MxRacer965
New member
Hello Everyone! Looking to try and help my father out with issues we've had with a 2004 model Honda BF9.9. It's on his 16' pontoon he bought a couple years ago. It's never really ran "right", and this Spring we had a local marine shop work on it to no avail so far. I'd rather just work on it ourselves at this point; but I could use some help in what direction to head.
Symptoms the past few Summers has been consistent RPM fluctuation when under way. We generally just use the pontoon for fishing and for slooooow cruising around the lake, around 1,600-1,800RPM is where we like to set it. Problem is it will hold that range for a few minutes, then start "running away" - revving 2K, 2.5K+ RPM, or it will drop down to near idle. I'll increase the throttle a little, only to have it speed up too much, then try to get the RPM back down to our desired range...repeat often...I'm constantly fiddling with the throttle lever fighting the motor speeding up and slowing down in RPM instead of staying steady.
2 weeks ago the shop replaced the fuel pump, and also wanted us to tilt the motor so far that the idle exhaust port was in the water! They claimed the exhaust wasn't exiting the prop correctly and caused cavitation, leading to the erratic operation. Sounded like a screw-ball idea to me. 2 years ago the carb and accelerator pump were rebuilt by the same shop. Last summer I replaced the fuel hose going from the tank to the motor.
Last weekend we had the boat put in the water and it ran around the lake fine on Saturday, but on Sunday we warmed it up, got under way, and within 50 yards it quit and refused to start. I towed it back to our dock with my Seadoo. Took starting ether to get it going again.
On Friday I did some testing...I started it up and let it idle. It idles fine in perpetuity it seems, around 1K RPM. I can also adjust the throttle while in neutral such that it runs at 3K RPM without issue....but as soon as I start to decrease the throttle nothing happens until I have moved it VERY VERY VERY slightly and the motor drops to 1K RPM again. There is ZERO way for me to get it to hold ANY RPM between 1K and 3K while in neutral.
It runs fine at wide open throttle, and it runs fine at idle, it just won't hold a steady RPM where we want to operate it. Any ideas would be appreciated!
Aaron
Symptoms the past few Summers has been consistent RPM fluctuation when under way. We generally just use the pontoon for fishing and for slooooow cruising around the lake, around 1,600-1,800RPM is where we like to set it. Problem is it will hold that range for a few minutes, then start "running away" - revving 2K, 2.5K+ RPM, or it will drop down to near idle. I'll increase the throttle a little, only to have it speed up too much, then try to get the RPM back down to our desired range...repeat often...I'm constantly fiddling with the throttle lever fighting the motor speeding up and slowing down in RPM instead of staying steady.
2 weeks ago the shop replaced the fuel pump, and also wanted us to tilt the motor so far that the idle exhaust port was in the water! They claimed the exhaust wasn't exiting the prop correctly and caused cavitation, leading to the erratic operation. Sounded like a screw-ball idea to me. 2 years ago the carb and accelerator pump were rebuilt by the same shop. Last summer I replaced the fuel hose going from the tank to the motor.
Last weekend we had the boat put in the water and it ran around the lake fine on Saturday, but on Sunday we warmed it up, got under way, and within 50 yards it quit and refused to start. I towed it back to our dock with my Seadoo. Took starting ether to get it going again.
On Friday I did some testing...I started it up and let it idle. It idles fine in perpetuity it seems, around 1K RPM. I can also adjust the throttle while in neutral such that it runs at 3K RPM without issue....but as soon as I start to decrease the throttle nothing happens until I have moved it VERY VERY VERY slightly and the motor drops to 1K RPM again. There is ZERO way for me to get it to hold ANY RPM between 1K and 3K while in neutral.
It runs fine at wide open throttle, and it runs fine at idle, it just won't hold a steady RPM where we want to operate it. Any ideas would be appreciated!
Aaron