1998 Yamaha 25Hp 2 cylinder 2 stroke oil mix outboard making squeal noise just below

[grf00]

1998 Yamaha 25Hp 2 cylinder 2 stroke oil mix outboard making squeal noise just below lower cowling

I have an old 1998 Yamaha 2 cylinder that has sat more then it ever has ran. Got it running good and it has plenty of power for a 16 foot Carolina Skiff. Coming in tonight it sounded and felt like at first it was running out of gas dragging down and then surging forward. When I came into the creek and came off plane it was making a squeal right at the base of the engine. Sounded like a dry ball bearing in a electric motor. It idled OK and did not appear to be any load on it. Water was coming out of pee hole and motor was not hot. Motor itself sounded fine. By the time I idled up the creek to home (about 10 minutes) it was not making the noise. Heard it last time I was out. Same thing but then I did not get the maybe tight bearing dragging it down filling. Oil is clean in lower unit and it is free. I took a stethoscope to the engine at fast idle in gear tied up at my pier and all sound smooth. By then I could not hear squeal since it only appears to do it after a few mile run. When I check the upper bearing, its fine. Interesting when I put the probe on the lower section of the advance plate just below flywheel, it sounds rough. However, I am sure the noise is lower.. Could it be water pump. I put motor up about 5 years ago and it has sat all this time. I fogged it good and turned it over with the pull start when ever I walked by but basically has sat on a lift all that time. Could the lower crank bearing have rusted? Any ideas. Thanks

[rodbolt17]

that's what it sounds like, rusted ball bearing.
not the first time I ever saw one do it.

[grf00]

Think it's possible that it's the lower unit top bearing just below water pump? When I stethoscope the motor, the bottom bearing sounds smooth like the top one. Figured I would drop lower unit, remove water pump and see what drive shaft feels like when I turn it. I do not really want to tear into motor. If I remove the outer plate and bearing housing bolts just below water pump , will I be able to pull the bearing housing up to replace that top bearing? Appears on the parts fish, if the drive shaft has to be removed to get bearing off, then all the propeller shaft and gears have to be pulled also.

[rodbolt17]

nope.
its not the lower.
only way to access the lower crank bearing is removing the crankshaft.
means splitting the block.

[TownsendsFJR1300]

Should you decide its too expensive to repair properly, a couple of suggestions as you have nothing to loose:

Pull the lower carb(s) reed valve.

Put some engine oil into the lower end of that bad cylinder(#3) so oil drips down to the bearing in question.

Slowly rotate back and forth to get that oil in that rusty bearing. Either trim the engine up or remove and tilt to allow that oil to seep back out. Repeat until no more rusty oil comes out.

The bearing will likley be damaged already however, you should be able to get any rusty particles (that WILL cause more damage) out of the engine, score the cylinder, etc. You may very well get some more hours out of the engine.

And NO, this is NOT the correct way to repair the engine, a new bearing is..

[99yam40]

That sounds like a good way to trash a motor, it will not fix a bad bearing.

and hope it is not in a real bad situation , like a barge heading at you in the canal or in way of something else when it gives up the ghost.
Very different from land based motors.

Trying to paddle a boat out of the way or swim out of the way is not a good thing.
Had to do it once.
I try to make sure the motor I am running is in good shape now a days.
I guess as we age we do not feel invincible anymore

[greasyshaft]

Could be the lower crank seal housing, it has a collar that runs down the drive shaft about 5cm (in NZ anyway)- if this is bogged with salt/corrosion it will bind to the drive shaft.
Ive seen it happen on the 8hp, but it the engine will be very tight to turn over, if not seized.

Drop the lower unit and check the top of the drive shaft for wear.
If it's fine, bearing bearing bearing bearing bearing bearing

[grf00]

Dropped the lower unit. Checked the top of the drive shaft for wear. The spline still had grease on it and there is a shiny narrow band (.025 wide) below spline but this is a static seal on the parts fish for a 1998 25 2 cylinder MSHW. There is some problems with lower unit. Unless I lift up slightly on drive shaft, in gear or out, it appears to have a little bumpy fill. Just spinning the prop shaft with it out of gear is smooth. I pulled the upper bearing retainer and seal housing just below water pump (pump was OK but will replace). Removed the two shaft seals and shift rod bellow seal. No water and clean oil. The small needle bearing appears to be fine. Shaft bearing area is smooth but appears to be a little worn. Not sure if I can measure it down in there but it appears to be maybe about .0015 (English) play in shaft. Not a lot but some. I think that bumpy fill is where the shaft is dropping down letting the gears get too close. When I pull up on shaft and turn, it's smooth and oblivious when under a little load from the prop in the water, that would tend to push the gears apart and push up on the lower tapered roller bearing and that would hold the proper gear spacing like I fill when I pull up on shaft. Someone probably did not get the shimming quite correct since the lower unit appears to be a rebuild. (paint does not quite match). Anyone else felt this condition? 99yam40, I hear you. I am on a small creek (called the Harris River) that leads to the Chesapeake Bay. I stay in the creek but even were it opens up, it can get pretty rough for a 16' Carolina Skiff. And at 66, I am way too old to paddle. That is why I am trying to access the problem. Was just hoping it's not a basket case. That lower bearing is lubricated by the oil mix ? Surely, it's not a sealed bearing. Also, I am not the kind of person who can sell it that way either .. Any more thoughts from this last post? Appreciate the comebacks from all. Thanks rodbolt,Townsends,99YAM40 and greasyshaft (do you by any chance know a guy with the handle 'Spanner' rides a Harley and lives in NZ )

[rodbolt17]

most likely the lower crankshaft bearing NOT a lower unit issue.
if its to much for you I do buy things like this.
along with old military rifles.
carolina machine in Wilmington NC can rebuild the crank assy ,typically its about 300 dollars on a two cyl crank.

[grf00]

Could be the lower crank seal housing, it has a collar that runs down the drive shaft about 5cm (in NZ anyway)- if this is bogged with salt/corrosion it will bind to the drive shaft.
Ive seen it happen on the 8hp, but it the engine will be very tight to turn over, if not seized.

Drop the lower unit and check the top of the drive shaft for wear.
If it's fine, bearing bearing bearing bearing bearing bearing

Did find a seal for the drive shaft were it enters crank but on the motor, its simple a static seal that prevent water from getting into end of crank that drives shaft. 93101-13M37-00 OIL SEAL --- OIL SEAL for drive shaft going into bottom of crank $4.10

[99yam40]

Rodbolt17 is a Yamaha master tech if you have not noticed this before,
So you should pay attention to his posts as he does this stuff for a living and helps people out on this forum with advice

[grf00]

Rodbolt17 is a Yamaha master tech if you have not noticed this before,
So you should pay attention to his posts as he does this stuff for a living and helps people out on this forum with advice

I have and I am and I appreciate his comeback. But I am hoping. Ordered the new seals and stuff to get my wild goose chase on the lower unit back together. Hoping the idle squeak is the water pump I put in in 2006. Not a lot of hours on it but it has sat out in the sun at my pier for 8 years. It's still soft but set and who knows. The squill goes away just a little off idle. I sure hate splitting the block. Lot of parts. Yamaha makes good stuff.

[TownsendsFJR1300]

In regaurds to the one question, re lubrication to the bearing, yes it has to be the pre-mix (or auto lube) that lubes it (not sealed).

If that lower bearing failed badly, its possible it would now allow the crankshaft up and down movement in the block slightly. (The bearing OD would be clamped in the case, the inner ID to the crank). The top bearing, if good, may prevent this..

While the lower unit is off, if you can push that crank up and down, that would confirm something (that bearing) failed.

I've had the main crankshaft roller bearing cage (under the center sprocket) actually partially come apart in one of my old motorcycles (1989 Kawasaki KLR 250). That bearing is lubed with the engine oil (4 stroke). Every 32,000 miles it let loose. At 64,000 it started making racket again and needed replacement. Split enginne frpom frame, split cases, pull transmission, press the bearing off the crank, press on a new one, etc.

[99yam40]

I have and I am and I appreciate his comeback. But I am hoping. Ordered the new seals and stuff to get my wild goose chase on the lower unit back together. Hoping the idle squeak is the water pump I put in in 2006. Not a lot of hours on it but it has sat out in the sun at my pier for 8 years. It's still soft but set and who knows. The squill goes away just a little off idle. I sure hate splitting the block. Lot of parts. Yamaha makes good stuff.

Hope is something, but not the best.

Letting a motor sit will let internal shiny parts rust

that is a long time on water pump replacement and every thing else you did not do.

good luck

[grf00]

Townsend, I'll check that tomorrow. With the lower unit off, I had planned on removing plugs and see what engine felt like. I will also put an indicator on the fly wheel and check end play. My guess is it should be very small. Probably less then .001 . Manual does not spec it. However like I said, with a precision two ear stethoscope, both upper and lower main crank bearings sounded fine at idle. Just a smooth whirr sound of them turning. Both bearings are ball and no seals, so they are lubed by the 100-1 oil premixed gas. I'm old school and usually mix it 75-1 just see a trace of blue smoke. See little carbon build up on piston tops and plugs.

99, I was watching some Youtube and they were saying replace water pump ever two years. At my age, if it pees the Urologist says be happy? HA... You're right about a lot of neglect. Few years ago, Hurricane Isabel came thru and surrounded my house with 3' of water just below living space and I am 9' above average high tide. It tore the boat free and floated it over my neighbors 3 foot chain link fence into his back yard. Took me two days to get it back over and onto my dock. It just may have gotten water in motor but it never went under.