Penta 280 outdrive to mercedes om648

[wanderer7]

Hi all. New on here and wondering if someone wouldn't mind sharing some knowledge with me. I bought an old fairline mirage 29 with twin aq130 engines coupled to penta 280 outdrives. Love the boat, hate the engines. I have it in my mind to convert to a 6 cylinder mercedes diesel engine. Specifically the om648. There is an adaptor kit available to convert to old style (th400, power glide etc,) chevy gearbox. I have been looking at penta gm flywheel covers (bellhousings.) But there seem to be multiple styles. Any advice as to what flywheel cover would fit the 280 leg and likely to have the correct era of bolt pattern? Thanks in advance.

 

[Scott Danforth]

Are there marine exhaust manifolds for the old Mercedes. If not, consider a different motor. Water cooled exhaust and turbos are a must

You will need to change the gearing in the drive for a diesel.

The AQ130 are Volvo motors. Switching to a GM pattern is a different PDS housing

 

[matt167]

Marine manifolds for that engine doesn’t exist unless you find something in some corner of Europe/Germany. You can’t safely run dry exhaust. That is your first hurdle. Mercedes diesels are great though.

 

[wanderer7]

Are there marine exhaust manifolds for the old Mercedes. If not, consider a different motor. Water cooled exhaust and turbos are a must

You will need to change the gearing in the drive for a diesel.

The AQ130 are Volvo motors. Switching to a GM pattern is a different PDS housing

Thank you for the reply. There is no off the shelf manifold but I can fabricate one. In my mind the drive adaptor is more difficult. Yes I will need to change the flywheel cover (primary drive shaft housing.) That was my question, will the double bearing pds work with my outdrives, also which size would I need for that era gearbox?

 

[wanderer7]

Marine manifolds for that engine doesn’t exist unless you find something in some corner of Europe/Germany. You can’t safely run dry exhaust. That is your first hurdle. Mercedes diesels are great though.

Thank you for the reply. There will many hurdles along the way . To me being able to marry the engine and outdrive is the first hurdle to clear.

 

[wanderer7]

Are there marine exhaust manifolds for the old Mercedes. If not, consider a different motor. Water cooled exhaust and turbos are a must

You will need to change the gearing in the drive for a diesel.

The AQ130 are Volvo motors. Switching to a GM pattern is a different PDS housing

The aq130 has a wot around 5000 rpm. The om648 has a red line at 4500 max power at 4200. Can the correct drive be achieved by re-propping the existing drive? I'm not really intending to use the full power of the om648, the hull is designed to cruise using around 180 hp total.

 

[Scott Danforth]

Thank you for the reply. There will many hurdles along the way . To me being able to marry the engine and outdrive is the first hurdle to clear.

bolting the two together is the least of your issues. getting a GM V8 PDS housing for a 280 and the adapter you mentioned.... just money and wrenching

the water cooled marine manifold and turbo housing is the hurdle that you need to clear first.

the last water cooled one-off manifold that I designed for use in mining equipment on a Cummins QSB3.3 cost about $15,000. yes, that is $15k.

it was 3 pieces of billet steel that were CNC machined, then tig welded together, then x-rayed and pressure tested, then post weld machined. to get to that price, we had to order 10 of them.

Marine and mining both have a maximum temperature of 200F / 93C to keep things from burning.

that is the exhaust manifold surface and the turbo surface.

It would be cheaper to get two of the marinized VW inline diesels and bolt them in and hop up the fueling

 

[matt167]

Thank you for the reply. There will many hurdles along the way . To me being able to marry the engine and outdrive is the first hurdle to clear.

As Scott said. Hooking it up with an available adapter is just nuts and bolts. But you cannot run a dry exhaust.

Figure out your cost to marinize the engine with wet exhaust. Keep in mind that production manifolds start at $1k in general

 

[Scott Danforth]

5-cylinder VW 2.5 liter marine diesels are rated at 165hp. to get to 180, very slight boost in fueling is needed. most of the available electronic tweeks push it over 200hp

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