sounds like your float valve in your carb. after boats, cars or anything that has a carburetor sit for a while crap in the float bowl can get or just an old valve and seat don't entirely stop the flow of gas from the bowl. dirt can get in the valve or whatever may be in the bottom of the bowl. if it is the float valve it may start to work better just by running the boat but the sure fix is to replace the float valve and clean the float bowl. sometimes just cleaning everything works too. my 89 would do the same thing and the 87 did the exact same thing on its first run. I put in a new valve and it ran perfectly. hope this helps