4.3 Volvo Penta won't start in the water

[DylanDuluth]

I can turn it on in the driveway and idle for hours. I can rev up in RPM mode. When I get in the water it won't start unless I am in RPM mode and give it some throttle. It dies when I back down to neutral. Over and over again. When I got it back to the driveway this time the left riser was very hot when I ran it. Super confused.

 

[ThomW]

I can turn it on in the driveway and idle for hours. I can rev up in RPM mode. When I get in the water it won't start unless I am in RPM mode and give it some throttle. It dies when I back down to neutral. Over and over again. When I got it back to the driveway this time the left riser was very hot when I ran it. Super confused.

Sounds like the idle may need to be adjusted. When you are in the water, what are the RPM's when it stalls? sub 800? Idle adjustment can only really be done properly in the water with the back pressure that being in the water creates. Start it in the water, let it warm up, then try and get back to neutral. If it starts to die out or RPM's get too low...raise the idle a little. Obviously, don't set the idle above recommended specs, if it won't idle at the proper RPM's, its another issue.
Riser temp may be a rust flake or something else blocking a passage. Probably not related to the idle issue.

 

[DylanDuluth]

I think I am going to take apart the risers and flush everything. The boat had been sitting for a while and I think I knocked something loose and caused a blockage. Replacing the thermostat, impeller, and fuel filter, too. I just bought the boat a few days ago. It was running great for a few days straight.