Thrust Problems - Yamaha 212

[Cobra Jet Steering LLC]

With 2 engines . I would think it is just one , try each one separately and see if there is any big difference between the 2 especially the one with the bent impeller, Yamaha drive shafts do break on occasion and if something went into the pump that damaged the impeller it could break a shaft but there is something seriously wrong if the mechanic really did check the clean out plugs " because that would be the first thing I suspect that could do this to both engines" then you should look at the r p m's of the engines and see what those are turning . next just how bad are the pump liners what it the clearance between the impeller edges and the liners in 1000'ths of an inch, perhaps the previous owner drove it through a lot of rocks or sand and wore those out. I assume this is the same place that did your initial inspection. maybe you need a second opinion if they missed doing a test run. because the person who sold it knew what it was doing and just curious who did the maintenance on the boat when they had it because those people would surely have knowledge of what was wrong and why the boat was sold.

 

[84rzv500r]

the shafts break and the splines strip take a close look the splines too... impellers can wear out of tolerances... that looks like something was ingested did the engine stop abruptly? did you happen to notice any fine bubbles in the in the jet wash at idle? even with a junk stator my starboard pump still puts out thrust... it has nothing but cavitation below like 20 mph... but it works reasonable well over that until it falls over on the top end...

 

[Dan2poole]

Thanks for all the updates, the yahama guys who came out were marine mechanics and said they have been servicing the boat over the past few years.. Owner advises he took the boat out 2 weeks ago and everything was fine.

I did ask for a look at the plugs the other day and gave them a good pull and both were pretty secure.

I will look to give Low ball offer on the boat and deal with the fix once in my ownership.. (-$1000) Don't want to spend too much more on inspections and not purchase.

Many thanks for the repsonse

 

[Dan2poole]

Hi Guys,

So I was not having any luck with the yamaha mechanics. I think they were just guessing at possible problems.

Anyway, I decided to take a look at the impeller, shaft and housing myself.

On inspection, starboard plug was full of water from a recent wet test (with the mechanic, so surprised this wasn't picked up)

Also, the shaft and impeller seems in decent condition and no marks or scores on the housing.

This is making me think its the plugs or shaft spines slipping. I will look at changing the seals this week.

Attached a few photos so you guys can take a look.

Cheers
Dan

 

[84rzv500r]

ok it looks like you had an impeller strike so i would check the bearing housing on that side... do you see the crack in the shaft just behind the oring registration marks just aft of the input spline... also as others have said check the clearance between the impeller and the wear ring... i've seen cracked shafts take out bearings and take out the impeller clearance....

if you take a look in my build link i have a few example pics of where the problem could be...

 

[Dan2poole]

Hi guys,

Latest update on the cavitation,

The boat works if we start at 5000 revs then move to 6000 and so on, until it hits top speed.

We are unable to go from zero to top revs as it doesn't go anywhere, however if we work the revs gradually it works.

We have been told its because it is the 2010 model.

Any thoughts on this?

Thanks
Dan

 

[84rzv500r]

random thoughts... so if you had a 2009 or a 2011 model it wouldn't do that ? sorry about your luck? that's the dont giv-a-shit answer!!!

110,140,160,180 engines should all come out of the hole initially with very little cavitation, obviously lots of variables...

The boat should jump out of the hole like a shot if everything good... something wrong in the tunnels and/or the pumps.... bad pumps work kinda OK at speed but really suck out of the hole... ask me how I know LOL.... prolly feels a bit like a bad clutch or automatic trans... slips a lot till ya get moving but if you baby it once your going its ok >

Im coming up on a couple thousand hours of salt water operation in the last 6 years and I've broken/worn out every part of the jet pumps... twisted splines, snapped shafts, took out bearings, split nozzles, sheared the nozzles and buckets off, bused out the stator veins, bent impellers, bad mid bearings, leaky cleanout plugs, had to reseal the tunnels a couple times... had the transom plates come loose... shattered the jet tunnel bulkhead. I've used aftermarket and oem parts and developed a few of my own improvements, the first being the jet tunnel bulkhead that looked like and after thought and built by a 12 year old that didn't know the first thing about engineering and others around the stator housings and the nozzles...

I have two BAD setups on my boat right now, one missing half the stator veins but everything else ok and that side don't start working at all till 25 mph just cavitates and no thrust... the other side the pump is ok and the stator is ok but the mid bearing is sucking air... so that's all bubbly but gets me up on plane if i baby the throttles... its ok from 30-45 or so then it all falls apart as i get up around 9000 rpm and if I go WFO 10,500/7200 shaft RPM on the MR-1's the cavitation returns and I start slowing down... I am running the old pumps from the 135 two strokes that only turned 6700 shaft rpm...

Im building new hybrid HO pumps to solve the problems... a little bit of machine work , make some studs, plug a hole and weld some bungs in the the screen covers, problem solved for me...

you should be good with a "properly" functioning stock setup... My experience is that SOLAS impellers can reduce cavitation over stock but aren't as tough... you should be able to roll the throttles into WFO from no wake speed and jump on plane without any significant cavitation

 

[Scottintexas]

We have been told its because it is the 2010 model.

Any thoughts on this?

Thanks
Dan

Please tell us the name of the company that told you this so we will know never to recommend them to another member,

what a ridiculous answer, I hope you hear what they are telling you, we don't want to fix your boat, I wouldn't trust them ever again,

@84rzv500r
is this the crack you mentioned above ??


@Dan2poole can you confirm for us this is a crack and not just a surface scratch ?
not sure on your boat but my model requires two different pitched impellers, have you looked at the numbers on the impeller to confirm they are correct?

if the shaft is cracked I would certainly follow the path 84rz has mentioned,

Have you had someone accelerate the boat while you hold the cleanout hatch open and press the safety buttons down to see if you're getting a large amount of water past the cleanout plugs ? don't put your head directly over the cleanout plug holes !

I would also try to accelerate with only one engine (while the other is at idle) to see if you can notice a performance difference to narrow down which side to look at,

 

[Scottintexas]

sorry but just reading the whole thread again and seeing you are in Oman, that bent impeller blade could certainly cause your problem and as 84r said previously if the shaft is cracked you could have other issues,


.

 

[84rzv500r]

yep... here is another shaft like it but this one is mine LOL... some place I have one that completely failed..

Ive experienced 4 things that cause this with 20mm shafts... im going to 22mm OEM shafts in this build

• Aftermarket shafts
• Out of water experiences were you don't come off the throttle's soon enough
• impeller strike
• bad bearings...

 

[Cobra Jet Steering LLC]

As we have seen in the past , drive shafts break , usually starts as a slight crack and grows if you view the color of the broken part when it completely breaks in 2 you can see the oldest part of the fracture is darker and the newest is shiny.

 

[Dan2poole]

Please tell us the name of the company that told you this so we will know never to recommend them to another member,

what a ridiculous answer, I hope you hear what they are telling you, we don't want to fix your boat, I wouldn't trust them ever again,

@84rzv500r
is this the crack you mentioned above ??
View attachment 189733

@Dan2poole can you confirm for us this is a crack and not just a surface scratch ?
not sure on your boat but my model requires two different pitched impellers, have you looked at the numbers on the impeller to confirm they are correct?

if the shaft is cracked I would certainly follow the path 84rz has mentioned,

Have you had someone accelerate the boat while you hold the cleanout hatch open and press the safety buttons down to see if you're getting a large amount of water past the cleanout plugs ? don't put your head directly over the cleanout plug holes !

I would also try to accelerate with only one engine (while the other is at idle) to see if you can notice a performance difference to narrow down which side to look at,

Hey,

Thanks for the resp, so based on your post last week, I went out and polished the shaft to see if it was a crack. It turned out to be a surface scratch.

The seals on our clean out plugs don't look in the best condition so have purchased new. Should be arriving in the next day or so. I will install and open the hatch as you suggest.

Ill be honest, In oman the mechanics here tend to want to just replace all parts instead of proper diagnostics, so this forum has been great to bounce ideas off you guys as I am getting no luck from within country.

Cheers

 

[Dan2poole]

sorry but just reading the whole thread again and seeing you are in Oman, that bent impeller blade could certainly cause your problem and as 84r said previously if the shaft is cracked you could have other issues,


.

Next purchase will be new impellers as recommended by 84.

 

[Dan2poole]

random thoughts... so if you had a 2009 or a 2011 model it wouldn't do that ? sorry about your luck? that's the dont giv-a-shit answer!!!

110,140,160,180 engines should all come out of the hole initially with very little cavitation, obviously lots of variables...

The boat should jump out of the hole like a shot if everything good... something wrong in the tunnels and/or the pumps.... bad pumps work kinda OK at speed but really suck out of the hole... ask me how I know LOL.... prolly feels a bit like a bad clutch or automatic trans... slips a lot till ya get moving but if you baby it once your going its ok >

Im coming up on a couple thousand hours of salt water operation in the last 6 years and I've broken/worn out every part of the jet pumps... twisted splines, snapped shafts, took out bearings, split nozzles, sheared the nozzles and buckets off, bused out the stator veins, bent impellers, bad mid bearings, leaky cleanout plugs, had to reseal the tunnels a couple times... had the transom plates come loose... shattered the jet tunnel bulkhead. I've used aftermarket and oem parts and developed a few of my own improvements, the first being the jet tunnel bulkhead that looked like and after thought and built by a 12 year old that didn't know the first thing about engineering and others around the stator housings and the nozzles...

I have two BAD setups on my boat right now, one missing half the stator veins but everything else ok and that side don't start working at all till 25 mph just cavitates and no thrust... the other side the pump is ok and the stator is ok but the mid bearing is sucking air... so that's all bubbly but gets me up on plane if i baby the throttles... its ok from 30-45 or so then it all falls apart as i get up around 9000 rpm and if I go WFO 10,500/7200 shaft RPM on the MR-1's the cavitation returns and I start slowing down... I am running the old pumps from the 135 two strokes that only turned 6700 shaft rpm...

Im building new hybrid HO pumps to solve the problems... a little bit of machine work , make some studs, plug a hole and weld some bungs in the the screen covers, problem solved for me...

you should be good with a "properly" functioning stock setup... My experience is that SOLAS impellers can reduce cavitation over stock but aren't as tough... you should be able to roll the throttles into WFO from no wake speed and jump on plane without any significant cavitation

View attachment 189721View attachment 189722View attachment 189723View attachment 189724View attachment 189725View attachment 189726View attachment 189727View attachment 189728View attachment 189729View attachment 189730View attachment 189731View attachment 189732

Thanks for the detailed response!

I take your point on the model and year comment, probably not the most educated advice I have received LOL.

I don't suppose you can share your supplier name for the impellers? I will likely get them shipped over from the states anyway so would be good to use a reputable supplier that you guys are familiar with.

Thanks again

 

[Scottintexas]

Yamahasportsplaza or partspak, both oem parts, if not solas for aftermarket