Nedd help with a Merc-problem I have seen B4.

MajBach

Chief Petty Officer
Joined
Jun 21, 2003
Messages
564
I know I have read of a similiar problem here before but I have not been successful with doing a search. Perhaps it was a different brand of motor and not a Merc.<br />Anyway, my uncle has a 9.9 (don't know how new but has an electric start). He has had a persistant problem with it running at any decent rpm at is coughs and dies. It starts and idles fine and even runs OK for a few minutes then it dies and anything much past idle. He must let it sit for a short period before he can start it and again it will die as soon as he applies any significant speed. One observation he has noticed is that it runs 100% fine when the cowling is removed.<br />He took it to a mechanic who looked at it and stated that he found a bad ground and successfully ran it in a tank at WOT just fine. Uncle assured him that this was not the problem, and sure enough, the motor still sufferred the same symptoms once he had it back. Two mechanics are still baffled by this but one has suggested that it is an defective electronic ignition control box. Apparently this little unit is protected by a think coating of epoxy and the mechanic thinks it might have a crack that expands when the motor is warm - causing a bad ignition. I think this is a reach. Problem with this is that these units cost major $$$$ and you cannot return them if they are not the problem.<br />I know I have read here of motors with similiar symptoms that turned out to have exhaust leaks. The gases would build up inside the cowling and thus choke the motor. This would explain his problems.<br />Can somebody elaborate on this or point me to the post that I am referring to?
 

The Marine Doctor

Commander
Joined
Jul 25, 2003
Messages
2,177
Re: Nedd help with a Merc-problem I have seen B4.

Check for a blown base gasket or exhaust cover gasket.<br /><br />As for the power pack heating up and stops working, this is possible...but not likely the way the Tech told you it is. The powerpacks are sealed with that gel to keep them dry. If there was a crack, you would have water in there all the time and it should cease to function.<br /><br />Btw...if you pull the cowling off and there is sufficient exhaust to kill the engine, you should see it.<br /><br />TMD
 
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