Loss of Power at WOT after +/- 20 min

[mlblakeney]

1988 Yamaha 130 ETLG - Pre-mix.

Hello all. New to the board and having a problem with the above referenced outboard. Two weeks ago boat left me stranded for the first time since I bought her 4 years ago. Engine started and ran fine for about 20 min. and then, after idling down for a few seconds she wouldn't get back on plane, topping out at 3200 rpm at WOT. I throttled down and engine died. I could smell fuel, removed cowling and saw gas dripping out of lower carb. First thought was stuck float or needle valve not seating and thus flooded, so I unplugged fuel line and tried to crank her. Engine would turn over but not start. Reattached fuel line and pumped bulb. Tried again and no start and was towed in.

Last week I removed and cleaned both carbs, both looked very clean, floats and needle valves in good shape, ports clean. Replaced all fuel lines, cleaned fuel filter, reset floats and put her all back together. Engine started and idled fine on the mufflers so took her out today. Engine ran better than ever for about 20 min., when the same problem cropped up. After slowing to pass a small boat, couldn't get back on plane; only about 3100 rpm at WOT. squeezed bulb (which was hard) and engine immediately died. Raw fuel was again dripping from bottom carb. After sitting for about 30 min. engine started and ran fine on the way back home, but still getting fuel dripping from carb. I've checked everywhere but cannot see where fuel is coming from. Pulled plugs and 3 were clean but bottom port side plug was wet. Could a small hole in the fuel pump diaphragm be sucking raw gas into the crankcase and causing my problem or is there something I'm missing? Any input would be greatly appreciated.

Mike

[mitch]

check your fuel pump for holes in diaphram

[mlblakeney]

Will do and post back my findings. Thanks for your input!

[mlblakeney]

Okay, Still having the same problem. Again, 1988 130 ETLG, Premix gas. Engine runs great for 20+/- minutes and then suddenly looses power and bogs down. Sometimes it will kick back up and run fine, but other times the engine will die. If it dies, I will not restart and smells flooded. If you let it sit for 30 minutes or so, it will start and run fine, sometimes for the rest of the day, other times for 20+/- minutes and the process starts over again. I have cleaned and rebuilt both carbs, replaced fuel pump, replaced plugs, replaced all fuel lines, installed a new fuel water separator with spin on filter, replaced bulb and fitting to engine. I am starting to think I have an electrical issue. Any thoughts on how to track this down would be much appreciated.

[bumperfood]

Did you actually overhaul the carburetors with OEM parts or just clean them, reusing old parts? Did you reset the float height, making sure that it didn't hang up anywhere?
As far as electrical is concerned, you should be able to check that fairly easily, however you will need to get it to act up again, as it must have spark up to at least that time. Your initial testing will have to be on the water, so either a reliable kicker or a friend, willing to tow you in would be desirable. Bring the tools along so that you can check for spark.

[robert graham]

Sounds sorta like a bad float valve seat, maybe sticking some...works a while, then don't work, flooding carb. Some of these float valves have a rubber ring on the needle or in the valve body. Good Luck and let us know what you find!

[marinermikes]

Just a thought but easy to try. Try running it with the cowl off and see what happens. Some times the CDI unit will start to go bad and lose spark when it gets warm. When you slow down or stop it builds a little extra heat under the hood and causes it to malfunction. It may not be your problem but it's easy enough to do.

[mlblakeney]

Thanks for all the suggestions. Yes, I did rebuild the carbs using OEM parts and reset the float valves. I think I'm going to get her out on the water tomorrow evening and see if I can get it to act up again. Sparks are easier to see in low light. Actually was able to diagnose an issue on a friends Evinrude by running it at night with the cowl off. I will post back my findings and progress. Thanks again for the input.

[99yam40]

A spark tester from auto parts store or a inductive timing light would be a good thing to take along to see if all plugs are getting spark.

For fuel to be coming out of bottom carb the needle is not seating properly, maybe trash not letting it seat properly. Does not take much to do it, and flushing the lines out real good before hooking up to cleaned carbs is always a good step