Impeller issues - trashed bearing - pump rebuild & impeller swap

[swatski]

This is fantastic!

It's like jet pump porn. lol

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[Sbrown]

This is fantastic!

It's like jet pump porn. lol

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I'll say! Can't wait to hear how his boat performs!

 

[Scottie]

Got back to the lake this afternoon, shafts went in with no issues, bolted everything up and ran it on the hose to test. Nothing exploded! Had a slight bump on both motors, but I expected that as the delrin wear rings were tight in a couple spots on the impellers. Dropped her in the water and babied her for a bit, and everything smoothed out. The noise reduction is incredible. I would talk about how she is out of the hole, but someone took the hole! Seriously, I can't find it. ZERO cavitation, very quick. Finally pegged it, and hit 7800 rpms (previously never over 7400), and hit 50.5 mph, on a short run, with the Bimini up! I think I could get 52 or better with top down and a longer run. I've never seen higher than 49.8 on the boat. I didn't have the boat brand new, so I don't know what it might've done then, but this is a different boat than what I had. It's SOOOO much quieter, and SOOOO much smoother. It's quicker, and faster. I'm ecstatic.

 

[Seadeals]

Great news! Awesome of you to share everything along the way too. I am not hoping to do this anytime soon; but if I ever do, it will not be a problem thanks to you. I am curious about the sound comment. Do you mean less rattling etcetera at lower rpm or are you saying it doesn’t make as much noise at 7800? At that speed/rpm, I figure 99.9% of noise is engines (aside from wind) and has little to do with impellers or bearings.

 

[Scottie]

I am curious about the sound comment. Do you mean less rattling etcetera at lower rpm or are you saying it doesn’t make as much noise at 7800? At that speed/rpm, I figure 99.9% of noise is engines (aside from wind) and has little to do with impellers or bearings.

You're absolutely right. I meant from idle to 27 or 28mph. 0 to 5500 rpm, which is what I run if we're "cruising". Past that, I agree with you, nothing would make much difference, and no one is really talking anyway. I would characterize the boat as very quiet at idle, and "easy to talk" at 5500 rpm. I have done some basic soundproofing, and had planned to do more, but I don't believe I need to now. I would say the difference is at least equal to the difference made when adding a good engine hatch seal. Keep in mind my boat is a 2013, so I don't have any of the "quiet cruise" enhancements on the newer boats, so you may or may not see the same improvements in newer models.

 

[swatski]

I am curious about the sound comment.

That's the beauty of those delrin inserts, I've been saying this for a while. One of the major components of Yamaha noise is due to the the wear ring - the entire drive is above water on plane, and the sound of impelelr coming in contact with the wear ring reverberates. The delrin insert takes it away. It does not quiet the engine noise itself, but the overall NVH reduction is very notable. My experience is with 190 which are silly loud.

As far as the performance - impellers literally curve a groove in those plastic rings so those are super tight, much tighter wthan the factory specs without the noise, and that means the performance is up and cavitation is gone.

Awesome results, thank you for sharing!!!!

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[Beachbummer]

Let me share the counterpoint coming from Sea Doo... Those rings self destruct if you look at them funny. I'd change 2 or 3 a season. I was happy to see how sturdy the stainless rings are on the yamaha's.

Maybe you guys are careful and have no issues with them. I really like the durability and don't mind the noise of the stainless... But now with these housings you can have your cake and eat it too. You get the plastic ring you like, and I keep the stainless

Great to hear the cavitation is greatly reduced, that is excellent news.

 

[Scottie]

Those rings self destruct if you look at them funny. I'd change 2 or 3 a season. I was happy to see how sturdy the stainless rings are on the yamaha's.

Good point! Two sides to every coin as they say. No salt for me, and we don't beach the boat or hang out over the gravel beds or anything, so I'm hoping for much more durability than that! Luckily they are easy/cheap to change, but if it turns out to be anything like 2 or 3 a season, I'd likely be headed back to stainless. Given the benefits I've observed so far, I would be ok changing them every winter, but 2 or 3 seasons would be great if course. I guess I'll find out!

As for the performance improvements, I didn't feel like I suffered from a lot of cavitation before, and didn't have anything to "fix" had there not been a failure. With that said, there's definitely been an improvement. I wish there was a way to quantify how much improvement is from the 6CW impellers, and how much is from new parts with tighter tolerances, including the delrin liners. I believe both are contributing. I do find it very interesting that I'm actually reaching HIGHER rpms than before. I expected the opposite there honestly. The 6CW should be "harder" to turn, in theory, right?

I am also going to be adjusting the L13 spacers. I put it back together with 3 spacers (blue, red, gold) on the port side, which is how I had it before. What was about a 100 rpm deficiency for the port side, is now about 400. I can't decide if I'm going to remove spacers from the port side or add to the starboard side. Right now the starboard side has none, so I'll probably start by adding the thick one there and see what happens.

 

[swatski]

@Scottie This thread is like a gold mine.

It just reminded me looking at your 6CW vs 6AP pic, weird pitch difference.
The 6CW (red) is a touch more aggressive than 6AP for STRBD (green) but much less aggressive than 6AP for PORT (blue).
(table courtesy of Jerry Gaddis)


So the magic of the 6CW could be the pitch but also perhaps it's slightly longer blades (the blades overlap to the same extend - seem like the exact same length, but the 6CW may be a bit taller as compared to 6AP - on the leading edge, not affecting the shaft fitment).

Still does not explain higher RPM of course, but that could be the new bearings, too.

I'm also struck by your L13 spacer effects - in my experience the L13 works way better with the 6CW as compared to any other impeller including Skats and Solas. Now that you have the plastic ring removing any remnants of cavitation, may want to play with the spacers - you want those to dial the WOT RPM of each pump to be just under the rev limiter by about 100-150 RPM.

Either way, your results are the bottom line - and the data is fantastic.

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[Scottie]

Nice! So that explains the port side rpm difference. Since stock impellers were pitched differently, and my new 6CWs are the same, then engine rpms should be closer together. Since I installed the same spacers to compensate for an rpm difference that is no longer there, the difference is actually greater.

 

[swatski]

Since stock impellers were pitched differently

For your boat stock impellers were the same from factory, unless you or PO changed something. They were pitching the 230/232 and pre-AK 240/242s different for both sides. If that makes sense.

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[Scottie]

Interesting. So the tach goes to 8k. Is that the redline also? I've never hit it obviously.

 

[swatski]

Interesting. So the tach goes to 8k. Is that the redline also? I've never hit it obviously.

I think most would consider 7,700 - 7,800 RPM to be the best "target". Yamaha does not publish power/torque curves but my understanding is that you hit the law of diminishing returns beyond that.

Here is the rev limiter table for your 1.8:



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[Scottie]

Awesome! Thank you. In that case, I'm right there already. 7800 or so yesterday. More tests today and I'll pay more attention to the rpm.

 

[swatski]

Awesome! Thank you. In that case, I'm right there already. 7800 or so yesterday. More tests today and I'll pay more attention to the rpm.

I know. That's why you are breaking 50! with no cavitation and great hole shot - that is just perfect.

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[InmyElement]

Wow, great write up! Thank You!
I've read every post I can find about changing the impeller and bearings. All of you convinced me that this will be my spring project. Changing out Impeller, wear ring and oil bath/inspect the bearings. Did all of you go with the 6CW and the delrin inserts? I've been shopping around..where is the best place to purchase everything?
Thanks

 

[Cobra Jet Steering LLC]

I buy my pump parts including the plastic liners and pump housing, motor mounts, cables, intermediate bearings, etc locally at www.sbtontheweb I have several hundred hours on my plastic liners, no clanging and no cavitation.

 

[Gwade8808]

All parts have been ordered. Going with 6CW impellers and delrin wear rings. Impellers arrived today.
View attachment 99396

Where did you order from? Doing the same job on a 2015 limited S and can't find the 6AP OEM impeller. Saying 20ndays back order everywhere.

 

[Gwade8808]

@Scottie This thread is like a gold mine.

It just reminded me looking at your 6CW vs 6AP pic, weird pitch difference.
The 6CW (red) is a touch more aggressive than 6AP for STRBD (green) but much less aggressive than 6AP for PORT (blue).
(table courtesy of Jerry Gaddis)
View attachment 101066

So the magic of the 6CW could be the pitch but also perhaps it's slightly longer blades (the blades overlap to the same extend - seem like the exact same length, but the 6CW may be a bit taller as compared to 6AP - on the leading edge, not affecting the shaft fitment).

Still does not explain higher RPM of course, but that could be the new bearings, too.

I'm also struck by your L13 spacer effects - in my experience the L13 works way better with the 6CW as compared to any other impeller including Skats and Solas. Now that you have the plastic ring removing any remnants of cavitation, may want to play with the spacers - you want those to dial the WOT RPM of each pump to be just under the rev limiter by about 100-150 RPM.

Either way, your results are the bottom line - and the data is fantastic.

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Does going with the 6cw require a different model/size wear ring? 6CW shows it's for a 190 series boat. I have the 6AP for a 2015 242 limited s but they are a 20 day back order. The 6cw is in stock and only a .3 difference in pitch. Just didn't know if tolerance is the same and only a slight pitch difference or if I would need different wear rings as well?

 

[Gwade8808]

Does going with the 6cw require a different model/size wear ring? 6CW shows it's for a 190 series boat. I have the 6AP for a 2015 242 limited s but they are a 20 day back order. The 6cw is in stock and only a .3 difference in pitch. Just didn't know if tolerance is the same and only a slight pitch difference or if I would need different wear rings as well?

Wow lol disregard.. I'm an idiot.. the chart clearly states they are all 154.6mm.. 6CW's it is!!