351 Marine engine

[John Marinan]

I've come across a 351 engine in a 96 Mastercraft. It's a PCM marinized engine. It's being called a GT40 EFI engine. Do any of you know if there's anything special about this engine?

 

[AZ69EB]

Yes. It should have the GT40 lower iron intake that can be bolted to the GT40 tubular upper or Explorer upper. The lower intake should be worth about $350 and up depending where you live or how bad someone wants it.

 

[Broncobowsher]

It better still have the intake on it. That is the cast iron version of the GT40 lower.
The engine itself isn't that special. Typically you will find a few little things like brass freeze plugs and the head gasket will have a different fire ring that won't rot out in salt water. The EFI will be marine specific, don't think you will be adapting that. But the engine itself should be a standard 351W.

 

[SteveL]

Nice find with that intake depending on the price.

 

[Mike Bryan]

Check rotation, some are reverse rotation to counter prop torque. The starter will be different. My Ski Nautique has a reverse rotation 351 in it. The good thing about marine engines is that the bore taper is genually very straight because of the clean operating environment.

 

[spap]

Would probably have to re-cam the engine, marine are set up to run at full throttle. Marine engines might have forge internals too, but they live a hard life.
Also check for corrosion if you live near any salt water good find

 

[John Marinan]

Thanks for the replies. I actually would have to buy the whole boat. The trailer is good, the hull is fair. The trans is good. Parting it out for the engine would probably be more trouble than it's worth. I was actually hoping it was a reverse rotation as I have boat that could use it, and even a rebuilder is tough to find. Marine engines usually have forged internals, lower valve spring pressure and a few other things. Ford reverses the crank and the cam, chevy uses a gear to gear combo instead of a timing chain, this retains a standard cam rotation. Would this 351 likely be a roller cam engine?

 

[sykanr0ng]

Would this 351 likely be a roller cam engine?

If the block is '94+ it will be a roller block, but that does not mean it will always have a roller cam.

 

[Broncobowsher]

Check rotation, some are reverse rotation to counter prop torque. The starter will be different. My Ski Nautique has a reverse rotation 351 in it. The good thing about marine engines is that the bore taper is genually very straight because of the clean operating environment.

Not in this era. Transmission technology has improved enough that the counter-rotation is now done in the transmission not the engine.

As for the cam, generally a good choice. The original 5.0 HO was nothing more than the marine cam put into a car. My old HR manager was there for the discussion when Ford engineering was looking to make the HO and (I forget his name) pulled the marine cam out and handed it to them and said that is what they are looking for. He was right.

But having to buy the whole boat to get the engine makes it an issue.

 

[John Marinan]

Not in this era. Transmission technology has improved enough that the counter-rotation is now done in the transmission not the engine.

As for the cam, generally a good choice. The original 5.0 HO was nothing more than the marine cam put into a car. My old HR manager was there for the discussion when Ford engineering was looking to make the HO and (I forget his name) pulled the marine cam out and handed it to them and said that is what they are looking for. He was right.

But having to buy the whole boat to get the engine makes it an issue.

I'm not familiar with any ski boat transmissions that convert the directional torque to the opposite rotation. Do you know who makes them?

 

[Broncobowsher]

Not needed for a ski boat. Only twin engine configurations need counter-rotating screws. So that is the only place you will find them. Not in a single engine ski boat. Too easy just to order a screw that is the correct rotation.

 

[bmc69]

I'm not familiar with any ski boat transmissions that convert the directional torque to the opposite rotation. Do you know who makes them?

I'm not either...not until you get well in to the larger marine gears from folks like ZF and Twin Disc,

Outdrives, on the other hand, are pretty much now all designed for either rotation direction. The Volvos always were, but their patents locked others out. Now that protection has expired and The Bravos from Mercury, for example, use the bi-direction design of the upper gearbox similar to Volvo's.

"Wrong hand" marine engines for smaller vessels are pretty much a thing of the past.

And another nit picking point...not nearly as many marine engines used forged cranks as the myths would have you believe. In the case of the Ford marine engines, the 427s are the only ones I'm certain had steel cranks.

 

[John Marinan]

Reverse rotation was used to balance the smaller, lighter boats for driver position. Now inboard boats have become big heavy tug boats, so no need for any drivers side lift. The 427 is a much sought after marine engine, they're considered to be one of the best, and strongest ever made.

 

[BanditBronco]

I have an 80's marine 351 block in my truck. You guys got me all excited when you said forged internals... either way my foot still weighs the same. The only thing I noticed that was different is a lot more calcification in the coolant passages, pretty nasty what was in there.