Sounds like one of the following
1. Top Diaphragm has gone bad- replace
2. Check filter in bottom and clean it.
3. Bottom pump diaphragm has gone bad -replace (just been through this recently)
4. Crank case hole blocked or obstructed, doesn't take much.- make sure it's clear, or completely block it and pulse port connect diretcly to the crank case.
5. Change your spark plug, had a new one go bad the other weekend after a good dunking.

Okay - here's the list of changes I have made going into the weekend... Probably too many at once, but some are just maintenance type things

took out the home made bag mount (think it was causing an issue - and I may be able to burp the bag better)
Reset the needles to 2 on low, 1 1/8 high
Changed the diaphram
Put a jumper wire on the ground lead of the coil to the case
Cleaned the bullet connectors with 600 grit paper
Pipe is at 12 -will adjust at the pond if necessary
Checked fuel line
Changed spark plug (will check gap when I find my guage or buy a new one.)


Did anyone think it was too "wet"? I added some negative to the strut for the runs in that video, I think given the right conditions it would blow off the way I had it set before, but I scrubbed off a lot of speed. I havent put a GPS in it, but I'd say I may be around mid 50s with it in the video, and I'll bet it was closer to or over 60 when it was loose. Despite the "missing" or "cutting out" it was doing. I think that was adding to it possibly blowing off because it would pick the nose up when the power came back.

Oh and I'm trying to figure out which crankcase hole BigFishBob mentioned. If its for a water pump, there is none on this boat.

unless im missing something the only hole i know of is the little hole just under the intake runner (it works the fuel pump).when you pull the insolator block off you will see it. as far as set up i would get a tach. and keep checking the rpms its a good tunning tool. i hope everything works for ya you shur did change alot

Thanks. I may consider a tach... I did change a lot, but a lot were minor, (needle adjustments, cleaning contacts, diaphram, etc) but it feels like I threw the kitchen sink at it. One other interesting note - I went to check the throttle after I put the motor back in the boat - turned on the radio, then the receiver - rudder but no throttle. Checked the wires, nothing. Looked at the failsafe - not even a green light (or red for that matter). Plugged the servo in directly, voila, throttle. Tried a spare failsafe - worked fine. That may have been the problem the whole time. The plot thickens..... If it runs - one of these things did it!

I'll have to wait to see if anything I did fixed it. I went to the river this morning, and the wind was kicking a little more than I would like to see to test a boat. Couple that with a kayak as a retrieval boat, 50 degree temps, and I thought better of it.

okay - I got a chance to get it out this morning, despite the cold. And the survey says: it was WORSE! Happening about halfway thru our straight, and then maybe a time or two by the time I enter the corner. Running half throttle the boat would run okay for a lap, and then start to do it again at half throttle. I tried going richer, it got worse yet. Very frustrating.

This may sound a bit obvious, but have you tried a fresh batch of gas? Worth trying if you haven't already.

Do you have other motors that you know run well? If so, after trying fresh gas, a simple thing would be to start swapping parts from the working engine to this one. Start with carburetor then ignition components.

Before pointing the finger at the internals, rule out all externals. Might want to also check the coil to flywheel gap, to make sure they're not rubbing. If you are using zero drag seals, looks for signs of leakage. If you are using a stock carburetor isolator, check to make sure it's perfectly flat on both sides. Try new gaskets there. That's a bad area for air leaks. It typically gets worse everytime you take engine apart and reassemble.

Try fresh gas......