Hi All-
I hope the mods (or anyone really) don't mind me starting a new topic for this. I initially started a thread (now buried on page 3 with no responses) regarding this, but I have quite a bit of new information. So hopefully I can get some good traction and maybe get to the bottom of this.
There are multiple symptoms that feel to me like they may be caused by the same problem. The most obvious symptom is the tachometer giving a reading that seems to be ~ 2x the actual motor RPM. The engine cranks right up and idles very nicely. My handheld tach reads about 650 RPM at idle, but tach gauge reads about 1,00 - 1200. As throttle increases, tach seems to maintain the x2 pattern and quickly the guage is getting close to 4k - 5k rpm. I am VERY certain the motor is not actually turning this fast. I've really only done this once or twice, as I know it's quite bad to rev the motor while not under load. This RPM issue is present whether the prop is engaged or disengaged.
The second symptom is that when engaged and running, it really stumbles and maybe misfires or something and it just can't get much past 1500 RPM (tach reads closer to 3k rpm). I know it's not turning at 3k RPM, because when the motor was running correctly, 3k RPM was quite a bit faster.
So here's what I've tested or done so far:
1. Check for spun HUB - marked prop, ran boat, checked marks .. all still lined up. Of course since RPM issue is present when not engaged, this was probably not productive.
2. Clean the oil flow sensor and filter screen. It did have stuff in it, but didn't seem like enough to put it into limp mode.
3. Bleed the oil pump multiple times, ensure proper oil in the oil tank, use syringe to fill oil pump and oil lines.
4. Check all in-line oil check valves.
5. Finally I removed the oil pump all together and dissassembled it and cleaned all the obvious passages. Re-install, bleed the pump, no change in behavior.
6. Check spark on all cylinders (did with an in-line light type tester). Did not check strength of spark or ability to jump particular gap. Definitely have some spark at all cylinders.
7. Compression check .. very consistent 90psi on all 6 cylinders. Seems like a low number to me, but it's very consistent.
8. Disconnected oil level indicator and disconnected oil flow sensor .. ran motor with no change.
9. About 8 months ago I had the carbs professionally cleaned and I installed rebuild kits on them. At the same time I removed the oil pump, I removed the carbs and gave them a good cleaning, even though they all still looked very clean.
I'm really at a loss now. Someone has suggested to me to check the coil counter at the flywheel. I am wondering if I should also check my throttle position sensor. I don't know the correct procedure for that, but did measure a consistent resistance on it. The shop manual has a set of calculations to conduct on it, but it required the TPS to be on the motor with power supplied. There were some voltage / ohm calcs it wanted me to perform, but since I didn't have the TPS installed at the time, couldn't take the readings. I did however measure resistance with the TPS off. I don't know itf it's meaningful or not, but I got a reading of 9.7 kohm fully closed and 4.1 fully opened, with a smooth transitions between the two.
So that's about it .. I'm not sure where to go from here. Someone has suggested I look at the coil counter and see if that's reading correctly.
Anyone else got any ideas? I'm running out of stuff I know how to look at!
Chris
I hope the mods (or anyone really) don't mind me starting a new topic for this. I initially started a thread (now buried on page 3 with no responses) regarding this, but I have quite a bit of new information. So hopefully I can get some good traction and maybe get to the bottom of this.
There are multiple symptoms that feel to me like they may be caused by the same problem. The most obvious symptom is the tachometer giving a reading that seems to be ~ 2x the actual motor RPM. The engine cranks right up and idles very nicely. My handheld tach reads about 650 RPM at idle, but tach gauge reads about 1,00 - 1200. As throttle increases, tach seems to maintain the x2 pattern and quickly the guage is getting close to 4k - 5k rpm. I am VERY certain the motor is not actually turning this fast. I've really only done this once or twice, as I know it's quite bad to rev the motor while not under load. This RPM issue is present whether the prop is engaged or disengaged.
The second symptom is that when engaged and running, it really stumbles and maybe misfires or something and it just can't get much past 1500 RPM (tach reads closer to 3k rpm). I know it's not turning at 3k RPM, because when the motor was running correctly, 3k RPM was quite a bit faster.
So here's what I've tested or done so far:
1. Check for spun HUB - marked prop, ran boat, checked marks .. all still lined up. Of course since RPM issue is present when not engaged, this was probably not productive.
2. Clean the oil flow sensor and filter screen. It did have stuff in it, but didn't seem like enough to put it into limp mode.
3. Bleed the oil pump multiple times, ensure proper oil in the oil tank, use syringe to fill oil pump and oil lines.
4. Check all in-line oil check valves.
5. Finally I removed the oil pump all together and dissassembled it and cleaned all the obvious passages. Re-install, bleed the pump, no change in behavior.
6. Check spark on all cylinders (did with an in-line light type tester). Did not check strength of spark or ability to jump particular gap. Definitely have some spark at all cylinders.
7. Compression check .. very consistent 90psi on all 6 cylinders. Seems like a low number to me, but it's very consistent.
8. Disconnected oil level indicator and disconnected oil flow sensor .. ran motor with no change.
9. About 8 months ago I had the carbs professionally cleaned and I installed rebuild kits on them. At the same time I removed the oil pump, I removed the carbs and gave them a good cleaning, even though they all still looked very clean.
I'm really at a loss now. Someone has suggested to me to check the coil counter at the flywheel. I am wondering if I should also check my throttle position sensor. I don't know the correct procedure for that, but did measure a consistent resistance on it. The shop manual has a set of calculations to conduct on it, but it required the TPS to be on the motor with power supplied. There were some voltage / ohm calcs it wanted me to perform, but since I didn't have the TPS installed at the time, couldn't take the readings. I did however measure resistance with the TPS off. I don't know itf it's meaningful or not, but I got a reading of 9.7 kohm fully closed and 4.1 fully opened, with a smooth transitions between the two.
So that's about it .. I'm not sure where to go from here. Someone has suggested I look at the coil counter and see if that's reading correctly.
Anyone else got any ideas? I'm running out of stuff I know how to look at!
Chris
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