WTF!!!!!

[Matt Phillips]

I'd definitely remove the tape before taking the boat in....ya don't want the dealer to see that regardless. I don't recall anyone every needing to put tape on the plugs to make them run/work better, so I'd think that removing the tape would the first thing.

As for water on top of the plugs, sometimes I do and sometimes I don't. More often I do have water on the plugs. If any wake boarding or surfing, it's a guarantee that there will be water on top of them. On Saturday we took the boat out to Emerald Bay (1 mile of no wake speed and then about 15 minutes of running each way) and at the end of the day, the top of the plugs was totally dry.

My thought is if it never jumped out of the water when you hit it, then something is definitely amiss. As said above, that thing should head out like a bat out of hell once ya hit it...

 

[Cobra Jet Steering LLC]

I bet there is something in a impeller between the blades where you can not see it from outside , you need to pull the pumps and check, the only other thing that comes to mind is really stale fuel will do this , as will overfilled oil

 

[John Mcpartland]

I'll pull the pumps tonight and take a look

 

[Cobra Jet Steering LLC]

just out of curiosity what r p m s are the engines hitting at w o t ?

 

[John Mcpartland]

just out of curiosity what r p m s are the engines hitting at w o t ?

About 7900

 

[Cobra Jet Steering LLC]

rpm with no thrust is cavitation it could be as simple as fishing line or a stick up between the impellers where you can not see it,, does either engine feel like it is trying harder to work than the other? if so look at the weakest one first

 

[BigN8]

Sounds like a clearance issue to me. I always cringed when I would rev my engines out of the water it sounded so horrific. The tolerence should be tight. Based on the pics you attached that did not look tight enough to me.

 

[Cobra Jet Steering LLC]

That is always another good possibility, use a feeler gauge and check the clearance between the end of the blades and the wear rings this could explain why both are doing the same thing if they are.

 

[John Mcpartland]

That is always another good possibility, use a feeler gauge and check the clearance between the end of the blades and the wear rings this could explain why both are doing the same thing if they are.

Do you know what it should be?

 

[Cobra Jet Steering LLC]

One more thing that is odd, when the liner swells and rubs on the impeller it just gets worse , especially when the pumps sit for an extended period of time and eventually they lock up the pumps. So if the pumps are cavitating then someone changed the pump liner sections but not the impellers. Not sure what Yamaha has for a clearance but I would think over 16thousands is getting there. What color are the pump liners? white or silver?

 

[Bruce]

Do you know what it should be?

Do you know what your pump's gap is?

This is the spec for an MR-1 I do not know the spec for the 1.8 but assume it to be similar if not the same.

 

[Cobra Jet Steering LLC]

Well there you have it 13 to 17 so I was pretty close with 16 like I said 16 is getting there.

 

[John Mcpartland]

Thanks. Can i do it from underneath through the grate or do i have to take the pump off?

 

[Bruce]

Thanks. Can i do it from underneath through the grate or do i have to take the pump off?

It looks like I checked with the nozzle removed. You might be able to get your hand in there.

https://jetboaters.net/threads/impeller-gap-010-good-or-bad.9484/

 

[John Mcpartland]

Well i did some measuring and both side maxed out my feeler gauge at .025. The starboard aide was a little more snug than the port side

 

[Bruce]

Well i did some measuring and both side maxed out my feeler gauge at .025. The starboard aide was a little more snug than the port side

That is outside of Yamaha’s limit.

 

[John Mcpartland]

What would cause them to be out of spec?

 

[GTBRMC]

What would cause them to be out of spec?

Wear ring oversized and/or out of round, impeller undersized and/or out of round, bent shaft, bearing issue...

...or a combo of two or more of above. Generally, Yamaha' s quality on this part of the boat has been very sound... as this system setup is critical to proper operation and problems out of the factory are quite rare (rarely heard of here).

 

[Bruce]

What would cause them to be out of spec?

Adding to the previous response running sand through the pumps.

 

[bronze_10]

Was this a new boat purchase... Or was it used?