Noisey lower unit?

[1pooldoc]

Just replaced my lower unit with a new Yamaha unit. When I got it installed I tried it out on flush muffs and water pump is working and it shifts well. Without the prop it is as quiet as can be, add prop and shift to forward or reverse and there is a rattling/knocking sort of noise. Goes away in neutral. Called tech at the dealer I bought it from and he suggested that the shift rod was not fully engaging the clutch. Removed the unit and realigned the upper and lower shift rods and adjusted the shift cable. Still have the noise in gear. Kinda at a loss what it could be and a fix. Hard to tell the exact location of the sound. Dealer is not local. Any ideas?

[jimsch]

Added to Yamaha boards. Hope you get it fixed.

[Pulsare2020]

Is it possibly "prop rattle" from a worn hub or incorrectly installed prop washers or torque? Does your prop have a pressed in hub?

[billnorman1]

I had a similar noise with my Suzuki. The mechanic at the dealer said it's not unusual with a stainless prop. Two years, no issues.

[1pooldoc]

Tried it with two different props. Pressed in hub on sho prop and flow torque on fury. Same sound with each. May launch boat and try it with prop loaded to see if it persists.

[ssmithboats]

noise doesnt generally mean anything is wrong i have had torqemasters new that sounded like a box of rocks were in it when the prop was spun.

[mrdeath]

It's prop rattle, and you shouldn't be putting it in gear on muffs with no load on it. If it's new, it should have a warranty. Go out and run it.

[Wackyjig]

It's prop rattle, and you shouldn't be putting it in gear on muffs with no load on it. If it's new, it should have a warranty. Go out and run it.

This. Put it in the water and it'll be gone.

[Johnnyred]

If your setup is compatible, Yamaha makes a SDS hub that makes prop chatter and shift clunk almost disappear. If you can use a Mercury square hub, then the newest Merc/Quicksilver SSR hub if compatible does the same. Both make a world of difference. Ran an SDS hub on a Yami SHO 90 and the newest SSR on a Merc 150 FS.

[Highcentered]

It's prop rattle, and you shouldn't be putting it in gear on muffs with no load on it. If it's new, it should have a warranty. Go out and run it.

My Merc inline 4 did it bad fresh off the trailer when not under a steady load around the ramp. I always assumed it was from the slack in the shims to allow for the metal to expand as it heats up. That's the first thing I thought of when I saw the OP in this thread.

[1pooldoc]

Ran it today and seemed to be okay except for a couple of things that I don't understand. 1. Motor is much louder when running, way louder. 2. Turning 2-300 more rpm but slower top end with no adjustments to p2p or anything else. Same prop as before. 3. When shifting from forward to neutral the motor revs momentarily about 100 rpm then slows back to normal. Not sure why that could happen but one thought is the shift cable may be adjusted to shift to neutral too soon before throttle is fully closed. IDK. Any ideas? Thanks for the help.

[354vZuk140]

Wonder if the mating surfaces are off a little, new lower to current/old mid section. It might make mesh of the gear more audible especially under no load and maybe some exhaust is escaping there also to account for it being louder. You could drop it again and put something on the surfaces, mate them, torque them, drop it again and look at the surfaces. I have used the red sticky grease for similar stuff. Put it thin and even on one surface.

Maybe someone else will have something better! I would look for a part number also on the lower to dbl check that.

[1pooldoc]

Update. Dropped the lower unit again today and looked things over after checking around on Marine Tech site. One thing stuck out was the Damper seal was not installed. I removed the one from the old unit, placed it on the new one, and reset the input shaft collar on the water pump. Off to the water to water test. Engine was as quiet as new. No exhaust noise and no "chatter". Little things can mean a lot if not attended to. Guess this has me ready to go just as the weather gets cold and messy later this week. Going fishing anyway!

[354vZuk140]

[Mike2718]

Update. Dropped the lower unit again today and looked things over after checking around on Marine Tech site. One thing stuck out was the Damper seal was not installed. I removed the one from the old unit, placed it on the new one, and reset the input shaft collar on the water pump. Off to the water to water test. Engine was as quiet as new. No exhaust noise and no "chatter". Little things can mean a lot if not attended to. Guess this has me ready to go just as the weather gets cold and messy later this week. Going fishing anyway!

You are right about “little things can mean a lot.” I have seen the same noise issues on Yamaha engines if you do not “pull up” on the drive shaft at the same time as you are setting the collar. There is just the slightest hint of upward play on the driveshafts of Yamahas that I have seen. I have never owned a Yamaha but a couple of friends have them. We ran into the same “noise” issue too after replacing the water pumps. A mechanic told me about pulling up on the driveshaft as you’re setting the collar. My friends never had those noises anymore once we started doing that.

Glad to hear you got your issues fixed.

[1pooldoc]

One question I have come up with through this is: When should I replace the collar on the driveshaft? Mine's a little "less tight" than when I took it off. Difficult task to do this alone. Need three hands if you don't have the special tool to reseat the collar.

[Mike2718]

One question I have come up with through this is: When should I replace the collar on the driveshaft? Mine's a little "less tight" than when I took it off. Difficult task to do this alone. Need three hands if you don't have the special tool to reseat the collar.

I don't know enough about Yamaha motors to answer when they need to be replaced. What I did for my friends units was to take a piece of "chopping board" material and drilled a hole so it would barely slide over the drive shaft. Use a piece wide enough so it has enough room to hammer all around the edge of the "chopping board". I would hammer around the edges until the collar is set to the proper depth.

I have also used a piece of metal pipe and slid it over the driveshaft then "slammed" it into the "chopping board" until it is set to the proper depth. When using this method, I usually wrap a little bit of cardboard around the driveshaft to keep from scratching it. You don't have to "slam" it into the chopping board super hard. You just need to "slam" it enough times to set the collar to the proper depth. I prefer this method because it applies even pressure around the collar. I just let the weight of the pipe do most of the work.
You don't need a very long piece of pipe and don't forget to pull up on the driveshaft as you are setting the collar.

You could probably use a piece of wood instead of a chopping board. The key is to make sure the hole is JUST big enough to get it over the driveshaft.



If you are working solo, you can make a nice lower unit stand out of a couple of saw horses, couple of 2x4's about 3' to 4' long and a couple clamps. Lay the 2x4's across the saw horses just far enough apart so the cavitation plate can sit FULLY on the 2x4's. Lower the lower unit onto the 2x4's until it is sitting on the 2x4's. Take one of the clamps and lay it across the 2x4's on one end and do the same with the other clamp on the other end. Now tighten both clamps at the same time so that the 2x4's cannot spread apart. This will also snug the 2x4's against the lower unit.

You can also use tie down straps around the the 2x4's to keep them from spreading apart. As long as the 2x4's can't spread apart, the lower unit isn't going anywhere. The weight of the lower unit will keep it from moving around and that makes it easy to work on it if you don't have a helper. You will also be able to set the collar by yourself.

Good Luck

[1pooldoc]

Thanks Mike I used a black and decker workmate. It clamps the unit between 2 boards and makes a perfect stand I used a 7/8 boxend wrench to seat the collar. Cumbersome so next time i think I'll try your way.