2015 mercurforty hp jet issue

[mark2052]

My 2915 40 h0 mercury jet runs fine to 4000 rpm any thing over that results in no forward progress. The tac goes to 6,000 rpm and the boat stops moving. Go back to 4,000 rpms or lower the boat has thrust again. help

 

[FuzzyGrub]

I am assuming it use to go faster without this issue vs a new set-up. Sounds like you are cavitating. Check the foot grates, make sure they are all straight and clear of any debris. Check your wear liner to impeller gap. Adjust shims if out of spec. If deep gouges in liner, consider replacing. Sharpen impeller. All "how to" can be found on OutBoardJets

Can also be caused by damage or protrusions on/near the centerline of the boat.

PS: Welcome to TinBoats!

 

[mark2052]

I am assuming it use to go faster without this issue vs a new set-up. Sounds like you are cavitating. Check the foot grates, make sure they are all straight and clear of any debris. Check your wear liner to impeller gap. Adjust shims if out of spec. If deep gouges in liner, consider replacing. Sharpen impeller. All "how to" can be found on OutBoardJets

Can also be caused by damage or protrusions on/near the centerline of the boat.

PS: Welcome to TinBoats!

 

[mark2052]

Thanks for the info. changed the impeller and and liner. Set the clearence to .032 will double check to make sure its correcxt..

 

[FuzzyGrub]

Thanks for the info. changed the impeller and and liner. Set the clearence to .032 will double check to make sure its correcxt..

I think that is a maximum number, ie if it exceeds, move a shim. With a new liner and impeller, I’d expect a tighter gap. I don’t know what the minimum should be, though. The closer to that minimum, the better the performance.

I think there is some play in the liner and it should be centered to the impeller, as best as possible. Same/sim gap all around.

Did you have the issue before changing liner and impeller?

 

[mark2052]

Sorry for keeping you guys waiting. The weather has been cold in the Poconos this week. I rechecked every thing and found the gate not fully locking all the way down. I adjusted the cable to a full lock in the down position. Went 9on the water today and everthing worked fine for 20 minuets or so. All of a sudden I started to lose speed with the rpms at a constant 4,900. Lifted the motor checked the gate and it moved back to the 3/4 position. Worked the cable back and forth a few times and the gate went back to the fully locked position. Ran fine the rest of the day. I am going to replace the cable myself. I will take the motor over to the Mercury dealet to run a scan on the motor to see if he can get the rpms back to 5,200. Once again thanks for the input.