Motor issue

[Rogrock]

Hey guys, I've got a 1996 60 horse Mariner that had sat for a while before I bought it a couple of years ago. I have trouble with it bogging down now and then after running WOT. RPM's drop from around 4800 to 3000. Motor is not overheating, and there are no alarms sounding. Plenty of oil in the tank. After sitting a few minutes, I can restart it and it will pop back up to 4800 RPM's. I have had the carbs cleaned once and have changed fuel lines. Some suggest I need the carbs cleaned again and someone else said it could be an ignition coil. I run Stabil in each tank of gas. Any thoughts? It's annoying when you can't count on things running well. Thanks.

[noelm]

you need to do some very basic troubleshooting first, do you have a genuine manual for your motor? if not, buy one, now, remove the spark plugs, do they all look the same? do a compression test while they are out, replace the spark plugs anyway, they are cheap, do you have a good fuel filter installed? if not, do it now, you can clean your carbs in the morning, hook them up to a dirty tank, and you will clean them again after lunch! can you run from a complete remote tank and fresh fuel and hose? do these simple things first and get back to us.

Edited August 9, 2011 by noelm

[davidkuhlmann]

Pull the ECM off and see if it is grounding to the block. There is a plastic coating on the back of it and if this is the problem you will see a melted area. Not saying this is the problem but something to look for. One other thing that comes to mind is possible vapor lock. Check the tank vent for obstructions.

[noelm]

ECM on a '96 Mariner 60?

[davidkuhlmann]

I used ECM for lack of a better word. There is a box that controls spark. I had a 96 Mariner 40 and the same problem happened. I call all the Ignition control modules ECM's.

[SCAngler]

coil or power pack

[Erie Skipper]

Agree on checking the plugs as well; if even one is the wrong plug, it may be getting too hot and regapping itself or not hot enough or whatever--replace the lot and make sure you have the proper plug that your motor calls for.

[Rogrock]

Thanks for the thoughts. I have had the motor looked at by 3 different mechanics. None could pinpoint the problem because they couldn't replicate it. To date they have, in this order: Replaced the power pack (boat wouldn't get over 3000 RPM's), cleaned the carbs and put in all new fuel lines, checked the compression (all very good), replaced the in-line fuel filter, run the motor on their "dyno" for 1/2 hour--no problems. I just replaced all 3 spark plugs (they had the right ones in, but they were a bit "charred"). Will be taking the boat out Thursday to see what happens. I haven't yet had the ignition coil checked, so if the problem persists, that will be my next step.