7.4 GI PWTR won't go over 3100 rpm

Simon in Muscat

Recruit
Joined
Dec 10, 2011
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1
I have a 1999 Volvo Penta 7.4 GI PWTR in a Chris Craft Concept 27', with a stainless steel F7 duoprop the maximum RPM at WOT was 3100 rpm, I've recently fitted an Aluminium D2 duoprop and I'm getting to 3100 rpm at around 75% throttle, after which the engine is cutting out. I understand this engine should do between 4200-4600 rpm, so clearly there is a problem. Unfortunately I live in a part of the World where there are not a lot of good marine mechanics with Volvo Penta experience and the Volvo Penta people don't have too much experience with Gasoline engines. I've been told to check the fuel pump pressure, however, someone else has said that if the engine is getting to 3100 rpm then the problem is not the fuel pump. I've also been told it's quite likely to be a faulty sensor that's causing this and to use a diagnostic tool to identify the problem - unfortunately the engineer sent to investigate this could not locate the 10-way DLC, which I believe should be at the starboard front of engine. Any good advice would be very welcome.
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 7.4 GI PWTR won't go over 3100 rpm

You have engine problems, not prop problems. If it was working OK with a set of props and then dropped rpm, you can't blame that on props.

You can download the manuals for your engine HERE You need to do the basics first, tuneup, compression check, checking the fuel filters for water etc.
 
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