View Full Version : No Power under load - 86 MC 351 Inmar

06-07-2010, 08:52 PM
I finally replaced the points with a electronic switch from prestolite. Boat ran great first day. Second day had a couple of backfires when cold or underload. Third day boat back fired again ran for about five minutes died when waiting for another boat to finish it's run. It wouldn't crank. Took about 20 minutes of trying to crank before it fired up. It ran fine without load. Idle great, but once I tried to step on the gas with a skier it bog down and quit. If I feather it I could get it up to speed but not like a MC.

Not to lead any suggestions in the wrong direction but I am wondering if one of the back fires blew the power value. I didn't have any tools (my mistake it is a 86 but she is my other lady:o) to turn the idle screws.

Suggestions welcome.


06-08-2010, 09:39 AM
Sounds like your spark is way off. Check the installation of the ignition module and that the distributor was secured. Thinking timing got way advanced. Certainly possible that you blew the power valve with the backfiring. With it removed, if you can grab the narrow end and turn it inside the housing it is bad. Be sure to replace with the exact same power valve.

06-10-2010, 05:47 PM
had the same issue as you.. kepd dieing under load.. we fooled around all day trying to figure it out. ended up being a small vaccume hose that leads to the air filter on top of the carb that had fallen off... popped the hose back on and it ran like a dream!

06-11-2010, 05:08 PM
I guess checking your timing always should be done after opening the distributor.

06-13-2010, 09:35 AM
If your boat has points, I would check them. Make sure that they are tight & adjusted correctly. I replaced a set in one of my boats & the boat would stall & sputter over 1800 rpms. It turned out that the spring tension on that set of points wasn't strong enough.