Engine bogs down after half throttle

[97sportser]

97 sportster

I was out on the water and ran through some really stringy sea weed and immediately the boat lost top end power. I drove back to the dock and flushed the boat when I got home with no issues. Nothing was stuck in the impeller or pump. I took the boat back out the next day to pull the kids on a tube and did not have any power. Then the overheating warning buzzer went off. I got home and flushed the boat with no issues or obstructions. I noticed that with the boat hooked up to the hose, that it will rev to half throttle very quickly but then any further throttle, the engine just bogs down at the same RPM. I have done the following to no avail.

1 - Removed the muffler and didn't find anything inside
2 - Checked the in-line fuel filter and it was full of crap so I cleaned it.
3 - Removed the very small fuel filter from inside the carb and it was clean (like new)
4 - Removed both jets from carb and both were clear and clean
5 - Removed the baffle from the gas tank and it was clean
6 - checked carb valve action and both are in sync.
7 - Replaced the spark plugs with NGK's
8 - The new plugs were wet with oil and gas when I pulled them back out after running, so I adjusted the carbs to run a little more lean.

Engine still bogs down after half throttle!! Please Help.

 

[Dr Honda]

does it bog and try to stall, or does it just not go past 3500 rpm's?

 

[97sportsers]

New name

I had to create a new online name, 97sportster was locked out from posting or replying......

To answer your question, it runs great at half throttle, when at full throttle, it still runs great, just at half throttle RPMs. When I pull the choke at full throttle, the engine dies. Not sure what that means.

The last time I had it out on the water, trying to diagnose the issue, at full throttle the boat would speed up a little then slow down, then speed up and slow down on a 10 second interval. Not a big change, but noticeable.

 

[97sportsers]

Dr Honda

Dr Honda I found the following reply on another thread. How do you know what RPM the boat is at, I only have a gas guage.

"Is the rev limiter kicking in right at 3500 RPM?
If it is... the neutral switch on the shift lever is stuck."

 

[seadooya]

think you should be able to tell betwenn 3500 or 7k rpm. Pull the pump off, and inspectthe wearring and impellor. Also, disconnect your waterlines from pump and motor, and shoot air thru them. If the wearring looks beat, think it may be your problem, because your reaching wot at only half throttle, then your hitt'n rev limiter, anything past it.

 

[97sportsers]

Took the boat out today and everything was great except the engine would pulse at full throttle. (Make and loose power). I noticed, that when I gave it full power from a stand still, it performed fine, got right up on plane, but once I got up on plane then it would imminently start the pulsing, making power for 5 seconds then loosing power for 5, then back on again. It felt like someone was turning the gas on and off or it was not getting enough air. When I backed the throttle down to 3/4 the boat ran fine, I could pull my wife on the tube and fly around the water. Any ideas?

 

[Dr Honda]

Either your fuel select valve is leaking, or the carbs just need to be gone through again.


I know you said that you pulled the jets, and checked them... but did you verify the pop-off pressure? Did you blow though the passages in the carb with cleaner, and compressed air?

One thing you can do, is to set the fuel select valve to "Reserve" to see if that helps out. But... I wouldn't keep running the boat the way it is. It sounds like it's going lean, and 2-stroke engines don't like that since less fuel also means less oil.

 

[seadooya]

Took the boat out today and everything was great except the engine would pulse at full throttle. (Make and loose power). I noticed, that when I gave it full power from a stand still, it performed fine, got right up on plane, but once I got up on plane then it would imminently start the pulsing, making power for 5 seconds then loosing power for 5, then back on again. It felt like someone was turning the gas on and off or it was not getting enough air. When I backed the throttle down to 3/4 the boat ran fine, I could pull my wife on the tube and fly around the water. Any ideas?

i'd think, you got a rectifier going south on you

 

[Dr Honda]

i'd think, you got a rectifier going south on you

:agree:


Yup... check that too.