zenoah troubles

[LuvEvolution]

I just bought a used 1/8th scale Pro Boat Miss Budweiser. I know from reading on here what you guys think about them, but for the price I payed, I couldn't refuse it. I plan on making all the mods to it that are talked about on this forum, but I do have a very specific question about the Zenoah engine.......I'm having problems with running the engine. I can run a complete tank of fuel through it and the boat runs fine, but fill it and try to run it again.......NO GO!!! It will rev up fine on the stand, but as soon as it hits water, it bogs right down and picks up when you turn right, then the same thing when you straighten out again. Since I'm extremely new to gas motors, I can only try to guess what the problem is.......I almost want to say it's too lean, but like I said, I can only guess at this and I don't want to wreck my engine. To add to the problem, I wasn't given the manual for the boat, so I'm not even sure how to set the needles up properly. knowing Pro Boat, I'm sure that procedure is completely screwed up also. LOL. Any help would be appreciated before my next trip to the lake. thanks guys!

[Mike T]

Remove the carb, then remove the plastic heat isolator block. Look at the back side of the block (the part that goes against the engine) and see if the steel reinfocement sleeves have crept out and are keeping the block from seating fully on the gasket. This will allow air to leak into the engine, and lean out the the mixture. If that has happened, either sand them flat on a piece of wet sandpaper on a sheet of glass, or buy a new isolator block. Put it back together with a new gasket if the old gasket was damaged by the sleeves. The needles on the stock 260 carb (#644 Walbro) are set at Low 1-1/2 and high 1-1/4. If it is too lean, it will bog when accelerating. There are other possible causes of bogging down - pipe too short, carb fuel screen blocked, bad diaphram, air leak in fuel lines, etc., etc.