1999 Volvo Penta 3.0l developed misfire

[scb1712]

Hi all,

Ah - the joys of boat ownership continue. First, i have a 1999 Volvo Penta 3.0l GS-PEFS engine. Had some overheating issues last year but all of those are now resolved and she's been running pretty well so far this year.

I know that the carb needs a rebuild as i don't think the high speed jet is working optimally as she bogs a bit when you give it full throttle. While not ideal, it has certainly been manageable and hasn't really caused any performance issues even when water skiing or tubing. Generally, when you give it full throttle, it would bog momentarily, and then get up and go accellerating smoothly up to about 4500 rpm.

However, this weekend it seemed to start a bit of a mis-fire. The engine sounded "off" and she wouldn't accellerate normally. After shutting it down for a few minutes, it started up fine. However the misfire appeared intermittantly while we were trying to ski, as it would bog more noticibly and not accellerate smoothly after the initial bog. Eventually after a rest and some easy running, she ran normally for the trip home.

Could this be an extension of the carb problems? Perhaps some bad gas or should i be looking elsewhere? Also - i've read in similar threads that i should consider changing out the plugs, wires and cap. Can i use parts from the local automotive store, or do i need to get Volvo ones for 6x the price?

Thanks!

 

[ewenm]

Re: 1999 Volvo Penta 3.0l developed misfire

that secondary jet you are talking about is actually a power valve, its like a little vacuum diaphram that opens based on load, they can fail and you would get a flat spot or lean condition, that could be catastrophic in a boat motor, they are easily replaceable and simply screw into the metering block, thats the 1/2 inch thick block between the carby and the fuel bowl, they usually have size info stamped on the edge

the throttle fuel pump ( on the carby) has a little link that has an adjustment, and you need to check there is no slop in the linkage.

on the throttle shaft there is also a cam that effects the accelerator pump shot and has two positions ( well at least it does in the automotive versions and there is a wide variety of cams available for tuning purposes, or at least there used to be when i was young and mucking around with Holleys on V8,s)

you can get spark plugs at an automotive parts store, leeds too, but you would need to know if you have suppression or solid core leeds.

as for the distributor cap and rotor i think they have no comparable product in the automotive world so you might have to order them from a marine type parts supplier

hope that helps

 

[scb1712]

Re: 1999 Volvo Penta 3.0l developed misfire

Thanks for the suggestions. I'll have a look this weekend and see if i can figure out if there are any adjustments to the carb that i can make.

Would the carb issue have anything to do with the mis-fire or is that a spark issue?