Texas Fishing Forum

300 Yamaha lower Unit

Posted By: Chuck72

300 Yamaha lower Unit - 06/09/18 04:58 PM

So I bought a boat that had 324 hours on 2005 300 hpdi. The lower unit had damage to the skeg and only to the skeg.. I changed the gear oil right after I purchased and it was a little dark but had very little metal and the lower unit seemed mechanically fine.

I was not comfortable with the broken skeg and you fine folks on here advised me to change the case out. At this point I had 326 hours on the motor. I had an individual on here replace the case and now at 337 hours I have no reverse, metal shavings everywhere, but forward seems to work.. there is no noise or grinding but there was evidence of a little water in the oil. I have blackish green oil with a metallic glow.

Is this common after a case change? I get it that new gears often throw a lot of wear on the gears as they seat into each other, but these are not new gears..I have never taken a lower unit apart, but want to see what the issue is. After 11 hours of running mostly at low RPMs graphing I am concerned about the workmanship I got..

I have the lower unit off the boat, so I am certain it is in the Lower Unit that is issue. When I try to shift manually it is all stop, there is no give on the shift shaft it doesn't feel like anything is moving internally.

I can't really afford a new lower unit, but if I have to I will.

Looking for advice.
Posted By: ssmith

Re: 300 Yamaha lower Unit - 06/09/18 05:50 PM

why not take it back to the folks that took your money?
Posted By: Chuck72

Re: 300 Yamaha lower Unit - 06/09/18 08:28 PM

Originally Posted By: ssmith
why not take it back to the folks that took your money?


Might be an option, it will require me to ship the unit. I am sure this is a 30-45 day route.. it may however be quicker than any marine mechanic around San Angelo. Haven't spoken to to him yet. Just trying to see if his is out of character for a lower unit.
Posted By: T-racer @ Mallard Marine

Re: 300 Yamaha lower Unit - 06/10/18 03:12 AM

It sure is. Call them. Sometimes freak things happen but that’s not normal.
Posted By: steve@S2Marine

Re: 300 Yamaha lower Unit - 06/11/18 12:54 PM

if you still have your original lower unit... why not just have a prop shop
re weld the skeg?? that would have been a lot cheaper.
Posted By: spankyttx

Re: 300 Yamaha lower Unit - 06/11/18 01:25 PM

i've always wondered why you guys say NOT to weld skegs over so many horsepower? honestly steve, i thought you were on board saying that too, but it could have been others? i'm for welding myself, i've straightened welded skegs that were "not repairable because it had been welded". these were rolled over into a j too and never broke or split a seam
Posted By: steve@S2Marine

Re: 300 Yamaha lower Unit - 06/11/18 04:26 PM

Originally Posted By: spankyttx
i've always wondered why you guys say NOT to weld skegs over so many horsepower? honestly steve, i thought you were on board saying that too, but it could have been others? i'm for welding myself, i've straightened welded skegs that were "not repairable because it had been welded". these were rolled over into a j too and never broke or split a seam


I'm always for welding skegs, unless it's a merc skeg and they are surfacing the case. and over 85mph.

typical bass boats are no problem welding skegs.. especially yamaha skegs.. that's easy metal to weld up.
Posted By: Chuck72

Re: 300 Yamaha lower Unit - 06/12/18 01:16 AM

Originally Posted By: steve@hydrodynamics
Originally Posted By: spankyttx
i've always wondered why you guys say NOT to weld skegs over so many horsepower? honestly steve, i thought you were on board saying that too, but it could have been others? i'm for welding myself, i've straightened welded skegs that were "not repairable because it had been welded". these were rolled over into a j too and never broke or split a seam


I'm always for welding skegs, unless it's a merc skeg and they are surfacing the case. and over 85mph.

typical bass boats are no problem welding skegs.. especially yamaha skegs.. that's easy metal to weld up.


Hindsight.. There were several people on here that convinced me not weld the skeg, didn't want to be an Alton if it came unbuttoned. Their arguments made sense.. I can rationalize it either way, as I have spent a lot of time welding and inspecting welds. At the end of the day my 9 year old daughter often rides in my boat, her safety is worth replacing it, so that's the route I took.. and it's just that simple.

I am in the process of tearing this down myself, learning as I go.

My brand new water pump (10 hours of use) looks like its a season or two old, but definetly not the water pump I sent in on my old unit. To many things point to this not being a new water pump based on the wear. I am familiar with these as I change my own every year.

The main shaft will rotate between 1/2 & 3/4 rotation before the prop shaft turns.
The prop shaft slides about 1/8 inch in and out of the carrier.
It is very noisy without gear oil in it, sounds like the bearings to me.
It clearly will not go into reverse still.

Don't have the tools to pull the shaft so currently weighing my options.
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