3.0 Volvo Penta GS Shakes while idling

[4winnsskipper]

Greetings,

My 96, volvo penta 3.0 GS shakes while idling, anything above 1,000 rpms and it doesn't shake. at any rpm it stays solid, it doesn't surge or die or anything, it just shakes more than i would think an engine idling should. nothing violent, just u can feel the boat shake a little while it idles. right now i have it idling around 800 on the stock tach...and shakes...the plugs have been replaced, new cap new rotor. boat runs and drives like a dream otherwise and plans out at 40mph with just me in the boat, no issues there, no stumbling or anything just shakes at idle.... i just ordered and received new spark plug wires since when removing the old ones the metal clip that attaches to the plugs came off on two of the tires and i recrimped/attached it and was thinking that might be an issue.......btw the engine only has 38 hours on it, spent most of it's time sitting properly winterized, fogged, etc. no leaks, no overheating at all, nothing, ONLY issue is a shake at idle.....gas is new also, 89 octane per the volvo penta manual for it. just lookin for ideas...my thought is the carb could use a cleaning/rebuild.......perhaps just an adjustment on the carb? i know nothing about carbs, but plenty about the rest, i've only worked on FI car engines....any other ideas?

 

[Don S]

Re: 3.0 Volvo Penta GS Shakes while idling

You probably only need to richen the idle mixture, not rebuild the carb,
Do a full Tuneup/Summerization if it hasn't been done this year. I doubt you need a carb rebuild. The 3.0L engines should idle between 650 and 700 rpm.

 

[4winnsskipper]

Re: 3.0 Volvo Penta GS Shakes while idling

You probably only need to richen the idle mixture, not rebuild the carb,
Do a full Tuneup/Summerization if it hasn't been done this year. I doubt you need a carb rebuild. The 3.0L engines should idle between 650 and 700 rpm.

Don - I actually followed your summerization this year, and winterization articles - appreciate that!!! How do i richen the idle mixture? Im sure it's just a screw, but which one, looking at the carb theres a few screws on it. Appreciate the help/time Don.

 

[Don S]

Re: 3.0 Volvo Penta GS Shakes while idling

What's the full model number or even the SN for your engine?

 

[4winnsskipper]

Re: 3.0 Volvo Penta GS Shakes while idling

What's the full model number or even the SN for your engine?

Engine has OMC cobra ID sticker, drive is volvo penta SX cobra, Air cleaner says volvo penta, so im guessing i got one of omc's left over GM 4 bangers and Volvo's drive / accesories..

Engine Model : "302 CPNCS"
Serial Number: "t01292280"

Not sure if that helps you tell me where my idle mixture adjustment point is or not, its a holley carb, which im guessing is on just about every IO....thanks for the help Don.

 

[180shabah]

Re: 3.0 Volvo Penta GS Shakes while idling

at any rpm it stays solid, it doesn't surge or die or anything, it just shakes more than i would think an engine idling should. nothing violent, just u can feel the boat shake a little while it idles.....
....i've only worked on FI car engines....

Just wondering if this might be a case of inexperience with "HUGE" 4 cylinder engines that lack balance shafts and hydraulic mounts????

 

[4winnsskipper]

Re: 3.0 Volvo Penta GS Shakes while idling

Im pretty sure its not suppose to shake like this, i've rebuild many a motor, just enver used a carb on any of them. engine is solid at 1,000 + rpms, like any engine should be, but shakes enough to shake the boat anywhere below 1,000 rpm. the engine does not die, surge, or anything like that, stays solid at whatever rpm, all the way down to 600 rpm, but shakes more than i think an idling engine should......i will take video of it soon.....it sure seems like a bad a/f ratio, so im hoping someone can tell me how to adjust the a/f on the carb....thanks

 

[Don S]

Re: 3.0 Volvo Penta GS Shakes while idling

They should idle fairly smooth and accelerate normally.
The mixture adjustment is on side of the plate between the float bowl and the carb body. It's a Holley.
You may just need a carb rebuild, possibly a partially plugged idle passage.

 

[4winnsskipper]

Re: 3.0 Volvo Penta GS Shakes while idling

Don - I toke two pictures and labeled the three screws that might be what your speaking about, what do each of these three screws do? Im thinking arrow "B" adjusts idle speed??? Thanks again for the help... see attached pix.

 

[Don S]

Re: 3.0 Volvo Penta GS Shakes while idling

B is idle speed, A and C are mixture.

 

[4winnsskipper]

Re: 3.0 Volvo Penta GS Shakes while idling

how would you recomend adjusting these? turn both equal amounts or one a different amount? Im assuming clockwise is leaner and counter is richer on both screws? THanks for the help don!!!!!!

 

[Reel Poor]

Re: 3.0 Volvo Penta GS Shakes while idling

turn both equal amounts or one a different amount?

Equal amounts is correct

Im assuming clockwise is leaner and counter is richer on both screws?

Correct again

Most Hollys will adjust when the screw is within a 1/4 to 1/2 turn off their seat. Adjust air mixture screws for maximum RPMs. Then adjust idle speed to 650/700 RPMs.

 

[Don S]

Re: 3.0 Volvo Penta GS Shakes while idling

Warm the engine up and make sure the choke is open.
Disconnect the throttle cable, and adjust the idle to around 700 (Use a shop tach and have it so you can see it.)
Turn the screws in, one at a time till the rpm drops, then back it out to highest rpm plus an additional 1/8 turn (NO, more is not better). Repeat on the other screw.
Adjust the idle to 700 again and repeat. Do this several times.
I like to goose the throttle after each adjustment to keep it from loading up from excess fuel and to be sure it's where it should be.