ i have to spend. Seeing as there are only 3500 miles on them, i don't forsee any issues.

Man i'm looking forward to getting this done.

 

[Scott Danforth]

Re: marine vs automotive engines

Ayuh,.... A Shame,..?? The Vortec Heads are the single Greatest improvement to the SBC, since 1955....

So long as yer new cam is under .500 lift, the heads will be just Fine...

with minimal work you can go much bigger on cam.... however for a boat, there is no need to go above .500 lift.