Problems with idleing

[jennifer1762]

Okay guys I am new at this I screwed up the last one so I will try again!! My boat is a 1990 Larson Mercruiser 5.0 serial number oc856419. We have replaced the following items spark plugs and distributor cap and the wires, igintion koll (sorry I can't spell this) Last year we rebuilt the carb and replaced impreller pump cause it was running hot and tremostat. Now to the problem... Will idle fine at 1000 Rpm anything lower jumps from six to nine and will end up dieing out. Last year we winterized and there were no problems and now we can't even enjoy are loan payment. Please help us I thank you!!

 

[Don S]

Re: Problems with idleing

Sounds like you are throwing parts at it in hopes of the problem going away.
Who rebuilt the carb, and was it done by the book. Not talking a "take most of it apart and put some new gaskets in it after spraying with carb cleaner." rebuild That is not a rebuild. It's more of a "Spent money, still don't work" throw money at it type job.
Do a compression test, check your fuel filters for water, confirm the timing, carb idle mixture settings. There is no "Book" setting for mixure. It's done with the engine running. A running vacuum check would be another test to run to see what is going on.
You do have an OEM service manual don't you?

 

[jennifer1762]

Re: Problems with idleing

We bought rebuild carb kit and a mechanic did it. NO we don't have a manual!!
jen

 

[Bondo]

Re: Problems with idleing

Ayuh,.....

Installing a Carb Kit is a 50/ 50 Bet,... At Best....
And,... It was done Last Year.....
It doesn't take much Water or other Crap to clog it up again....
Have you changed the Fuel Filters lately,..??

 

[searay3]

Re: Problems with idleing

I may be off base here, but once the carb has been rebuilt, it still needs adjusted on the motor running. Didn't see where you mentioned how/who installed the carb. Some adjust by feel or sound. My old man did it by watching the aircleaner stud. He would play with the mixture screws until it stopped shaking. Some use a vacuum guage. Adjust the screws for top vacuum and slow the idle down. Repeat until you are at 6-700 rpm and smooth. My 2 cents.....

 

[jennifer1762]

Re: Problems with idleing

So we took the boat to the shop!! And found it was the number three cylinder is giving no compression. If we would have let him go furthur he would cost us three hundred more to look at it and see exactly no compression was not coming from that cylinder. All the others were fine. They said it could be a headcasket or other thing to replace the head casket would cost 1000. Were at a loss on what to do...
jen: anyone help us please

 

[erikgreen]

Re: Problems with idleing

Did you winterize it or did someone else?

Do you live in a part of the country that has below freezing temps in the winter?

 

[Bondo]

Re: Problems with idleing

Were at a loss on what to do...

Ayuh,...... Learn how to turn Wrenches is the Best I can do....

Your boat is Broken,.....
Either yourselfs have to Fix it, or Pay somebodyelse to do it.....

It's worth virtually Nothing if it ain't Runnin'..........

They said it could be a headcasket or other thing to replace the head casket would cost 1000.

That would be a Best Case senario,... It could also be Much Worse.....

 

[Don S]

Re: Problems with idleing

A head Gasket would not cause Zero compression. When they get it apart, I would bet they find a tuliped valve, and probably the seat beat out of the head in extreme cases. Don't let them try to replace a seat. They just never seem to stay and most times destroys a piston when they let go. May take a new head if the seat isn't grindable. If it is, usually a new valve and valve job and you are back in business.