Hi All,
Any thoughts or advice would be appreciated.
My 175 has a 3.0 Mercruiser with Alpha One sterndrive (all standard for the 2003 model), when using a Piranaha 4 blade composite prop with 18" pitch the WOT is 4800 rpm with a GPS speed of 28kn, the WOT range for the engine is 4400-4800 and this is the fastest its ever run with the 18" prop.
if I swap the blades to make it a 20" pitch the WOT only gets to 4000 with a GPS speed of 29kn which is less than it was a few months ago, back then I would get about 34kn GPS speed with WOT of 4500 rpm.
The boat load hasn't changed and performance seems abaout the same as it was with the 18" prop but with the 20" there has been a noticable reduction in top end performance. I'm thinking that it may be an engine power issue and I've removed the fuel filter from the standard fuel pump and put a high flow filter with water bowl inline instead (on the pump suction side, close to the tank) but this has made no difference.
The spark plug colour looks OK so I think that the fuel/air mixture is good but I'm not sure what to check next.
Any thoughts or advice would be appreciated.
My 175 has a 3.0 Mercruiser with Alpha One sterndrive (all standard for the 2003 model), when using a Piranaha 4 blade composite prop with 18" pitch the WOT is 4800 rpm with a GPS speed of 28kn, the WOT range for the engine is 4400-4800 and this is the fastest its ever run with the 18" prop.
if I swap the blades to make it a 20" pitch the WOT only gets to 4000 with a GPS speed of 29kn which is less than it was a few months ago, back then I would get about 34kn GPS speed with WOT of 4500 rpm.
The boat load hasn't changed and performance seems abaout the same as it was with the 18" prop but with the 20" there has been a noticable reduction in top end performance. I'm thinking that it may be an engine power issue and I've removed the fuel filter from the standard fuel pump and put a high flow filter with water bowl inline instead (on the pump suction side, close to the tank) but this has made no difference.
The spark plug colour looks OK so I think that the fuel/air mixture is good but I'm not sure what to check next.
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