Boat wont go over 18 MPH

[portlandbucfan]

Hi,

I just had my boat "summarized" by a dealer. I took it out today for the first time this year and the boat would rev all the way up but wouldnt go past roughly 18MPH.


Initial thoughts:
Dealer put in wrong plugs?
Bad gas/running off the fuel stablizer?

Any ideas?

First time having the dealer do this, years past I have done it all myself.

 

[steveinmd]

If its revving to max and not going fast, I would lean toward the clean out plug not installed

 

[portlandbucfan]

If its revving to max and not going fast, I would lean toward the clean out plug not installed

Thank you, didnt think of that. If its loose it can cause boats to not get up to speed? Never had that issue so would add that to my checklist.

 

[steveinmd]

Thank you, didnt think of that. If its loose it can cause boats to not get up to speed? Never had that issue so would add that to my checklist.

Most definitely. The engine will Rev freely and there is usually more noise and vibration.

 

[portlandbucfan]

Any other ideas? I took it out on water today and still had issue. Clean-Out port was locked and tight.

In reading on site, might be improperly/bad installed spark plugs?

 

[Acard7]

If your clean out plug was locked in place properly then I’d almost guess something is lodged in your impeller. Any vibration at all while trying to get up to speed? Are your RPMs maxing out at wide open throttle? Or is it only reaching 3-4k RPMs? I’d also check your air filter and oil level, too much oil may make it run awful.

 

[portlandbucfan]

If your clean out plug was locked in place properly then I’d almost guess something is lodged in your impeller. Any vibration at all while trying to get up to speed? Are your RPMs maxing out at wide open throttle? Or is it only reaching 3-4k RPMs? I’d also check your air filter and oil level, too much oil may make it run awful.

No vibration and nothing lodged in that I could see. It maxes out at wide open throttle. Its frustrating since I have done all the servicing in the past. This year I havent had time so I took it to the dealer.

 

[TeenGee]

Is the bucket partially closed and not fully opening?

 

[portlandbucfan]

Is the bucket partially closed and not fully opening?

Bucket looks to be opening

 

[Acard7]

This is head scratching… I put a whole can of seafoam and stabilizer in while winterizing, also fog the cylinders/intake, and it still starts and runs fine when I “summerize,” so I can’t imagine any of that is your issue. I’d pull the boat out, take the plug out and feel around, then get underneath and look up through the intake at the shaft and impeller to rule out anything there. Make sure your oil is proper level and air filter isn’t soaked. Then i would change the spark plugs to rule out a fouled plug. Other than that i have no clue as to why you’re not reaching greater speeds!

 

[portlandbucfan]

This is head scratching… I put a whole can of seafoam and stabilizer in while winterizing, also fog the cylinders/intake, and it still starts and runs fine when I “summerize,” so I can’t imagine any of that is your issue. I’d pull the boat out, take the plug out and feel around, then get underneath and look up through the intake at the shaft and impeller to rule out anything there. Make sure your oil is proper level and air filter isn’t soaked. Then i would change the spark plugs to rule out a fouled plug. Other than that i have no clue as to why you’re not reaching greater speeds!

Appreciate it. I put stablizer and blast engine dry and store it in my garage every winter. I'm taking it back to the dealer to have them figure it out. They said they switched out oil, did plugs, etc.

 

[Neutron]

If your rpms are going to normal levels and there is no speed increase then its a problem within the pump/impeller not in your engine.
If it was only going 18mph and it was reving only say 6k rpms then i would say its engine related, like a supercharger clutch blew up.
If your rpms are going over 7500, its pump related.

 

[portlandbucfan]

If your rpms are going to normal levels and there is no speed increase then its a problem within the pump/impeller not in your engine.
If it was only going 18mph and it was reving only say 6k rpms then i would say its engine related, like a supercharger clutch blew up.
If your rpms are going over 7500, its pump related.

Thank you. Just timing seems odd. First time out for the year after the summarization and 20 feet from dock noticed the issue. Ran completly fine last year.

 

[steveinmd]

I agree with what the others are saying. If you are getting max revs, then it is pump/clean out related and not the engine. I've seen where it was something as simple as fishing line wrapped around the impeller shaft that caused enough cavitation that it killed the speed.

These are direct drive units. If you're getting 7500rpm at the motor, you're getting 7500 at the pump but not moving the required water to get up to speed. So either you're not pulling in enough water (front side of impeller) or you have a pressure problem on the rear side of the impeller.

 

[drewkaree]

... nothing lodged in that I could see.

20 feet from the dock, and it's noticeable. The first suggestion of the cleanout port would be the first thing to verify, and you said you did that.

The impeller is longer/deeper than just what can be seen. First time out, hasn't been run since last year/fall season, and you put in when lots of runoff would wash debris into the water.

Pull your pump. Ruling out the cleanout plug leaves something in the pump that's not visible. Could be lodged in the second turn of the impeller out of eyesight, but it can't hide when it's removed.

Wrong plugs shouldn't be detrimental to the extent that it robs you of 25mph, and all other indicators you've relayed to us point to pump issues.

 

[TeenGee]

A leaking clean out plug port could cause cavitation. At slow speed the dynamic pressure is not high enough to overcome the suction of the pump and if the clean out plug is not fully sealed, the pump will suck air past the plug and cavitate.
Fill the port with water and accelerate slowly. If the problem still exists and the port is still full of water, the plug is not incriminated.
If the problem goes away, try a hole shot.
If the hole shot is good. Drain the water from the port and hole shot again.
If problem recurs inspect the seal on the plug and where it seats in the port. If you don't see anything, try this: https://jetboaters.net/threads/another-clean-out-plug-thread.43036/ start with post #19.
Good luck.

 

[sunbyrned]

I think @drewkaree ’s suggestion of pulling the pumps is spot on. What you’re describing has happened to me a few times. Even if I can’t visually find debris, once I pull the pumps and reinstall them, the problem goes away. Here’s a video on how to do it on older boats like mine.