gm marine vs regular engine?

[bandit86]

in 87 a tpi 350 camaro made 220 hp yet my carburated 350 boat engine made 260 hp. was the difference in better heads or cam?

what would be the disadvantage of putting a boat engine in a car? is it any heavier?

 

[JustJason]

Re: gm marine vs regular engine?

different cam..... no emissions.... where HP is actually measured from...... RPM range.....

what would be the disadvantage of putting a boat engine in a car?

in a drag and drop scenario...... the engine would have very little perciveable power below 2k rpm, then it would take off like a rocket. not very good for torque converters and clutches...

 

[Uraijit]

Re: gm marine vs regular engine?

in 87 a tpi 350 camaro made 220 hp yet my carburated 350 boat engine made 260 hp. was the difference in better heads or cam?

what would be the disadvantage of putting a boat engine in a car? is it any heavier?

The block and heads are exactly the same. The main differences are head gaskets MUST be composite on a boat engine, and the freeze plugs are brass. As far as the power, that's all decided by the cam.

If you put a car cam in your marine engine, it would work great in your car.

Put a marine cam in your car engine, and change freeze plugs and head gaskets, and you now have a marine engine.

 

[bandit86]

Re: gm marine vs regular engine?

I assumed marine engines were usually 4 bolt mains to stand up to continous high speed usage

was there such a thing as a 400 chev marine engine?

I'm looking at an older camaro and I was thinking that a marine engine would be more durable

 

[Uraijit]

Re: gm marine vs regular engine?

The primary difference between a 4-bolt and 2-bolt main engine is the number of bolts.

a 4-bolt main is not going to make your engine any more suited to marine use.

 

[mylesm260]

Re: gm marine vs regular engine?

In the old days, marine motors used to be a lot different, Having recently researched this, GM marine and GM automotive engines generally have the same internals, and the same cams.

The reason you see such a big difference in power is the exhaust systems.

In a car, your pushing the exhaust gas through 10 feet of pipe, a resonator, two catylitic converters and a mufler.

In a boat, the exhaust is actually sucked out by the venturi effect of the boat going forward in the water.

 

[Uraijit]

Re: gm marine vs regular engine?

Cams are NOT similar between car engines and boat engines. They are very similar between Truck, Marine, and RV engines, however.

If you're taking an engine out of a CAR, replace the cam. If it comes out of a truck, it's usually fine.

 

[Maclin]

Re: gm marine vs regular engine?

I think the original poster was wanting to put a boat engine in his car to get a power boost.

The biggest difference between the car's 220hp engine and the boat's 260hp engine is how (and "where") they are measured. The actual output is close, in fact the car engine may make more power up in the higher rpm ranges.

As far as putting a 260hp Merc engine in your GM car, the boat engine would have good low end and mid range but not as much higher rpm range. Overall I would not expect much difference in the car's performance.

There are more things you could do to the car's current engine that could surpass what you could get with just swapping in a boat engine.

 

[Bondo]

Re: gm marine vs regular engine?

There are more things you could do to the car's current engine that could surpass what you could get with just swapping in a boat engine.

Ayuh,..... Exactly.....

 

[Mkos1980]

Re: gm marine vs regular engine?

I've got 2 350 TPI Thirdgens and one , which is stock, put down 231RWHP and 331 RWTQ to the wheels, which means they are alot more at the fly.

 

[hbhobby]

Re: gm marine vs regular engine?

I have a question about going from a car to a boat. I have a 93 baja and just melted down the 454 that was in it and don't really have the cash right now to replace with same motor. I have a 69 vette 427 motor freshly rebuilt. What, if any, is the problem of putting in the 427 verses the marine 454? I'm not concerend about CID because the 427 has more ponies than the 454 did. I talked to a boat shop (who just happened to have a 454 mag ready to sell me) and they said it would not work at all. but most everyone else I have talked to said it should work? I am very confused and am new to these types of boats. any help would be appreciated!

 

[mkast]

Re: gm marine vs regular engine?

What peak RPM does the 427 turn?
What was the peak RPM the 454 turned?
Boats need to make HP at a lower RPM so the prop can use it.
Anything over 5000 RPM is pretty useless in a boat.

 

[erikgreen]

Re: gm marine vs regular engine?

Yeah, don't compare the HP without looking at the RPM and torque.

 

[hbhobby]

Re: gm marine vs regular engine?

it is bacically a stock 427 that revs out at about 5000-5500 rpm. My 454 would rap out at 4500 rpm with a full boat. My concern is mainly the manifolds bolting up and the coupling bolting up easilly or will I need a lot of modifications? I did talk to another boat shop and they said everyting should work fine, but I do know that a 427 uses a different flexplate ot flywheel than a 454 does?

 

[hard-3]

Re: gm marine vs regular engine?

I think you will find that how the power ratings are measured will be the difference from marine to automotive engines. years ago the advertised horsepower was calculated differently than S.A.E. ratings are today. Alot of the horsepower ratings are averages not actual horsepower measured at the flywheel on a dyno. I am not sure if the marine engines are flywheel hp or if they are measured at the prop shaft just because it says 260 hp on the tag does not mean you are getting the actual work of it at the rpm range that you need it to. as stated in previous posts the cam determines where in the rpm range that it produces the power . if you use a cam that makes its hp/torque in a power range that you are not wishing to operate in ,it will not produce the desired result. example power range 4500-7000 rpm if peak torque and hp does not come in until above 4500 rpm you are maxed out on the drives before the power comes on. or --- cam designed for torque under 3500 rpm most rv grinds are in this range hp and torque requirments are above the range that produces the most available power check with the cam grinders and see if the camshaft you have is in the rpm range that you want to be most can tell you what oem cam profile you have by the part number and can suggest a cam profile for what you want. You might also find that an automotive engine may not have all of the mounting bosses drilled and tapped for the accessories you need on the marine engine application. late model GM engines also came with both metric and sae threaded holes. also Gm small block 400's had 2 bolt mains and are notorious for cracked blocks in the cylinder area because of thinnenss between the cylinders.

 

[stinger222]

Re: gm marine vs regular engine?

Don't you dare put that 69 427 in a boat Not that it won't work, but that engine is very valuable to a corvette enthusiast who is looking to restore a 69 vette....You can put any run of the mill 454 truck motor in your boat, don't waste that engine in your boat. The 454 does have more tq down low, which the boat appreciates...

 

[bruceb58]

Re: gm marine vs regular engine?

If you measured the HP at the output of the engine, the two engines will likely measure the same HP. The difference is that boats are measured at the prop and autos are normally measured at the axle.

 

[Bunk]

Re: gm marine vs regular engine?

Everything that bolts to a 454 should bolt to a 427. The 454 and the 427 use the same block. They both have the same bore size. The difference is in the crankshaft. The 454 has a longer stroke. Intake manifolds, water pumps, heads, exhaust manifolds, etc are all interchangeable. The only problem you should have is that the 454 is external balanced and the 427 is internal balanced and so the flywheel and harmonic balancer are not interchangeable. Put a 454 flywheel on a 427 and you will shake the whole thing to peices. The 427 will rev better, but the 454 will have more torq with all things the same. With all this said, I am with a previous writer, don't waste the 427 on a boat. Sell the Vette 427 and buy a 454 and a spare.

 

[mthieme]

Re: gm marine vs regular engine?

For what it's worth...a friend and I love to get old jet boats and blow them up! One summer we went through four 455 Olds motors...the junkyard ran out of 'em. We had the boat broken by then anyway. We got to the point where it took only one hour to swap the motor. We're playing with another one now. It has a 454 chevy that seems to be a little harder to blow up. Since it lasted a whole season, we're seeing signs of water in the last cylinder, had to put on four starters since one time under water trashes a car starter.
But how else can you go 90 mph on the water so cheap?