Volvo 5.7GL to MerCruiser 357 Plus-Series

[mistermark]

First post, here we go!

We have a 1997 26' Cruiser with a 5.7GL Volvo (twin prop) (215HP) that has blown with 282 hours on it. It was overpitched and only tach'd 4000 rpm at WOT, so it's done. I will not get it rebuilt (no one capable in my area) and don't want to long-block it as the boat just doesn't have the power we'd like. If we go with a new MerCruiser 357 Gen+ (325HP) and use my old flywheel, flywheel housing, starter and exhaust system (freshwater, recently changed), will this work? The guys that take care of it are excellent and are 35+ years experienced...The boat has the round cannon plug on the engine, so we don't have to worry about gauges I believe, and with the Bravo, we won't have to worry about the shift interrupt. Does this make sense to anyone?

 

[bruceb58]

Re: Volvo 5.7GL to MerCruiser 357 Plus-Series

You are just doing a block switch right? Not sure why you mention Bravo.

Not sure what comes with the engine. You will have to use your Volvo manifolds.

Hope you realize that the HP specs of the 2 engines are different specs. Your Volvo was spec'd at the prop and the Merc is at the crankshaft. I doubt the power will be much different unless your original engine didn't have Vortec heads. Probably likely it didn't.

 

[jerryjerry05]

Re: Volvo 5.7GL to MerCruiser 357 Plus-Series

Fill out the profile and locationThis is from a friend who has a lot of experience.
(There is no way in h e l l that this MerCruiser 357 Gen+ engine offers a usable 325 hp at an RPM that is also usable for Marine cruiser use. It's likely been rated @ 5,200 rpm or so.

I'd stay with the Volvo Penta Duo Prop drive, and do a SBC 6.3L (383 cu in) with an alternate build. Michigan Motors can do this build for him.)
Sent U a PM

 

[Summer Fun]

Re: Volvo 5.7GL to MerCruiser 357 Plus-Series

This is from a friend who has a lot of experience.
(There is no way in h e l l that this MerCruiser 357 Gen+ engine offers a usable 325 hp at an RPM that is also usable for Marine cruiser use. It's likely been rated @ 5,200 rpm or so.

I'd stay with the Volvo Penta Duo Prop drive, and do a SBC 6.3L (383 cu in) with an alternate build. Michigan Motors can do this build for him.)

Let me take a guess on who that is.........

RetardoMarine from M.E.... Right. :facepalm:

 

[mistermark]

Re: Volvo 5.7GL to MerCruiser 357 Plus-Series

More details...

The engine we want to drop in is a 357 Gen+ 4V 4bbl engine that rates at 325 HP. The Alpha spec engine rates at 275 HP. These are MerCruiser engines that have a 3 year warranty. Besides exhaust and flywheel/coupler exchanging, it will work in the boat. The power trim runs through a relay on the stbd side exhaust elbow that I'm using, and it has the round cannon plug so the boat is compatible with the engine harness. Spoke with the guys at Marine Parts Express yesterday who told me they wouldn't sell me a Volvo complete before they sold me a MerCruiser, mainly because the Volvo is twice the money.

Michigan Motors...have seen three boat owners go this route on our lake and they all had their own set of issues. Realistically I'll only be picking up another 75 HP or so at the crank, all of which the drive can handle. With this power increase, I shouldn't have to get the props bent either as its over pitched with the old 5.7 GL.

 

[bruceb58]

Re: Volvo 5.7GL to MerCruiser 357 Plus-Series

Does your previous engine have Vortec heads?

 

[mistermark]

Re: Volvo 5.7GL to MerCruiser 357 Plus-Series

I'm unsure. It's a 5.7GL PLKR.

 

[bruceb58]

Re: Volvo 5.7GL to MerCruiser 357 Plus-Series

I'm unsure. It's a 5.7GL PLKR.

Your current engine does not have Vortec heads. You will get 50 to 60HP increase from that upgrade which makes sense.