79 Ski Nautique - 351 Idle and Stall Issue

Thanks guys. I pulled the primary fuel bowl and metering body apart and indeed it was all gunked up, so cleaned it up and rebuilt it. She's purring like a kitten again and idling as expected. Gonna water test this evening, so fingers crossed that was the main issue.

Jason,
It sounds like it's time for a carb rebuild.

Hi All,

Having some issues at low speed and idling. I'm by no means a mechanic but am quite comfortable doing all my own maintenance and moderate repair jobs.

At the end of last season the boat was running smooth and pulling strong. I did a full winterization (I live in the Seattle area) including fogging the carb with Marvel Mystery Oil.

It's worth mentioning the boat sat outside for the winter, but has a high quality custom cover that keeps it dry. At one point some water got in because the cover was not put back on correctly, but I caught it pretty soon and dried the boat out. Previously the boat has been garaged, but unfortunately that's not an option any longer.

Anyway, the boat fired up on the trailer and seemed to run as expected. It always seems to take a little while to warm up and be able to idle normally.I often have issues starting after the boat has sat for a while. This is always solved with some starter fluid sprayed into the carb. When in the water and the engine is cold it would always die the first time I put it into gear. However, it would fire right back up and be good after dropping into gear the first time.

Dropped the boat in the water today to load test before we head away next week to Banks Lake and found the boat idling very rough and stalling unless I kept the throttle up and RPM stayed 1000+ (unfortunately my tac is broken, so judging by ear). At low speeds the RPM tended to roam until RPM's reached 1.2-1.5k. Seemed like very uneven fuel flow in general at low RPM. Seems to me the stalling was due to it running to0 lean vs too rich.

However, the boat seems to run strong with more throttle. We didn't tow anyone today, but pickup was good and we easily reached 35-40 mph without pushing too hard.

I have relatively new wires and distributor cap (3-4 years old, but only running 20-30 hours a season). I checked all the plug wires, and distributor cap. All connections seems fine, and there was no change after I re-seated all connections. Not sure how old the plugs are, but I believe they were new when I bought the boat in 2011.

I'm guessing this is a carb issue, but obviously am not sure. I pretty much have tomorrow to try to figure this out as we leave on Wednesday. Hoping it's something simple!

Any feedback/advice for trouble shooting is much appreciated!