kenfyoozed
New member
I have a Yamaha outboard that runs fine at idle but once you shift into gear it has no power at all. Here is what is known.
1. The motor started life out as a 1997 Vmax 150. It somehow blew a hole in the #6 cylinder. Still not sure of cause. Motor was then given to my brother who put it on the boat.
2. A used powerhead was bought.--- this is an area that is grey to me. My brother was told that this used power head was the same block as the vmax. Upon me getting this boat to work on it I found out the two powerhead look the same but they had different carbs and different flywheel.
3. Used powerhead installed with the proper base gasket.
4. All components from the blown motor were swapped over to the used power head..ex.. carbs, heads, intake manifolds, all electronics, everything that could be swapped was. All new gaskets were used.
5. Carbs from blown engine rebuilt with kits. Each soaked in berryman carb cleaner bucket for 15-20min, flushed with water, ran 2 cycles in dishwasher, back for another 15-20 min soak in berryman, flushed with spray brake cleaner, all passages cleared with compressed air then alcohol flushed followed by final flush and spray of aerosol carb cleaner. All passages seemed to flow as needed. All jets, and other internal parts were done the same. Float height checked and all resembled per the manual.
6. 2 new fuel pumps installed
7. New fuel lines installed from boat to fuel pumps.
8. Fuel lines checked for tightness from fuel pumps to carbs. These lines seemed ok. They do not leak fuel anywhere.
9. Carbs linked and synced and all open together in unison.
10. The used powerhead did not have a pulser coil that could be advanced, the blown engine did so we swapped the blown engine pulser coil so it would work with the control arm and time with carbs. We used the used powerhead flywheel as the inside magnets looked the same as the blown engines flywheel. This was all set per the manual but I could look at this again.
11. New impeller water pump.
12. Ran some marine engine chemicals through the water passage to clean them very good. The thermostats and poppet valve are removed to allow full flow of water to the heads.This was done in short term to rule out any issues with thermostats.
13. I have checked the spark gap and its within range. As well as all the coil packs test out. But i could retest to confirm.
14. Oil injection system was removed. Oil level float was tapped up to mimic a full tank. All hoses and ports were capped.
15. Sometimes I do get an alarm, but do not know what it is from as I have no electronics on this motor yet. When the alarm sounds i can unplug both temp seniors and the alarm goes away. This makes me assume this alarm is only the water temp. It took about 30 min of testing last time before the alarm came on.
16. Compression test shows #110-#120 on all cylinders.
This thing seems to idle fine in Neutral, and will rev really high in Neutral. Place it into gear with no throttle and it wants to die, try to rev the throttle and the boat moves 5-6mph and the revs sound way lower. Its hard to say how low without a tach but by sound it seems to be less than half the revs.
Could someone help me layout a game plan on where to go from here because I am lost now........could it still be the carbs? is it electrical? is there an issue in the foot? My mind is everywhere on this and I just need some help, please and thank you.......
1. The motor started life out as a 1997 Vmax 150. It somehow blew a hole in the #6 cylinder. Still not sure of cause. Motor was then given to my brother who put it on the boat.
2. A used powerhead was bought.--- this is an area that is grey to me. My brother was told that this used power head was the same block as the vmax. Upon me getting this boat to work on it I found out the two powerhead look the same but they had different carbs and different flywheel.
3. Used powerhead installed with the proper base gasket.
4. All components from the blown motor were swapped over to the used power head..ex.. carbs, heads, intake manifolds, all electronics, everything that could be swapped was. All new gaskets were used.
5. Carbs from blown engine rebuilt with kits. Each soaked in berryman carb cleaner bucket for 15-20min, flushed with water, ran 2 cycles in dishwasher, back for another 15-20 min soak in berryman, flushed with spray brake cleaner, all passages cleared with compressed air then alcohol flushed followed by final flush and spray of aerosol carb cleaner. All passages seemed to flow as needed. All jets, and other internal parts were done the same. Float height checked and all resembled per the manual.
6. 2 new fuel pumps installed
7. New fuel lines installed from boat to fuel pumps.
8. Fuel lines checked for tightness from fuel pumps to carbs. These lines seemed ok. They do not leak fuel anywhere.
9. Carbs linked and synced and all open together in unison.
10. The used powerhead did not have a pulser coil that could be advanced, the blown engine did so we swapped the blown engine pulser coil so it would work with the control arm and time with carbs. We used the used powerhead flywheel as the inside magnets looked the same as the blown engines flywheel. This was all set per the manual but I could look at this again.
11. New impeller water pump.
12. Ran some marine engine chemicals through the water passage to clean them very good. The thermostats and poppet valve are removed to allow full flow of water to the heads.This was done in short term to rule out any issues with thermostats.
13. I have checked the spark gap and its within range. As well as all the coil packs test out. But i could retest to confirm.
14. Oil injection system was removed. Oil level float was tapped up to mimic a full tank. All hoses and ports were capped.
15. Sometimes I do get an alarm, but do not know what it is from as I have no electronics on this motor yet. When the alarm sounds i can unplug both temp seniors and the alarm goes away. This makes me assume this alarm is only the water temp. It took about 30 min of testing last time before the alarm came on.
16. Compression test shows #110-#120 on all cylinders.
This thing seems to idle fine in Neutral, and will rev really high in Neutral. Place it into gear with no throttle and it wants to die, try to rev the throttle and the boat moves 5-6mph and the revs sound way lower. Its hard to say how low without a tach but by sound it seems to be less than half the revs.
Could someone help me layout a game plan on where to go from here because I am lost now........could it still be the carbs? is it electrical? is there an issue in the foot? My mind is everywhere on this and I just need some help, please and thank you.......