Downsides of imperfect impellers?

[Madcityami]

I bought my first boat about 2 weeks ago (‘10 SX210). RPMs were fine, but it just couldn’t get past low 30’s MPH. Based on reading lots of threads from this forum, I suspected an obstruction. Finally got it on a rack today, spotted something, and pulled my first pump. So the wear rings are pretty scratched and the impeller didn’t look great. Based on other threads, I assume most would tell me to replace them. But is performance my only gain? Are there any other considerations to replace now vs later?

 

[Babin Farms]

I would put it back together and see what it does without changing anything other than removing the stick. You could get through the season and have the impellers reworked or buy new ones if that's the route you want to take. It is all up to you on what to do, spend and repair.

 

[Madcityami]

Thanks for the response. I did happen to get it out on the water today. To my surprise, I didn’t notice much difference. Maybe my expectations are off because I’ve never driven a boat before this one. But it seems to work really hard and doesn’t really accelerate until I’m at 7 or 8k RPM. It just builds up a mountain of water behind the jets and then somewhere around 7 or 8k it starts to accelerate. Does this sound like I just need to replace the impellers or is this symptomatic of another problem? Thanks in advance for your wisdom.

 

[Babin Farms]

At 8k I’m up & going close to 30mph. Not much happening in the low rpm range Sounds like yours is good. What’s top speed?45-50? If close to that your fine.

 

[RXBoost]

I bought my 09 used last October and the impellers look MUCH better than that and I've been told to replace them. I can still hit high RPMs the way mine are, but possible cavitation is the symptom that I am having.

How do your intake grates look?

 

[BigAbe75]

My ‘11 SX210 had a top speed of about 38 in warm water. The new owner went out in cold water and got about 4-5 more mph out of it.

 

[Babin Farms]

My ‘11 SX210 had a top speed of about 38 in warm water. The new owner went out in cold water and got about 4-5 more mph out of it.

Interesting that temp affects it

 

[BigAbe75]

Interesting that temp affects it

Cooler water = cooler engine = higher rpms from what I understand. Not real sure. ?

 

[Babin Farms]

Maybe cooler air temp too? I can see where that would help.

 

[Madcityami]

I might hit 32MPH top speed. Water temp first time out was 70 and little warmer this most recent time out.

I don’t have pics of intakes, but they don’t look damaged or bent. After reading some other threads, I may look closer at the silicone job around them.

I do have wear on the keel like one of the previous owners beached it. That makes me assume the impellers saw their share of sand and rocks.

Maybe my newbie expectations are just off. Just didn’t feel right to hear the RPMs rev to 6000 and the boat doesn’t seem to be going any faster than no wake mode.

 

[RXBoost]

It certainly should be going faster than no wake mode at 6k rpm. I just replaced the intake grates on the starboard side as it was completely busted. I also re-siliconed both sides as it was super spotty. I haven't been able to go out since doing these things.

Let us know how it runs after re going the silicone, I'm anxious to see if it makes a difference. But imo your impellers should be replaced or refurbished.

 

[Babin Farms]

I might hit 32MPH top speed. Water temp first time out was 70 and little warmer this most recent time out.

I don’t have pics of intakes, but they don’t look damaged or bent. After reading some other threads, I may look closer at the silicone job around them.

I do have wear on the keel like one of the previous owners beached it. That makes me assume the impellers saw their share of sand and rocks.

Maybe my newbie expectations are just off. Just didn’t feel right to hear the RPMs rev to 6000 and the boat doesn’t seem to be going any faster than no wake mode.

Something is off of that’s all that you can gat out of it. Check silicone & if that’s good might have to get impellers repaired/replaced like @RXBoost suggested.

 

[Madcityami]

Thanks for the suggestions. I ordered up some 3M 4200 and I'll check for gaps next time I put it on the rack. I'm looking into options to get the impellers replaced as I'm assuming they are original.

Based on my 1st/3rd pictures above, the impeller duct (? part with the cone on it) looks to have been pelted with sand/stones and a little bumpy. Is that going to be a problem?

 

[RXBoost]

Thanks for the suggestions. I ordered up some 3M 4200 and I'll check for gaps next time I put it on the rack. I'm looking into options to get the impellers replaced as I'm assuming they are original.

Based on my 1st/3rd pictures above, the impeller duct (? part with the cone on it) looks to have been pelted with sand/stones and a little bumpy. Is that going to be a problem?

I think I looked on yamahasportsplaza for the impellers for my 09 and they were like $146 per side. I dont have an answer for you on the 2nd question.

 

[tdonoughue]

Jumping in late here... Those impellers are messed up enough to have that effect, I believe. I would pull the pump again and first take a pliers to the leading edge there. It should be straight (one of them is way bent in one spot on yours). Just even it out and make it straight like the other two. Then I would take a file and clean up that leading edge a bit. You don't want burs on that front edge. Then I would do the same thing on the sides that are against the housing.

The bend will not only cause cavitation, but also may throw your balance off at speed (as that part is going to pull more/less on the water depending on the bend direction). The burs and notches are going to cause cavitation. While cavitation will cause performance issues, note that it also causes damage. Cavitation causes little bubbles in the water when the impeller moves though it. Those bubbles are what cause poor performance (they are air--and the impeller doesn't move air well). But then as the impeller spins, those bubbles run against it and eventually pop. When they pop, they cause a 'rash' over time on the surface of the impeller and weaken it. So, replacing the impeller may be needed, but when I found mine were a bit chopped up (not as bad as yours, granted), I breathed new life into them with my file and my pliers as described.

The smooth path to the impeller is important for that same cavitation reason. If there are gaps or things hanging in the intake path (or immediately outside of it), then that causes turbulence in the water stream, which then makes for cavitation.

As for the scraping on the ring... Cleaning up your outside edge will help a little, but the burr there tells me you are definitely rubbing. That will cause some performance issues. Generally you see more of this when a boat is in salt. But eventually that ring corrodes and expands, impacting the impeller. And it scrapes. If it gets bad enough, you won't be able to start the boat. So that looks like it may be due for a replacement of the ring. Removing the burs from the impeller may buy you a little time, so you can tackle it in the off season.

 

[Madcityami]

Thanks for the feedback. I think you are right. I ran the engines for a bit on a work rack and can hear the pinging of the wear ring rub.

I decided to give an impeller change a try and ordered the impellers and housings. The housings are on backorder, so it will be a few weeks yet. I’ll update the thread with results.

I do have a impeller change related question. The service manual calls for gasket maker between the components. I didn’t think google would show so many options. Any recommendations?

 

[BrentEB]

oh yeah - definitely the impeller. Get the old one reconditioned and save as a spare after you change it out.

 

[tdonoughue]

@swatski might have a thought on the gasket maker...?

 

[Seadeals]

You can have the old impellers refurbished by a company like Impros. That will give you a backup set or a good set to sell that is a cheaper option for someone else than new. For comparison, @madyamaha we have identical boats mechanically, I hit between 40-43mph at WOT.

 

[BrentEB]

"I do have a impeller change related question. The service manual calls for gasket maker between the components. I didn’t think google would show so many options. Any recommendations?"

Do not use a hardening marine sealant between pieces unless you plan later posts being "they won't come apart". I used a silicone grease. The fitment is pretty tight.