Merc OM 606 suitable for Scarab project?

[R400]

A friend of mine has bought a Wellcraft Scarab 29 and intends to marinise a Merc OM 606 out of an E300 turbo and mate it to a Bravo 3 leg.
Question , has anyone used or come across this power unit . It’s an ambitious project I know but he’s a gifted mechanic but any tips would be gratefully received. The boat originally had twin petrols but the last owner but one fitted a single diesel, Toyota 4.2 in some incarnation. I’ve looked around the hull and deck and must say I’m impressed with the quality of the build, very strong though a bit Miami Vice in appearance . If he ever gets it going you’ll certainly see him coming.
Good Christmas to all

 

[QBhoy]

There may or most certainly will be some issues with this...at the risk of sounding negative;

Apart from the cardinal sin of putting a diesel in a Scarab, haha, I’ll try and lost why

The common problem many face, when replacing the usual GM small or big block V8 with a diesel is usually to do with the Drive ratio and gearing. Many wrongly assume (despite being mechanically gifted) that one can simply remove a 250-300hp V8 petrol and just cleverly engineer and fit in a similar HP Diesel engine. This usually isn’t the case.
This is down to a few key factors. The power curve and delivery characteristics are so different between a petrol and a diesel. The peak power at certain RPMs differ too. The max rpm available also differ.
This usually means that a change of Drive ratio is required. Some are lucky and get away with a change in prop pitch, but most need to change the ratio and prop...often resulting in a serious drop in performance, but more worryingly, a financial outlay that far outweighs the benefit of the diesel in the first place. Not only that, if the financial investment is thrown at it, you will never claw it back when time to sell.
Apart from all of the above, a Scarab is a high performance boat that deserves a high performance engine. To get the equivelant power output from a diesel would mean a seriously expensive package. In my opinion, she will just never be quite right with the diesels. Then finally, that lovely straight through V8 Gm petrol exhaust note is gone forever.
On the other hand, I respect the engineering behind it, but the Drive ratio is key to it all.
A final thought and to summarise;
The original 350-496ci (5.7-7.4l) V8 would likely produce peak power between 4400-4800 rpm or similar. The replacement diesels (without looking it up) would likely produce peak power much lower in the Rev range and may even not be capable of even reaching the 4800 rpm the original Drive ratio was intended for.

 

[alb40]

Whilst it could probably be done, an OM606 isnt all that powerful and It would probably be a waste of money for disappointing performance.

 

[matticraig]

hi
I have a sunseeker tomahawk 37 I have replaced the petrol 454magnum engines with Mercedes om606 diesels I run the original bravo drives with the original gearing and props the sunseeker is 7 tonne and made 28kts with the engines in standard tune . I have upgraded the pumps with 7.5mm element dieselmeken tuned pumps and bigger turbos I have only test run with one tuned engine and one standard so far but made 40kts so should make 50 with both (they are tuned to make 350hp) , he will need to make a bell housing conversion plate and a flywheel ,and use the bell housing and drive connector from the petrol ,fabricate some rear engine mounts (keep the original front mounts from the bellhousing) and make sure you have enough cooling ! .good luck.. ps I think a scarab should have at least 2 ...

 

[matticraig]

The om606 has a similar power curve to petrol engines with a top end of 5500rpm ,they are 200kg lighter than the 454petrol and with bolt on parts will make over 500hp..they run 350hp reliable hp as fitted in my boat with tuning parts costing £1100 .gearbox and props are standard.(I experimented with different props before tuning engines and found no significant improvements)

 

[Bradbertram25]

The om606 has a similar power curve to petrol engines with a top end of 5500rpm ,they are 200kg lighter than the 454petrol and with bolt on parts will make over 500hp..they run 350hp reliable hp as fitted in my boat with tuning parts costing £1100 .gearbox and props are standard.(I experimented with different props before tuning engines and found no significant improvements)

I’m very interested Matti!

I have a 25’ Bertram sedan and have been in contact with Dieselmeken in regards to the pump element upgrade.

My boat weighs 2.5T do you think a single OM606 repower with pump work will push it along over 30knots?!

Also what about cooling on the OM606? What set up are you running? Closed circuit? Turbo cooling somehow?

Do you have any videos of yours running?

Would appreciate any help!