Mercruiser 165 rough idle

[vanattitude]

I have a Mercruiser 165 2brl. that idles rough and stalls when the engine warms up. The problem was intermitent 2 years ago, but now does it all the time. I rebuilt carb (twice) checked fuel etc. and recently performed service bulletin addressing idle mixture flooding. Doesn't seem to be induction. How about ignition? I reset timing (improperly probably) last year, seemed to be ok but the problem was intermitent anyway. Any thoughts?

 

[Bondo]

Re: Mercruiser 165 rough idle

Ayuh,... When was it last given it's Annual Full Complete Tune Up,+ Service,..??

 

[vanattitude]

Re: Mercruiser 165 rough idle

It has been a while. I typically do progressive maintenance and apply grease to squeeky wheels. From an ignition standpoint, what steps can be made to ensure it is functioning normally?

 

[stonyloam]

Re: Mercruiser 165 rough idle

Since the problem seems to be getting progressively worse. Do a compression check to see if you have a weak (getting weaker) cylinder (especially #3 or 4). You can also pull the plug wires from the distributor one at a time to see if you get the same response when when each individual cylinder is not firing. A bad cylinder may indicate a head gasket/valve problem could be causing your rough idle problem. Good luck.

 

[vanattitude]

Re: Mercruiser 165 rough idle

Good tip. I'm going to try that on the hose right now. I had an impellor failure a while ago, which caused high water temp (pegged out at 240) Engine did not stall and I caught it quickly. No oil in water or water in oil. Sounds like i may have to start from scratch.

 

[Bondo]

Re: Mercruiser 165 rough idle

Sounds like i may have to start from scratch.

Ayuh,... Sounds like you should learn to do Preventive maintanance,...
Instead of Reactive maintanance....

Btw,... Is this the 6 cylinder 165, or the 4 cylinder,..??

 

[vanattitude]

Re: Mercruiser 165 rough idle

It is a 4 cycl.

 

[Bondo]

Re: Mercruiser 165 rough idle

It is a 4 cycl.

Ayuh,.... Sorry to hear that.... Do a Search here for "470",... You'll see what I mean..

That trip to 240? is probably going to come back,+ Bite you....

Good Luck....

 

[stonyloam]

Re: Mercruiser 165 rough idle

If you overheated it there is a good chance that you have a leaking head gasket and are doing damage to the valves. The compression test (easy, if you can the change plugs you can do the test) should tell you. Autozone will let you use a compression gauge for free. Good luck.

 

[vanattitude]

Re: Mercruiser 165 rough idle

update. Carb had two stripped helicoils on airhorn to float bowl. Repacd helicoils and rebuilt carb. runs much better and idle is great. However, when engine is warm it will not idle below 1000 rpm. continued rough idle wil cause engine to stall and will ocasionally lock up. lettinin it sit for five mintes frees it up and will start slowly.

when engine is at norml operatng temp (145') it has lots of blow by from vent tube. Also, there is lots of milky goo inside valve cover. I notice lots of condensation in carb after running around a bunch. Every thing above 1000 rpm is balls to the wall.

 

[dubs283]

Re: Mercruiser 165 rough idle

"lock up" ? does this mean the engine will not turn over??

lots of condensation and milky oil means you are ingesting water somewhere, exhaust manifold, blown head gasket, or even worse cracked head!! ouch!!

start with checking the oil for milkyness then for water/coolant in the cylinders and then a compression test

 

[vanattitude]

Re: Mercruiser 165 rough idle

Yes it won't turn over. If it sets for a couple of minutes it will turn over. slowly at first then normally. The engine oil and coolant are both clean. What do you think about the blow by? Seems like it has lots of it. There is lots of condensation on the spark arrestor and within the carb itself when this situation occurs.

 

[abj87]

Re: Mercruiser 165 rough idle

I'm betting on a blown head gasket, happens to these engines when you over heat them. 240 is damn hot for any engine. Have you done a compression check?

 

[vanattitude]

Re: Mercruiser 165 rough idle

Not yet, I didn't bring a test set up with me this week. I'll check it out, but I think you are on the right path. This seems to all have occured shortly after the impeller failure (which by the way was the result of starting it dry and running it briefly without water.) It's a tierd engine and has served well. I might pull the head and get it overhauled just for kicks. Would like to know the compression before hand to get a better idea of things before hand.