Port impeller sits proud

[Bruce]

I am in the process of changing impellers. I decided to pull the pump housing and gently fit them into it instead of possibly letting the scrape as I reassembled the pump to the boat .

@Rana noticed that the port impeller leading edges sit slightly beyond the outer of the pump housing. I compared to the starboard pump and found its impeller leading edges are around half an inch inside the pump housing.

I installed the factory starboard impeller in the port pump and found it sat fully inside the housing as it would on the starboard side. I also reinstalled the factory port impeller and found it sat with the leading edges proud of the pump housing. The issue (feature) must be related to the thread on the 6P600 impellers.

All of the impellers are Yamaha impellers with factory part numbers stamped into them.

Has anyone else noticed this? Is an explanation out there?

Here is a picture showing the difference. The port pump is on the right.

 

[Noko]

It could be to offset the torque. I believe the port impeller is pitched differently than the starboard. With the port impeller a little forward you have a longer moment arm that may help offset the torque. Just a guess.

 

[swatski]

I am in the process of changing impellers. I decided to pull the pump housing and gently fit them into it instead of possibly letting the scrape as I reassembled the pump to the boat .

@Rana noticed that the port impeller leading edges sit slightly beyond the outer of the pump housing. I compared to the starboard pump and found its impeller leading edges are around half an inch inside the pump housing.

I installed the factory starboard impeller in the port pump and found it sat fully inside the housing as it would on the starboard side. I also reinstalled the factory port impeller and found it sat with the leading edges proud of the pump housing. The issue (feature) must be related to the thread on the 6P600 impellers.

All of the impellers are Yamaha impellers with factory part numbers stamped into them.

Has anyone else noticed this? Is an explanation out there?

Here is a picture showing the difference. The port pump is on the right.

View attachment 57935

Yeah, this is strange.
What's the difference in pitch on the leading edge? If you have the data handy.

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[swatski]

I can not find what it is for your boat right now, the difference can be couple degrees, so pretty substantial.
Port is pitched more aggressively but I always thought this was more of a trailing edge thing. Maybe not.
Do you still have those out? Wonder what the leading edge difference looks like when those sit side by side:

Here is one table I could find

 

[Noko]

I am in the process of changing impellers. I decided to pull the pump housing and gently fit them into it instead of possibly letting the scrape as I reassembled the pump to the boat .

Have you put the pumps back together and see how they fit? I would say @swatski is probably a good source on the pumps.

 

[buckbuck]

.

 

[KXCam22]

Is the dimension of the impeller the same. Perhaps the height of the impeller is larger to accommodate the pitch. Cam

 

[Bruce]

@swatski, @KXCam22 the manual documents the pitch of the impellers as Port 18.1° / Starboard 15.1°.

I reassembled the pumps with the new impellers last night. If the weather cooperates we will test them out today.

 

[swatski]

@swatski, @KXCam22 the manual documents the pitch of the impellers as Port 18.1° / Starboard 15.1°.

I reassembled the pumps with the new impellers last night. If the weather cooperates we will test them out today.

Right, that's trailing edge and what you question is leading edges. I'm just surprised it is that much of a difference - I love it! Yamaha used to pay attention to mechanical detail.

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[Bruce]

The storms kept us in today so the test run will be later in the week.

Interestingly Yamaha had drilled the new impellers for I assume balance. They had made in Taiwan stickers. I wonder whose factory that might be.

 

[Bruce]

Setting the factory impellers side by side this appears to explain it

 

[Seadeals]

For reference, I checked my '06 SX210 and the leading edge of both impellers is right at the forward edge of the wear ring section (identical to your port pump).

 

[swatski]

Setting the factory impellers side by side this appears to explain it

View attachment 57971

I wish they were doing it in the new boats. Must be cost cutting.

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[Speedling]

I wish they were doing it in the new boats. Must be cost cutting.

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Talking about the curve on it?

 

[swatski]

Talking about the curve on it?

No, just pitching the port and strbd differently to account for differences in intake efficiency.
The new boats have both impellers pitched the same. They claim it is because of the keel you don't need it, blah, blah. But it is not true. Obviously just cutting cost.

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[Speedling]

No, just pitching the port and strbd differently to account for differences in intake efficiency.
The new boats have both impellers pitched the same. They claim it is because of the keel you don't need it, blah, blah. But it is not true. Obviously just cutting cost.

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I hear ya, yeah, the pitching different is due to pump loading characteristics. A keel doesn't negate it just negates one of the effects it can cause.

 

[buckbuck]

Definitely a difference on those in my boat.

 

[mark_m]

Bruce,

Did you notice improvement with the replacement impellers?