1987 OMC 3.0 idle issues

[t-swans6]

I have an 87 bayliner capri with a 3.0 My issue is that once the engine warms up it doesn't idle smooth at all and usually dies if you don't play with the throttle and also starts hard when hot, you have to play with the throttle to help it get going. The previous owner had the carb replaced with a seirra brand carb, not sure why though. I have tried adjusting the idle mixture screws in and out along with the idle speed screw and thought I had it really close last summer but the first time out this year was pretty bad. Also once you get going it runs really good at all rpm ranges. Only maintenace I have done is spark plugs, checked timing wich was really close, fluids. I'm leaning towards a carb issue but wondered what you guys thought?

 

[HT32BSX115]

Re: 1987 OMC 3.0 idle issues

Howdy,

It's likely a fuel issue. maybe a float or choke adjustment problem. (I assume you have good fuel flow thru the filter and fuel pump?)

Even rebuilt carbs are screwed up right out of the box.

 

[Kainon]

Re: 1987 OMC 3.0 idle issues

Need to check the points, Distributor Cap and Rotor. Best way to adjust the idle mixture is set the idle close to 800
put the boat in the water, tied to dock or trailer, put in gear, let engine warm up, make sure choke is open and timing is set.
turn mix screws in until it starts dying down, then out till starts dying down, then divide turns by 1/2

listen closely as possible to the sound of the engine.

 

[aerobat]

Re: 1987 OMC 3.0 idle issues

i had a similar problem with my volvo 3.0 and it turned out to be to much heat in the engine compartment. i have the engine blower on one side which sucks the air out and fresh air intakes on both sides. running the blower all the time let the problem dissapear , and in my boat the blower reduces engine room temperature really significantly.