HPDI lower unit nightmare

[MichAngler]

This is a 2005 60X VZ250TLR

I have had issues with my lower units for 2 years now and I’m at my wits end

At the end of the season 2018 I found water in the lower unit
Went to a guy at a local marina and he said he could take care of it that it just needed a new set of gaskets at a decent price so I told him go for it and do the impeller at the same time

Got it done and he told me it was good to go just change the lube at the end of the season like normal

When I went to change the lube at the end of the season the two drain screws were not really tight
Meaning it took little effort to loosen them and again I had water in the lower unit

So he looks everything over and tells me that the shaft is just slightly out of tolerance (wobbles) and needs to be replaced
So he did the shaft and the gaskets and says good to go - now the start of 2019
And the end of the season again the two screws are not very tight again and 1/3 of what came out was clear water

Over this winter he got hurt and couldn’t look at it and by the time he was ok the lock down had been put in place
So I’m thinking the screws are the problem and refilled the unit and norqued the screws down
I’ve been out a total of 5 times this season – 5 times for me equals about 70 miles being I fish St Clair
And after a day in the rain yesterday I went to pull the plug and you could smell a distinct lower unit lube odor so this morning I go to drain the lube and again the drains screws were not very tight I drained the unit and this is what I found (see below)

Note: for the first 12 years I used the same drain screws and they were always tighter and harder to loosen at the end of the year, ever since I replaced the screws it’s just the opposite.

I don’t want to say the guy’s name because he’s a decent fellow and I’m still hoping we can resolve this but I’m ready to just buy a new lower unit and be done with it

I’m tired of missing days on the lake

Attachment 409980

[Amistad Tackle]

You say replaced gaskets. Don't you mean seals? I am not familiar with the HPDI lower unit, but every other one has seals that should be replaced. Did he run a pressure test after the repair?

Also, when you are draining and refilling your lube are you using new washers on the screws each time? These are crush washers and should be replaced each time you do a lube change, otherwise it will leak.

[MichAngler]

Yes Seals sorry

As for the washers I had him replaced both the screws and washers each time including new ones I bought this spring

The funny thing is for the first 12 years I never replaced the washers or screws and never had an issue until 2 years ago when all this started

He did a pressure test before he started and you could see it was losing pressure and you could see lube and bubbles coming out around the shaft
I assume he did the pressure test when he was done both times but this was all done in the shop and I wasn’t there to witness it

I left him a message this morning hoping to get another pressure test quickly so we can see what the heck is going on

[MichAngler]

The thing that I keep thinking about is the drain screws

Prior to this issue I would tighten them by hand (two handed grip on a large screw diver) and at the end of the year it would take a wrench on the screw driver to pop them loose

Now its the other way around

it takes little effort to loosen them (less then I used to tighten them)

[Nutoy]

Has the shift shaft seals been replaced?

I'd lean towards a leaking seal. A pressure test will verify.


I've never replaced the gaskets on the fill/drain screws and have never had a problem with them leaking. Just tighten firmly with a big screwdriver.

[Tx Champ]

...I've never replaced the gaskets on the fill/drain screws and have never had a problem with them leaking. Just tighten firmly with a big screwdriver.

Same here

[MichAngler]

Has the shift shaft seals been replaced?

I'd lean towards a leaking seal. A pressure test will verify.


I've never replaced the gaskets on the fill/drain screws and have never had a problem with them leaking. Just tighten firmly with a big screwdriver.

Yes the shaft seal was replaced twice!

The first time as part of the seal kit
The second time when the shaft was replaced

For 12 years I never changed the gaskets on the drain plugs with no issues

When he first looked at it he told me they should be replaced every time you do a lube change
And since the old screws have some wear in the screw driver slot from years of maintenance I figured I’d replace both and have replace both the screws and gaskets each time since just in case

The old gaskets are a dark red and a little thicker compared to the new ones that are black and slightly thinner

Since the only thing I see differently is the fact that the new screws don’t stay tight and not to mention it’s a holiday weekend and I doubt I’ll hear from him until next week I’m thinking of refilling the unit and using the old screws and gaskets and run it for a few trips and drain again just to see if that is the issue

[201pro]

Sounds like you need a new mechanic. I have used the old red seals for over 16 years with no issues.
I replace them every other time the lower unit fluid is replaced.

[MichAngler]

Sounds like you need a new mechanic. I have used the old red seals for over 16 years with no issues.
I replace them every other time the lower unit fluid is replaced.

That just might be the case

But I’m not willing to call someone out and tarnish someone’s reputation until I have proof

I’m still not convinced that the screws and gaskets aren’t the problem

And you can’t blame someone for suggesting a maintenance procedure that works for them

I refilled the unit and put the old screws and gaskets in and I'm headed out tomorrow I’ll put another 100 miles on her over the next week and we will see

I’m also in the process of trying to find a pressure tester so I can do a test myself

[JDI]

As Nutoy ask, was the SHIFT shaft seal replaced? If it was replaced but put in the wrong way it will pressure test fine but move it a hair and it will leak like hell. It is very easy to put it in the wrong way.

[MichAngler]

As Nutoy ask, was the SHIFT shaft seal replaced? If it was replaced but put in the wrong way it will pressure test fine but move it a hair and it will leak like hell. It is very easy to put it in the wrong way.

Yes as stated the shaft seal had been replaced twice

He contacted me Sunday afternoon and is going to get over here sometime this week to do another pressure test

I got out yesterday and put 32 miles on her and didn’t smell anything or see anything
I plan on getting out tomorrow and put a few more miles on her

I’ll wait for him to drain it and see what the lube looks like and just as important to see if the old screws and gaskets are holding better than the new ones did
But if the screws are holding tight and the lube looks like it did last time there is clearly an internal seal issue no matter what the pressure test shows

[21XDC]

Roy, there is a difference between shift shaft and prop shaft seals.

[MichAngler]

I wasn’t there when he did this

I bought the two kits for the first time (unit and impeller) and I just paid him for the kit when he did the prop shaft the second time

I’m assuming he replaced the correct seals each time

but I will say I'm done paying for this

[Nutoy]

Both, the prop shaft, and the main shaft require two seals each. The "open" side of both seals face outwards.

The shifting shaft requires a O-ring and one seal. "Open" side faces outwards.

Also have him check the "shift" shaft plate. They can get damaged during removal. A lube should be applied to the plate and O-ring on installation so the O-ring doesn't get damaged.

Also check the prop shaft and the main shaft for "wear" in the seal areas. The slightest nick or burr, can and will destroy the seals.

I've seen a lot of guys continue to have water intrusion problems after having the seals replaced, and the mechanic didn't replace the "shift" shaft seal and O-ring.

[john tr 21]

You need to replace upper seal where the lube was bubbling out under pressure , your problem is there

[CJ1]

If you overtighten the new black seals they have a good chance of leaking. I am sticking with the old design until I run out. CJ

[Hawglip]

I used a torque wrench to tighten the drain screws with the new washer to the 7nm that is specified and I will tell you that is tighter than you can get it with a screwdriver. I was surprised.

[cwilt]

Also when you pressurize the lower unit dont go over 10 psi and it is supposed to hold that pressure for a minimum of 10 seconds with no oil in lower unit.
this is my opinion, i hate the new plastic seals Yamaha has made for the oil drain screws. I prefer the old fibrous type. My book also says 5.1 ft lbs for the torque of the drain screws. Good luck.

[SkeetRJ]

They are only going to pressure to a certain PSI then break the seal. The better test is to vacuum test your lower unit. The Yamaha seals let oil out but not water in by design, so pulling a vacuum will let you know if water can come in.