RebeccaBurg
Cadet
- Joined
- Nov 26, 2011
- Messages
- 24
Seeking advice from the more experienced, a year 2002 2-stroke 8hp Yamaha has me at a loss.
It looses power above about 1/3 throttle and will die out unless I throttle down back to near idle. Idles smooth, loves low speeds. Went through all the usual suspects: -compression is 130 in both holes (is that a bit high?), -my cheapie spark tester shows spark, -Prop good shape, gear box good, -boat bottom clean (newly painted even!), ran great on this same small 12' boat years ago & boat is not overloaded. -Carb rebuilt and so clean I can eat out of it, -fuel pump diaphrams are 1 year old...a suspect maybe, but still so new, -water passages clean & new t-stat, -spark plugs & gaps to spec, -peeked under exhaust cover thinking there was build-up & back pressure, but is clean and inspected rings from there: they're great shape!, throttle linkage and timing seem okay according to shop manual. Went thru entire fuel system- replaced tank, bulb & hoses and have always used non-ethonal fuel. INstalled clear fuel hose to fuel pump to watch for leaks, but is solid. Also, the kill switch isn't acting up either. Reed valves look clean and normal, but not sure how to test 'em.
Whew! sorry for all that ramble, but need to show all the puzzle pieces.
Would the ignition parts be suspect? The ign. coil shows a only bit more resistance than what's specified in the manual. The pulser coil reads 115 ohms instead of the specified 92-112 ohms. Does such a small bit out of spec make enough difference in the performance at higher RPM? Hope to learn more before investing in replacing these $$$ parts. Not sure what else to blame, since everything seems so, well, darn okay.
meanwhile, will peek at that 1-year old fuel pump's rubbers & will squeeze bulb when power starts to drop to see if that does anything...
thanks in advance for any insight!
Becky
It looses power above about 1/3 throttle and will die out unless I throttle down back to near idle. Idles smooth, loves low speeds. Went through all the usual suspects: -compression is 130 in both holes (is that a bit high?), -my cheapie spark tester shows spark, -Prop good shape, gear box good, -boat bottom clean (newly painted even!), ran great on this same small 12' boat years ago & boat is not overloaded. -Carb rebuilt and so clean I can eat out of it, -fuel pump diaphrams are 1 year old...a suspect maybe, but still so new, -water passages clean & new t-stat, -spark plugs & gaps to spec, -peeked under exhaust cover thinking there was build-up & back pressure, but is clean and inspected rings from there: they're great shape!, throttle linkage and timing seem okay according to shop manual. Went thru entire fuel system- replaced tank, bulb & hoses and have always used non-ethonal fuel. INstalled clear fuel hose to fuel pump to watch for leaks, but is solid. Also, the kill switch isn't acting up either. Reed valves look clean and normal, but not sure how to test 'em.
Whew! sorry for all that ramble, but need to show all the puzzle pieces.
Would the ignition parts be suspect? The ign. coil shows a only bit more resistance than what's specified in the manual. The pulser coil reads 115 ohms instead of the specified 92-112 ohms. Does such a small bit out of spec make enough difference in the performance at higher RPM? Hope to learn more before investing in replacing these $$$ parts. Not sure what else to blame, since everything seems so, well, darn okay.
meanwhile, will peek at that 1-year old fuel pump's rubbers & will squeeze bulb when power starts to drop to see if that does anything...
thanks in advance for any insight!
Becky