Mercruiser stern drive runs for 30 min then dies

We have several friends that have had the same issue - not sure it applies as I dont know mercruiser engines at all.. but its always the idle air control valve - they run for a while - then stall - then wont restart or take a lot of restarting..

like I say - not sure it applies to this engine - but something else to look at if it does apply

Such a common thing over here that our friends all carry spares

Steve
 
The quick electric check is to pull a plug cap off, and get somebody to turn the engine over, see if you get a strong pulsing spark when you place it close to the spark plug again.

Do ensure the bilge blowers have been running, you wouldn't want to get a Drone's eye view of your boat... :encouragement:
 
5teve said:
We have several friends that have had the same issue - not sure it applies as I dont know mercruiser engines at all.. but its always the idle air control valve - they run for a while - then stall - then wont restart or take a lot of restarting..
Click to expand...

If it was anything to do with lack of fuel a dose of easy start would get the engine to fire for a revolution or two !

Our local car repair workshop may have been known to use brake cleaning fluid to start reluctant diesels. :)
 
Looking a bit more into the Idle Air control - it stops it from idling and starting - doesnt stop fuel but stops air.. seem to remember the OP saying it cut out at revs. Certainly worth ignoring my diagnosis :)

Steve
 
Ladies and Gents - we have success!
Over two years, two boat mechanics, many many parts switched out.
A new ignition coil and the boat ran for over 30 minutes!
We took a 20 minute ride and came down off plane just fine. Boat idled, boat rolled along at idle speed, boat was cut off, STARTED right back up. Then ran another 20 minutes or so no problem, back down off plane, etc.
Yippie Ki Ehh! spent a couple thousand dollars more than I needed to, but an $85 coil and it appears that we are back on the water!
Thanks for ya'lls interest and suggestions.
 
flyinghull said:
Ladies and Gents - we have success!
Over two years, two boat mechanics, many many parts switched out.
A new ignition coil and the boat ran for over 30 minutes!
We took a 20 minute ride and came down off plane just fine. Boat idled, boat rolled along at idle speed, boat was cut off, STARTED right back up. Then ran another 20 minutes or so no problem, back down off plane, etc.
Yippie Ki Ehh! spent a couple thousand dollars more than I needed to, but an $85 coil and it appears that we are back on the water!
Thanks for ya'lls interest and suggestions.
Click to expand...

Lovely to hear. Another triumph for this forum and also for researching a problem and doing a job yourself with the help of others. I bet you are chuffed and now like your boat again

Dennis
 
Reviving this thread...
Reading the OP's description of his/her issue, it sounds nearly identical to what I've experienced recently on a Mercruiser 350 inboard with 860hrs on the motor in a year 2000 Tige 21i boat. Battery strong, fuel clean, she fires right up and runs for a little while, then after 20-30 minutes, she begins to run rough while at idle, sputters & dies, and will not restart. Initially suspected a problem in fuel delivery as a result of some temperature related issue. Replaced fuel filter (fuel/water separator) with no change, then went down the electric path as well and replaced the distributor cap, rotor, spark plugs. No change. Runtime got shorter. Restart delay after engine died got longer. Very frustrating, but I'm going to try the ignition coil next and will update this thread with results. In the mean time, if any others have additional suggestions or ideas, I'm not above receiving more virtual groupthink brainstorming or stories of prior successes/failures with similar behavior on your own boats.
 
Hi there. Not sure if you are already aware, or it’s been suggested already…but these things are notoriously famous for having issues with the automatic choke system. The Rochester in particular. It can all too often fail at the thermo coil arrangement, meaning the choke can stick on, off…or anything in between…but usually when she’s cold or in a state of half cold and half warm. Any engine I’ve had like this…the first thing I did with it, was to disconnect the system and lock it in the off position…just meant I had to pump the throttle a little from cold and hold the rpms until she warmed up and settled.
 
You must log in or register to reply here.

Share this page

Top