1986 175hp merc won't idle

[harris2520]

I have a 1986 175hp 4.3L I/O mercruiser V6 GM MCM175, Thunderbolt IV, Alfa outdrive. It has been running great but the last time I was out it was a bit choppy so I only crused about 25mph. When I came down to an idle she shut down like I had something wrapped around the prop. I didn't. But I can't run any more except at HIGH RPMs, 1200 or higher. I pulled the carb (Mercarb 2 barrle)and did a complete rebuild on it. No help there. I'm going to try the spark plugs tomarrow.

 

[The Marine Doctor]

Re: 1986 175hp merc won't idle

Check the driveunit for gear oil.<br /><br />TMD

 

[harris2520]

Re: 1986 175hp merc won't idle

Yes that was my first thought also. I forgot to say that. It was 1" low and dark green. No water, no solids, no unusual oders. Filled back up with new gear lube. Thanks.

 

[harris2520]

Re: 1986 175hp merc won't idle

OK, Spark plugs replaced. Looked OK. Timing at the lowest ilde I could get was WAY BTDC. Played with timing and ilde screw to get 8o BTDC, (as per manual & id plate). Still ildeing at around 1500 rpm but nice. Goes into gear smooth in drive-way. Still it doesn't sound like a happy motor. If it stops raining here at Lake Erie I'll put it in the water and see what she does.

 

[The Marine Doctor]

Re: 1986 175hp merc won't idle

It has to idle at 1500rpm's??? <br /><br />That is too high...you might have a serious problem if it will not idle lower.<br /><br />Or and air leak <br /><br />TMD

 

[harris2520]

Re: 1986 175hp merc won't idle

Thank you Dr. I forgot everything I knew about motors as a kid. Its been a long time since I got my hands dirty. Sorry. Please see I/O repairs for the rest of the story. I figured it out once I got her in the water and played around with the mixture and idle screws.