what's a marine engine?

[longbedrick]

what makes a "marine" engine different than a regular block?

[old Rusty C10]

marine engines are made for the boat car engines are made for the car...some marine engines turn the opposite way of an automotive engine if memory serves correct

[3r!c84]

yes.my buddy truck has a marine engine.that spins backwords

[cableguy0]

The main difference is the camshaft. freeze plugs are brass. water pump impellor is brass. there are minimal differences. as stated some are reverse rotation which you wouldnt want.The cam used in most boat engines is a terrible cam for a street cam mainly due to operating range but its not a deal breaker.

[dooce]

Originally Posted by 3r!c84

yes.my buddy truck has a marine engine.that spins backwords

Can someone explain how this would work?

[cableguy0]

Originally Posted by dooce

Can someone explain how this would work?

It wont.... the 3 forward gears would become reverse gears. its not possible

[3r!c84]

you gotta drive in reverse lol nah he just fliped the axel over so it would run backword (im not 100% sure,i forgot what he said he did)

[Chlsnk]

Also the flexplate is different.

[80SPORT]

The Chevrolet marine engines are very similar to the pre emission truck engines....and the GM Performance parts engines.We are a Mercury dealer and have installed marine engines in Camaros and pickups with excellent results.One advantage of the marine EFI is that it is stand alone ....no oxygen or speed sensors to hook up.

As mentioned elsewhere the marine engine comes with brass components in the cooling system;for this reason we do not suggest using automotive engines in boats that will see salt water.

The reverse rotation motors were used in some direct drive ski boats and one side on twin engine direct drives;they were discontinued in 87 when the 1 piece rear main seal came in.

[Big Port Jimmy 6]

Cams are different and the firing order is backwards. The starter and flexplate are made to work backwards. I would assume that the dist gear is also different. Jay

[454HO]

Originally Posted by cableguy0

The cam used in most boat engines is a terrible cam for a street cam mainly due to operating range but its not a deal breaker.

I'v known lots of people that ran a marine cam in a street car. I myself have a marine cam in my L-29 Vortec big block motor. There is nothing terrible about it. It is much better than the factory cam that came in the engine, and it is a true billet roller cam. Likewise, there are lots of marine engines out on the waters that run so called street cams.

The issue with cam timing in a marine application is the exhaust valve closing event. You want to make sure the exhaust valve is fully closed before the piston goes too far down on the intake stroke (ie little overlap). Otherwise, it can suck water in from the exhaust. This is reversion, and if you are not carefull with cam selection you may end up hydro-locking the engine. Other than this, and the above mentioned reverse rotation engines, there is nothing unique about cams used in marine applications.

Cam lift, duration, lobe seperation, etc are all spec'd with the intended operational parameters of the engine. Marine engines need a lot of low end torque to get the boat moving and up on plane. And they typically have cruise rpm range much higher than an automobile engine. Therefore factory marine spec cams typically have a wider LSA to get a broader torque curve. But again, there is nothing terrible about that for street use. In fact, it is very similar to the popular RV cam grinds.

[SSC's76]

Theres nothing magic about making an engine spin backwards it just requires a cam gound in reverse or installed 180* out an oil pump with reverse gear set and means to kick the engine over in the oposite direction. As long as you have a mount point for the starter, replace the oil pump and cam a reverse rotation engine is no different.

[turbo350]

The 305 in my boat is not very different than an automotive 305 of the same year. Its rated at 225 hp which is a bit more than the automotive 305s of that year. Big difference is the cam of course which is similar to an RV grind. Not sure on the heads, I'd have too look at the numbers again but this is a '78 so its likely smog style heads. Boat engines work twice as hard as a car engine so they need the power down low. The only other real difference on mine are the marine grade head gaskets and the marine grade starter. I run an automotive Holley carb. This engine if put in my truck would run just fine.

[2bits]

I put a Mercruiser 250 Inline 6 in my '71 truck, it spun the "correct" way and ran great with good low end torque and just fine on the freeway. Same block, just built better, just make sure it's one that turns the right way

[78-5.3]

arent most reverse rotation engine fitted to boats with 2 engines to stop the boat from wanting to go in circles and pull straight????

[3r!c84]

Yes... they are also some Honda motors that are reverse rotation motors

[LONGHAIR]

Originally Posted by 78-5.3

arent most reverse rotation engine fitted to boats with 2 engines to stop the boat from wanting to go in circles and pull straight????

It's not about "going in circles", it's about efficiency.
With 2 props running the same direction, and placed side-by-side, the water that "exits" the props "fights" with itself. So there isa bunch of thrashing but no thrust...
With counter-rotating props, the water is moving together and in the same direction.

[4x4toy]

If you convert a reverse rotation marine engine to standard rotation engine you will need to change-
camshaft,distributor,oil pump,starter motor,rear main/front crank seals,(yes these are different) and flywheel.

[McMurray76]

The BBC in my boat does run "backwards", the top half (cam, distributor, oil pump) runs forward though. This is done with a special cam and timing set. Instead of a timing chain on two gears the gear on the cam meshes directly with the gear on the crank reversing the direction of rotation. This could be easily modified to run in a standard rotational direction. Hope I helped and not hindered.

[87Bob]

With a reverse rotating engine. OH just think of the fun you could have. What a wild mid engine off road buggy/sand drag buggy /mud bog buggy you could build. Perfect weight balanced! YEEEEEHAAAAA!!!