A company called Peninsular marinized the GM 6.5 diesel. Not the most stalwart engine to start with and they found out that the factory 21 to 1 CR caused the pistons to start scuffing/galling the bores after 24 hrs. of continuous operation at 80% load. They reduced the CR to 18 to 1 by having AM General build their pistons with the pin location slightly higher. This was a simple way to lower compression and it seems to have worked as they report no further issues after this change. They also use a large non-wastegated turbo in the marine applications. The street turbo is designed for low end torque not high rpm continuous duty.

Given that the 617 is also a 21 to 1 engine it would seem reasonable that the same issues may be possible in the same type of scenario. A slight drop in CR may enhance longevity in long duration at relatively high power settings.

Since a boat has almost unlimited cooling capacity it would also seem prudent to use large water intercoolers. Its just pumps and plumbing, right? A larger turbo would probably be another reasonable change for the same reasons stated above. I don't see how either could hurt and likely would help.

That said, the installation and fabrication appear first rate. If its all DIY the man is quite talented.

RT

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