Is This Normal? (Yamaha 40hp 2 stroke)

[Ruggybuggy]

I just purchase a 2004 Yamaha 40TLRC that is like new. It has about 15 hours of use on it. Today after mounting it to my boat I started it up in the yard with the ear muffs on to run some Seafoam through it and notice at idle and in gear a rattle noise which seams to come from between the lower unit and powerhead. It rattles in both reverse and forward but stops as soon as the motor is placed in neutral. When in gear and off idle the rattle seems to quiet down. Is this normal? I was thinking that because there is no load on the prop this was some how responsible. I don't want to pull the lower unit off if I don't have to. From what I know the 3 cylinder Yamaha 2 strokes are bullet proof and this motor has very little hours on it.

Thanks in advance!

 

[99yam40]

Re: Is This Normal? (Yamaha 40hp 2 stroke)

Have you checked and changed the lower unit lube to make sure there is not a problem with it?
Have you changed the water pump and thermostat?

 

[Ruggybuggy]

Re: Is This Normal? (Yamaha 40hp 2 stroke)

I did change out the lower unit lube. It looked clean and the magnet had next to nothing on it. Thermostat and water pump are the original and never thought about changing them because I don't have an over heating problem and the motor has such low hours. I listened to a friends Yamaha 50hp 2 stroke and it didn't make any rattle noise while running on the muffs.

 

[Ruggybuggy]

Re: Is This Normal? (Yamaha 40hp 2 stroke)

Well I just got in from removing the lower unit and did't see any issues. The water pump impeller looked fine. I could no duplicate the rattle by turning the input shaft by hand. I was maybe thinking the shift rod might be causing the problem?

I put everything back together and it still makes the rattle noise. It's not the shift rod.

 

[Ruggybuggy]

Re: Is This Normal? (Yamaha 40hp 2 stroke)

Bump!

 

[Ruggybuggy]

Re: Is This Normal? (Yamaha 40hp 2 stroke)

Someone must know!

 

[99yam40]

Re: Is This Normal? (Yamaha 40hp 2 stroke)

If it was not stored properly for all those years(Fogged to coat internals will oil) you could have rust on internal parts.

I would still pull, clean, and test thermostat and look at cooling passages just to see what condition they are in and make sure stat is functioning as specs call for.
The rubber impeller gets old and stiff and needs to be replaced every few years even if it does not show signs of being wore out.
I have heard of fuel pumps making a ticking sound if they were sucking air from some where and are not completely full of fuel, but not sure if that motor would do that.

 

[Ruggybuggy]

Re: Is This Normal? (Yamaha 40hp 2 stroke)

Thanks for the reply. I will give it a try and let you know how it goes.

 

[robert graham]

Re: Is This Normal? (Yamaha 40hp 2 stroke)

Maybe those spring washers on top of water pump causing rattle in drive line, or drive shaft bushing needs replacing or lubricating? My 90HP used to have a rattle in the black plastic slide on the throttle/shift cable mechanism, but I tightened it up with some tie-wraps. Let us know what you find!

 

[Ruggybuggy]

Re: Is This Normal? (Yamaha 40hp 2 stroke)

Maybe those spring washers on top of water pump causing rattle in drive line, or drive shaft bushing needs replacing or lubricating? My 90HP used to have a rattle in the black plastic slide on the throttle/shift cable mechanism, but I tightened it up with some tie-wraps. Let us know what you find!

I did take the lower unit off and greased the shaft before reinstalling. While it was out I checked the water pump impeller and all was good and bolts were tight. Put it back together and still had the rattle. I thought maybe the shifting rod was vibrating but when running if I hold the rod the noise is still there. It sounds like the noise is coming from between the power unit and lower end. It's an irregular rattle and sounds as if something is coming loose but there really isn't anything between the power head and lower end. Almost sound as if someone was tapping on the motor with a wrench in an irregular fashion. I'll try to post a video of it.

Thanks for your help so far!
Dave