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Merc 25H making squealing noises, help!


EBass

Question

I have a 1988 25H merc manual start. Last night I noticed when I slowed down this higher pitched squealing sound was coming from my lower unit. At idle it went away. Then went to a different part of the lake and now it's louder and it still squeals at idle and gets louder when I give her gas. I shut her down a used the trolling motor.

My friend thinks it's my water pump. Has anoyone ever heard of this? Could my lower unit be shot? Would that make a different sound?

I'm a first time boat owner and I have no idea.

Please help out if you can.

Thanks,
EBass

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I called a good mechanic and explained the issue to him. He thinks it's the bering below the water pump. He said to drain and lube the lower unit and if that doesn't help then a rebuild of the berings needs to take place and it's not a fun job he said. In other words $$$. Has this happened to anyone?

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  • 'we have more fun' FishingMN Creators

The bearing is easy to replace. It sits under the water pump. While your replacing the bearing put in a new inpeller.

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Really, he said that it needs to be adjusted to the proper level.

Have you replaced yours before??

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Thanks Surface Tension.

The guy from Supreme Marine said to take off the lower unit and start it. If it makes the squealing sound then it maybe it's the power head. But from where the sound is coming it diffenently sounds like it's coming from the middle of the lower unit, which I assume is the impellar and the bearings.

OK so let's say I replace the bearings and impellar. What's the trick to get the lower unit back on? My handle is the shifter and throttle. Doesn't it need to be in gear or something. Putting them back on is the tricky part

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  • 'we have more fun' FishingMN Creators

Sure you can pull the lower unit and start the motor to see if the problem is there. Put the motor in forward before you pull the lower unit off. Dont pry if it dosent drop, make sure you get all the nuts and bolts off. Merc's have a problem where the driveshaft freezes to the powerhead. In fact I have a 35 merc that on working on now thats froze. If this is your case stop there and post.

Ofcoarse run it for just a short time. When you put the the lower unit back on turn the prop till the driveshaft splines lineup with the powerhead.

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Thanks for all your help Surface Tension. I appreciate it.

I'll work on it tonight or tomorrow. If it doesn't drop I won't push it. I'll screw it back on and post.

I did make an appt at Elko Motor Small Engine repair. To drop it off next week. Ever heard of them?

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  • 'we have more fun' FishingMN Creators

Ebass Yes I have replaced them.
To check the bearing all you would have to do is pull the water pump. Easy to do.

If its bad then to get bearing out you have to pull the prop shaft also. Theres a nut on the end of driveshaft that holds pinion gear.

Guess I would drain the lower unit and see if you got water in there or worse yet no oil.

You can get a manual and replace the bearing yourself or bring just the lower unit along with the pump to get it replaced.

[This message has been edited by Surface Tension (edited 07-18-2003).]

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Hey Surface Tension,

I changed my lower unit lube and brought it in. Well he put it in the tub and didn't hear anything. He adjusted the carb but that's it. So I get it back and I'm all happy right,... wrong.
It's running like a champ then do some fishing. Try to start it and it's taking it's sweet time. Get it going then give her some gas and she kills. Did it a few times but did get it going.

Next day started up and ran great, did some fishing then went to start it and again she kills when I give her gas. What the..? I get it going then that dang squealing noise comes back and will only shut up when put in gear and no throttle.

So it seems when she's run hard she starts to act up. Why would bearings not squeak then squeak again and not stop? Are Mercury's made by Ford secertly?

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  • 'we have more fun' FishingMN Creators

Without seeing it run I'm guessing.
Will it start if you choke it?
Did it go faster after he adjusted the carb?
Was there water and or a glitter look in the gear case oil?
Is it a metallic screech or a rubber like squeak? Does it squeak with a rhythm or is it a constant pitch?
Does it go away a different speeds?

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Thanks for the quick reply. I read that you know STFcatfish. Steve's a good fella.

I can get it to start, sometimes she acts up but it just started killing when I gave her the gas. (This is after the carb was adjusted)

It idled smoother, but I don't think it went faster.

I did see some metal shavings on the maganet, but not a lot. I guess it did look kinda creamy, but more of a brown cream.

About the squeak, it's high pitched and get's louder when at a higher rpm. When at idle she slowly fades away. I give it the gas a tiny bit and the squeak comes back.

I don't know if it's metal or rubber squealing. It doesn't sound like metal grinding, just a high pitch, eek, eek, eek..etc get's louder and faster when rpms go up.

All these "symptoms" start to happen after she's been ran for a bit. Which sucks cause I'm all across the lake then it gives me crap.

Sounds like my truck problems, just weird to diagnose.

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  • 'we have more fun' FishingMN Creators

The mechanic leaned out the carb to much.

The squeal I cant pin down without hearing and seeing the motor. Theres just to many things it could be.
If your headed up to see Steve and Lisa drop the motor by on your way.

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That's what he (mech) said about the carb/killing thing.

The squeaking thing is a pain in the you know what. I didn't notice a drop in performance, YET. Tonka Boy another FM member and highschool grad might take a look see. Plus he lives in the cities.

Thanks for the offer to look at it. I don't think I will be heading to Ely anytime soon.

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surface tension,

Here's what I found out so far. Took off the prop. Major line wrapped up against the seal, but the seal looks fine. Cleaned it all off. Drained the lower unit and it looked brand new. Tried to get the lower unit off. We got it to drop an inch but that was it.

This merc has the shifter on the throttle. There's no way to rev the engine while its in neutral. So I'm wondering if the shifter has something to do with it not dropping.

I think I need to go get the manual. We're missing something. Any thoughts on why it's not dropping? I don't think it fused to the power head as it did drop some, but something is blocking it. We did put it in forward, neutral and reverse. Just couldn't get it to drop more than one inch.

Tonka Boy thinks the line was the issue, but I still wanted to get into the impeller and the bearings to take a look see.

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I don't know Mercury too much, but it sounds like your lower unit isn't dropping because the shifter rod is still connected. You need to disconnect it.

On my small Honda OB the shifter rod is exposed on the (front, just above where the lower unit bolts to the casing) outside of the motor with nuts and bolts. I believe that's how you disconnect it....from what my mechanic told me. I don't touch lower units as they need to be properly shimmed and whatnot that goes with re-installation.

I would definitely change that water impeller.

Just trying to help....

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I'm just relaying what my mechanic told me. The minute I heard him say shim this, shim that and it will be ready to go I said "when can I deliver it to you". smile.gif Must be because it's a Honda?

Hope you figure it out.

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Thanks Valv, You've got mail.

CD, I'm all thumbs to, but I'm trying to learn this and save me some $$$. I was quoted $375 to take off the lower unit and replace the seals and bearings. I just spent all my money buying the dang thing. Sheesh, so I gotta figure this out and get her running great again. I like the engine, it scoots along pretty well.

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Whoa! For that price I would take it apart myself too! I use a self-employed mechanic and he only charged me $65 and new water impeller, seals and labor. (I didn't need bearings though, if that's your squeeling noise.)

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Heck ya. That's why this site is the best around. Where else can you talk to fishing peers, actual guides, and mechanics? No where but here. Besides, a zillion minds are better than one.

I'll get her going again real soon here with the tips from everyone. The manuals are great but are spendy and that money could be used for parts or a new reel!!

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  • 'we have more fun' FishingMN Creators

If it dropped an inch it isn't froze.
Some models did require the shift linkage to be disconnected but I think your year is splined like valv said. With it dropped you should be able to see if its hanging on the linkage. What ever you do don't to try pry it off. Use wood shims.

[This message has been edited by Surface Tension (edited 08-08-2003).]

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Im not real sure about mercs either but I believe CD is right,your shift rod is holding you up

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If you had a lot of line in there and the motor didnt run hot and pumped a good stream of water I would put it back together and test it but if you do take it apart you might as well put in a new impeller even if the old one looks good

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Thanks for the replies. We saw that shifter pin like you were talking about. We took off the clip that we thought held it in place, but still couldn't get the shifter pin seperated. I'll look for a bolt underneath.

Tonka Boy said the same, put the lower unit lube back in and give her a run to see, but I am curious to what the impeller looks like. Still works though. Maybe I should just leave it.


CD, shimming the lower unit back on? I thought that you take it off in gear and put it back on in gear then turn the prop till it lines up? We did mess up putting it back on though smile.gif I'll be back at it tonight. Stinking Mercs!!

[This message has been edited by EBass (edited 08-07-2003).]

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Ebass, there is a hidden bolt under the trim tab on back of lower unit, you have to remove tab, then look underneath, you'll see the bolt.
Mercury don't have a shift rod coupler, when you lower unit, rod slides out of a splined retainer. You don't have to shim unit when you re-install it, just align shift rod correctly and driveshaft on flywheel splines (you might have to rotate it a little to re-align), sometimes leaving motor in gear it will help assembly/disassembly, but if you leave it in gear don't touch it until is reassembled.
I would suggest getting a manual, but if you want send me an email and I will reply with 2 parts breakdown drawings.
[email protected], and if you send serial # I can be more precise.

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I still can't find that hidden bolt under the trim tab. Valv or Surface T, can you describe in great detail on where to get to it?

I have that shallow drive platic plate that props up to trim it up. Is that what you're talking about??

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  • 'we have more fun' FishingMN Creators

Theres a plastic plug on the top side of the zinc fin on you lower unit. Remove the plug and you'll see a stub with a nut.

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Zinc fin? I took off the counter balance thing right above the prop, but you're not talking about that. Valv emailed me some diagrams. I have serial # OB351219. So this isn't found if the prop is off? There's two screws not bolts behind the prop. I would imagine bearings and seals and such.

Zinc fin, zinc fin.. if I was behind the boat looking at the prop it would be...?

Sorry man, I feel like an @ss asking all these Q's.

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Eric, no problems, we are here to help, we are all "professional mechanics" wink.gif and we all know what we are doing, right... rolleyes.gif

Anyway look at second picture I sent you, it's part # 39 right below cavitation plate.
It has a bolt to hold it from top, when removed it will reveal a bolt underneath (you have to look upward from prop).
As ST said, DO NOT pry it, it's all alluminum and it gets damaged easily, try to shake it, or sometimes, having a friend doing it, tap ignition key to crank motor a fraction, while you hold lower unit from falling.
Don't mess with shift rod or parts above lower unit.

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  • 'we have more fun' FishingMN Creators

hehe

Yes the fin thats right above the prop.
It balances out props torc. Its zinc to protect your motor from corrosion. Only reason to take the prop off is if it should start your not going to loose any fingers.
The lower unit will separate by the anti- cavitation plate.(big horizontal fin)
No need to pull the prop shaft.(the thing the prop go's on)

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