mariner 150 troubles

[Krow Daddy]

i have a mariner 150hp that has had some trouble running lately. at first, it just had trouble starting up, then it would run really rough. eventually it wouldn't start at all anymore. took it to be serviced, they replaced some old worn out spark plugs and some faulty throttle positioning sensors. had it back for about two days, and we were sitting out in the bay, idling in neutral. all of a sudden, completely unprovoked, the engine revved up to a high RPM and got pretty loud, then just went back to normal and we figured we'd ignore it for the moment. Minutes later as we pulled away in the channel, the engine cut off. after a few tries, the engine started again and is running roughly once again. also, before the second die-out, while it was still working, it was working the best we'd ever had it run, but it seemed smokier than normal. <br /><br />can anybody offer any advice without me having to spend another $2000 on it?

 

[The Marine Doctor]

Re: mariner 150 troubles

Sounds like an EFI engine if you have Throttle Position Sensors. <br /><br />Generally if the engine starts to race it will be because the IAC has opened up...leans out the mixture. Increasing the idle. IDLE AIR CONTROL.<br /><br />I would suspect that you have a faulty sensor that is triggering the IAC.<br /><br />The place that you are having it serviced at should be able to hook it up to their DDT. This should tell them right away what has failed. They can also do Cylinder drop tests to find out if it more serious.<br /><br />TMD