Renovation OM 606
Renovation OM 606
I have a 4500lb RIB with a cummins 6bt, non-intercooled. With an 18" prop, I could not get it to target rpm. Shifting to a 17" solved all my problems, due to increased slip allowing the motor to run at full rpm.
You can find slip calculators on the internet. Boatdiesel has one also. Boatdiesel is worth the small subscription price. There are some very experienced people there on the forums who can help you think your problems through.
If that exhaust manifold is stainless, I salute your welder. But I also agree that what you want is a water jacketed turbo, instead of a water jacketed exhaust manifold. That way the turbine sees the full exhaust temp and energy, before dumping gas into a water jacketed elbow, then out the wet exhaust. So your seawater runs through a water to water heat exchanger to cool the internal motor cooling loop, then dumps its water into the exhaust elbow.
atypicalguy
02-06-2019, 04:44 AM #21An easy thing to try would be a smaller diameter prop. By increasing the propeller "slip" (difference btw theoretical speed from prop rpm/pitch and the actual speed of the boat) you can get the motor into higher rpm and onto boost. This needs to be done for your typical running condition, so the weight of the boat fully loaded for worst case scenario. Essentially, you are looking for gearing (transmission and prop) that allows the motor to achieve full target rpm when fully loaded. This avoids "lugging" the motor and killing it prematurely.
I have a 4500lb RIB with a cummins 6bt, non-intercooled. With an 18" prop, I could not get it to target rpm. Shifting to a 17" solved all my problems, due to increased slip allowing the motor to run at full rpm.
You can find slip calculators on the internet. Boatdiesel has one also. Boatdiesel is worth the small subscription price. There are some very experienced people there on the forums who can help you think your problems through.
If that exhaust manifold is stainless, I salute your welder. But I also agree that what you want is a water jacketed turbo, instead of a water jacketed exhaust manifold. That way the turbine sees the full exhaust temp and energy, before dumping gas into a water jacketed elbow, then out the wet exhaust. So your seawater runs through a water to water heat exchanger to cool the internal motor cooling loop, then dumps its water into the exhaust elbow.
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