Alpha One Gen 2 Top Cap Leaking! Help!

crzy2bealive · May 10, 2025

I had to replace some internal seals in my alpha one drive and for some reasons it keeps leaking from the top of the gear case lid.

I originally used permatex form a gasket and that did nothing.

The water made its way past the top plate o-ring to the gears and milked the oil

I switched to permatex black rtv and it slowed down the water leaking.

Doesn’t seem to have leaked passed the top plate o-ring and milk up the water.

Am I doing something wrong here?

The 4 bolts on the bottom top, torque spec is only like 20 something ft lbs.

crzy2bealive · May 10, 2025

I only ran this on the hose so might be too much pressure. Taking it to the ramp tomorrow.

lbhsbz · May 10, 2025

I would use RTV....forget that brown shit.

Apply a thin layer to both surfaces and distribute it with your finger to get it stick to the aluminum, then assemble, this process seems to work best on imperfect / old worn surfaces.

monkeyswrench · May 10, 2025

I've had good luck with Right-Stuff, and applying it like above, thin layer both parts.

HALLETT BOY · May 10, 2025

Are the bolts maybe too long and bottoming out in the holes ?

77charger · May 10, 2025

I like to use 1211 that shit seems to work well for alot of stuff pricey yeh but it works.Need to order since i have a couple jet ski cases to split too.

JUSTWANNARACE · May 10, 2025

77charger said:
I like to use 1211 that shit seems to work well for alot of stuff pricey yeh but it works.Need to order since i have a couple jet ski cases to split too.

In all the years I rebuilt 2 stroke motors it was 1211 or 1184 both great stuff

crzy2bealive · May 10, 2025

monkeyswrench said:
I've had good luck with Right-Stuff, and applying it like above, thin layer both parts.

I’m going to reseal it tonight take it to the ramp tomorrow morning and see what happens. The right stuff says cured in 90 mins.

lbhsbz · May 10, 2025

If you really want it to not leak and you're sure it's together right....use 3M 5200 lol....second only to welding the damn thing on.

crzy2bealive · May 10, 2025

lbhsbz said:
If you want really want it to not leak and you're sure it's together right....use 3M 5200 lol....second only to welding the damn thing on.

Futures owner problem if I use that shit lol

wzuber · May 10, 2025

Often times it helps to let the siliconed parts sit awhile and tack up some, then assembly prats evenly to make full contact but not complete clamping to cause oozing out of joint, let sit overnight and cure, then torque the following morning/day etc. Depending on ambient temps. Assembling too soon can squeeze out from.joint. ymmv

Fun Times · May 10, 2025

crzy2bealive said:
I’m going to reseal it tonight take it to the ramp tomorrow morning and see what happens. The right stuff says cured in 90 mins.

Looks like you might be? missing the Rubber Stuffer Plug in which would fill in the big hole area where you'd then be applying the quicksilver perfect seal which the equivalent is now the Permatex Form-A-Gasket Sealant Liquid you were correctly using by the book around the rubber plug... That plug is also sort of used as a seal for that area should the top cover and drive shaft housing be in good shape, no pitting, flat surfacing, etc..

The stuffer plug would be item number 5A, https://www.mercruiserparts.com/bam/subassemblydetail/46032797/28179843

861738 Plug for sale | eBay

Get the best deals for 861738 Plug at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

Hopefully in this case for best possible fitment you're using the Merc OEM top cover O-ring vs the aftermarket options? , https://www.marineengine.com/newparts/part_search.php?part_num=32546

https://www.mercruiserparts.com/802881a1-perfect-seal

Lumpy · May 10, 2025

Possibly a cracked case? Did you torque to spec? Maybe cap is cracked? Alpha and bravo cases aren’t high pressure…only water intrusion I’ve encountered was bravo lower seals and alpha small o-ring oil seal between the two halves. A properly sealed cap shouldn’t do that. Try a light pressure test…no more than 30lbs. That may reveal the problem.

crzy2bealive · May 10, 2025

Fun Times said:
Looks like you might be? missing the Rubber Stuffer Plug in which would fill in the big hole area where you'd then be applying the quicksilver perfect seal which the equivalent is now the Permatex Form-A-Gasket Sealant Liquid you were correctly using by the book around the rubber plug... That plug is also sort of used as a seal for that area should the top cover and drive shaft housing be in good shape, no pitting, flat surfacing, etc..

The stuffer plug would be item number 5A, https://www.mercruiserparts.com/bam/subassemblydetail/46032797/28179843

861738 Plug for sale | eBay

Get the best deals for 861738 Plug at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

Hopefully in this case for best possible fitment you're using the Merc OEM top cover O-ring vs the aftermarket options? , https://www.marineengine.com/newparts/part_search.php?part_num=32546

https://www.mercruiserparts.com/802881a1-perfect-seal
View attachment 1504989

I actually never had a stuffer plug. When I disassembled it, it didn’t even have any kind of sealant just bad corrosion which I cleaned up with scotchbrite.

And for the o-ring I bought a brand new OEM as I wanted to avoid any issues.

Fun Times · May 10, 2025

crzy2bealive said:
I actually never had a stuffer plug. When I disassembled it, it didn’t even have any kind of sealant just bad corrosion which I cleaned up with scotchbrite.

And for the o-ring I bought a brand new OEM as I wanted to avoid any issues.

You may want to invest in the plug and if possible on your end, perform a pressure test of 7-10 psi and observe gauge for up to 15 minutes.
There are lots of videos on you tube plus this guide from Don S comes to mind as well, https://forums.iboats.com/threads/mercruiser-procedure-for-pressure-testing.437896/#post-3077562

mercruiser alpha gen 2 pressure testing procedure pdf - Bing

Intelligent search from Bing makes it easier to quickly find what you’re looking for and rewards you.

www.bing.com

lbhsbz · May 10, 2025

crzy2bealive said:
I actually never had a stuffer plug. When I disassembled it, it didn’t even have any kind of sealant just bad corrosion which I cleaned up with scotchbrite.

And for the o-ring I bought a brand new OEM as I wanted to avoid any issues.

Got any friends who smoke? Dump the oil, bolt the cover on with some sort of temporary goo to sort of seal it it, shove a piece of vacuum line or similar in the filler hole and have a smoker buddy take a big hit and exhale into the hose....watch for where the smoke comes out. That's how you find a crack you didn't know was there without buying a smoke machine.

Back before smoke machines were a thing....Me or one of the 4 other smokers in the shop used to get called over to do this to find vacuum leaks....used to bill out .5 for it lol.

Fun Times · May 10, 2025

lbhsbz said:
Got any friends who smoke? Dump the oil, bolt the cover on with some sort of temporary goo to sort of seal it it, shove a piece of vacuum line or similar in the filler hole and have a smoker buddy take a big hit and exhale into the hose....watch for where the smoke comes out. That's how you find a crack you didn't know was there without buying a smoke machine.

Back before smoke machines were a thing....Me or one of the 4 other smokers in the shop used to get called over to do this to find vacuum leaks....used to bill out .5 for it lol.

Maybe a Vape pen vs cigarette nowadays

as it seems like every time I see someone take a hit of a pen at a stop light with the window halfway down, I start checking the car over for a fire, overheating or just something wrong somewhere.

lbhsbz · May 10, 2025

Fun Times said:
Maybe a Vape pen vs cigarette nowadays as it seems like every time I see someone take a hit of a pen at a stop light with the window halfway down, I start checking the car over for a fire, overheating or just something wrong somewhere.

That's funny....picked my kid up at school today and on the way home saw a cloud coming off of car in front of us....kid goes "headgasket"? No son, just a vaper lol.

Mikes56 · May 10, 2025

If all else fails, Hondabond.

HST4ME · May 10, 2025

Your missing the plug and all the oring needs is grease. Make sure your drive shower bolts aren't bottoming out.

Outdrive1 · May 10, 2025

You sure it’s not leaking under your impeller and pressurizing the drive until it pushes out past the top cap? Have you changed the seal below the wear plate that the impeller sits on? That’s where I would start.

crzy2bealive · May 10, 2025

Outdrive1 said:
You sure it’s not leaking under your impeller and pressurizing the drive until it pushes out past the top cap? Have you changed the seal below the wear plate that the impeller sits on? That’s where I would start.

Yup I actually replaced the impeller, the seal under the impeller, and the shift shaft seal.

Pressure tested lower unit before reassembly

crzy2bealive · May 10, 2025

Ok no leaks after reseal and just taking it to the ramp.

Not sure if too much hose pressure at the house caused it.

But no more leaks

crzy2bealive · May 10, 2025

Will drain oil when I get back and check for any milky oil

Rennsport · May 10, 2025

Mikes56 said:
If all else fails, Hondabond.

Or Yamabond

mesquito_creek · May 10, 2025

Make sure you torque those four bolts because it sets the preload on the bearings.

The plug should look like this

crzy2bealive · May 10, 2025

mesquito_creek said:
Make sure you torque those four bolts because it sets the preload on the bearings.

The plug should look like this

View attachment 1505163

Yah that’s weird my boat didn’t have a plug,

Now that it’s working I’m scared to touch it lol

crzy2bealive · May 11, 2025

Ok I ran the boat for 5 hours today,

Can someone verify if this oil looks ok? (Aka Has water in it?)

It looks kinda cloudy but not sure if that’s due to old milky oil that needed to be flushed out and being used today?

Yah I’m a bit paranoid because I have a powell trip in a few weeks.

I’m also going to redo a pressure test. 9 psi and I’m going to run to dinner for an hour or 2 to see if it leaked out.

Fresh oil color.

Mikes56 · May 11, 2025

That doesn’t look like fresh gear oil, but it doesn’t look like much water mixed with gear oil either. Maybe leftover moisture in the drive?
Pour fresh gear oil in a drinking glass and pour some of that drain oil into another drinking glass and put them side by side.

Do another drain and refill and run it again if you are worried about it. I would, because it’s easy and cheap to do.

lbhsbz · May 11, 2025

If water is coming in (as opposed to oil getting out)....do a vacuum test instead of a pressure test.

crzy2bealive · May 11, 2025

Mikes56 said:
That doesn’t look like fresh gear oil, but it doesn’t look like much water mixed with gear oil either. Maybe leftover moisture in the drive?
Pour fresh gear oil in a drinking glass and pour some of that drain oil into another drinking glass and put them side by side.

Do another drain and refill and run it again if you are worried about it. I would, because it’s easy and cheap to do.

Definitely cheaper to drain and fill and have peace of mind.

Lumpy · May 11, 2025

Outdrive1 said:
You sure it’s not leaking under your impeller and pressurizing the drive until it pushes out past the top cap? Have you changed the seal below the wear plate that the impeller sits on? That’s where I would start.

My money is on this...

crzy2bealive said:
Ok I ran the boat for 5 hours today,

Can someone verify if this oil looks ok? (Aka Has water in it?)

It looks kinda cloudy but not sure if that’s due to old milky oil that needed to be flushed out and being used today?

Yah I’m a bit paranoid because I have a powell trip in a few weeks.

I’m also going to redo a pressure test. 9 psi and I’m going to run to dinner for an hour or 2 to see if it leaked out.

View attachment 1505228
View attachment 1505225
Fresh oil color.

View attachment 1505226

Yup, water in oil…you mentioned new oil cooler!?!? Why? What seals did you replace? Need a factual breakdown of what you did exactly.

JUSTWANNARACE · May 11, 2025

I know some seals are directional when seperating water and oil. Not sure if the ones that were replaced are or not.

crzy2bealive · May 11, 2025

Lumpy said:
My money is on this...

Yup, water in oil…you mentioned new oil cooler!?!? Why? What seals did you replace? Need a factual breakdown of what you did exactly.

It all started last season with oil leaking out of the lower drive. Coming out of the intake area of the lower unit.

So during the off season I did the following.

Lower unit:

Replaced Impeller
Replaced the cone shaped seal under the impeller. Not sure what it’s called.
Replaced the shift shaft seal.

Pressure tested the lower unit separately with a block of plate.

Held pressure for 24 hours.

On the upper unit.

I replaced the the seal under need the bearing assembly. Not sure what it’s called.

Replaced the o-ring on the top cap.

Replaced u-joints.

No water in the bellows,

Reassembled everything. New seal and o-ring to reassemble onto bell housing.

No more leaking oil.

Ran it on a hose kept leaking water out of the top cap.

Originally used form a gasket

Drive oil came out like mustard,

Silicone the top cap even better with black rtv doesn’t leak water out anymore.

Ran boat for 5 hours today.

Drained oil. Looks better than it did the last time just running it on a hose.maybe residual moisture from when it first had water intrusion running it on a hose.

Currently at a beach drinking

Has 9 psi pressure test will check if it leaked out when I get back.

I have read conflicting information that I shouldn’t vacuum test on a mercruiser. Can someone confirm? Vacuum test was only designed for Volvo drives?

mesquito_creek · May 11, 2025

crzy2bealive said:
Ok I ran the boat for 5 hours today,

Can someone verify if this oil looks ok? (Aka Has water in it?)

It looks kinda cloudy but not sure if that’s due to old milky oil that needed to be flushed out and being used today?

Yah I’m a bit paranoid because I have a powell trip in a few weeks.

I’m also going to redo a pressure test. 9 psi and I’m going to run to dinner for an hour or 2 to see if it leaked out.

View attachment 1505228
View attachment 1505225
Fresh oil color.

View attachment 1505226

That yellow stuff is for the outboards I believe… I use the blue stuff.

4Waters · May 11, 2025

crzy2bealive said:
It all started last season with oil leaking out of the lower drive. Coming out of the intake area of the lower unit.

So during the off season I did the following.

Lower unit:

Replaced Impeller
Replaced the cone shaped seal under the impeller. Not sure what it’s called.
Replaced the shift shaft seal.

Pressure tested the lower unit separately with a block of plate.

Held pressure for 24 hours.

On the upper unit.

I replaced the the seal under need the bearing assembly. Not sure what it’s called.

Replaced the o-ring on the top cap.

Replaced u-joints.

No water in the bellows,

Reassembled everything. New seal and o-ring to reassemble onto bell housing.

No more leaking oil.

Ran it on a hose kept leaking water out of the top cap.

Originally used form a gasket

Drive oil came out like mustard,

Silicone the top cap even better with black rtv doesn’t leak water out anymore.

Ran boat for 5 hours today.

Drained oil. Looks better than it did the last time just running it on a hose.maybe residual moisture from when it first had water intrusion running it on a hose.

Currently at a beach drinking

Has 9 psi pressure test will check if it leaked out when I get back.

I have read conflicting information that I shouldn’t vacuum test on a mercruiser. Can someone confirm? Vacuum test was only designed for Volvo drives?

I vacuum and pressure tested my bravo

crzy2bealive · May 11, 2025

Outdrive1 said:
You sure it’s not leaking under your impeller and pressurizing the drive until it pushes out past the top cap? Have you changed the seal below the wear plate that the impeller sits on? That’s where I would start.

I replaced it

Outdrive1 · May 11, 2025

crzy2bealive said:
View attachment 1505253
I replaced it

Looks good.

how about prop shaft seal? Are your bellows good? Do you have water in the bellows?

crzy2bealive · May 11, 2025

Outdrive1 said:
Looks good. how about prop shaft seal? Are your bellows good? Do you have water in the bellows?

Ok which one is prop shaft seal?

That’s the one directly behind the prop? That needs to be essentially drilled out.

If so, I did not because when I initial pressure tested and spun the prop shaft it did not show bubbles with soapy water,

No water in the bellows.

Outdrive1 · May 11, 2025

In the diagram, 57 and 58. One is designed to keep oil in, the other to keep water out. They are put in opposite directions. If you lose the outside seal water can get in. Fishing line can ruin them. It’s been years since I wrenched so trying to remember exactly.

crzy2bealive · May 11, 2025

Outdrive1 said:
In the diagram, 57 and 58. One is designed to keep oil in, the other to keep water out. They are put in opposite directions. If you lose the outside seal water can get in. Fishing line can ruin them. It’s been years since I wrenched so trying to remember exactly. View attachment 1505276

Yah I didn’t touch that area as the pressure test didn’t indicate I had leak’s there

Outdrive1 · May 11, 2025

crzy2bealive said:
Yah I didn’t touch that area as the pressure test didn’t indicate I had leak’s there

The pressure will hold the oil in and not show a leak if the outside seal is bad.

CCXHAL · May 11, 2025

Are you positive those bolts aren’t bottoming out?

crzy2bealive · May 11, 2025

Outdrive1 said:
The pressure will hold the oil in and not show a leak if the outside seal is bad.

Yah sounding like I need to do a vacuum test now that I’m tuned up,

crzy2bealive · May 11, 2025

CCXHAL said:
Are you positive those bolts aren’t bottoming out?

I been using this system for a while. But I could use stock bolts to rule it out

CCXHAL · May 11, 2025

Screw the bolts in without the cap. See how much remains.

crzy2bealive · May 11, 2025

Ok so it held 9 psi for like 2 hours on a pressure test.

Vacuum test I’m at about -6 psi for 20 mins has not moved.

Maybe this is how aerated oil looks like after it has been used.

I’m going to find a glass container and see how it looks in the morning.

It really could just be residual moisture from when I sealed the top plate incorrectly the first times

4Waters · May 11, 2025

crzy2bealive said:
Ok so it held 9 psi for like 2 hours on a pressure test.

Vacuum test I’m at about -6 psi for 20 mins has not moved.

Maybe this is how aerated oil looks like after it has been used.

I’m going to find a glass container and see how it looks in the morning.

It really could just be residual moisture from when I sealed the top plate incorrectly the first times

View attachment 1505305

I would say it's residual moisture,just leave that 6in of vacuum on for the night. If all is good in the morning fill it up, run it on the hose or take it back to the lake then drain and refill and forget about it, have fun this summer.

I had a little drive oil on the floor of the garage 9 years ago after sitting all winter 9 months after I rebuilt the drive myself. After I rebuilt it I pressure tested it overnight and it didn't drop at all so filled it and enjoyed it the rest of the summer. I drained the drive oil and pressure tested it again over night with the same results, I did a vacuum test over night and it was all good as well. I filled it up with fresh oil and ran it, it hasn't leaked since even with changing the drive oil every other season. Damned if I know

gqchris · May 11, 2025

I would have already ordered this a week ago

after being pissed off.

Sterndrive Engineering: For Alpha One® Gen II Sterndrive Applications

Fun Times · May 11, 2025

crzy2bealive said:
Ok so it held 9 psi for like 2 hours on a pressure test.

Vacuum test I’m at about -6 psi for 20 mins has not moved.

Maybe this is how aerated oil looks like after it has been used.

I’m going to find a glass container and see how it looks in the morning.

It really could just be residual moisture from when I sealed the top plate incorrectly the first times

Yes, that just looks like the usual residual moisture in which honestly takes a good number of oil changes to start to clear it back out to a normal color of the oil you're using...It doesn't look fresh and if it was leaking that bad right after all the work you have done, then usually the moment you pull the drain plug, clear water would come out first before the oil.

With the oil mentioned and just so you're aware that technically speaking, while oil is oil in the grand scheme of things to keep it lubed and still would work for you as many have used it as well over the years, the Premium gear lube you're using was more meant to be used in lower horsepower outboard gearcases vs most of the stern drives used today... The following is the breakdown of recommendations from Merc.

Mercury Precision Gear Lubes

Mercury 80W-90 Premium Gear Lube is recommended for gearcases for outboards below 75 horsepower. It outperforms automotive gear oil in marine applications by providing maximum protection against excessive wear in the presence of water and helps prevent corrosion and pitting.

SAE 90 High-Performance Gear Lube was engineered to extend gear life in high-speed and high-horsepower sterndrive and outboard gearcase applications. It contains extreme pressure synthetic additives to protect gears from metal-to-metal contact and provide excellent protection against corrosion and excessive wear.

85W-90 Extreme Performance Gear Lube is recommended for use in racing, high-performance and extreme-duty gearcase applications.

A Guide to Mercury Precision Marine Oils & Lubricants

Choose the right lubricant for your engine or gearcase. - Choose the right lubricant for your engine or gearcase.

www.mercurymarine.com

Often you can find the High-Performance Gear Lube too at Walmart for the lowest costs vs say a Merc dealer.

Alpha One Gen 2 Top Cap Leaking! Help!

Well-Known Member

Well-Known Member

Putting on the brakes

To The Rescue!

Well-Known Member

Well-Known Member

I will not let them take me🤣🤣

Well-Known Member

Putting on the brakes

Well-Known Member

Well-Known Member

Moderated

Well-Known Member

Well-Known Member

Moderated

Putting on the brakes

Moderated

Putting on the brakes

Well-Known Member

Well-Known Member

Outdrive1 Marine Sales https://www.outdrive1.com/

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Attachments

Well-Known Member

Putting on the brakes

Well-Known Member

Well-Known Member

I will not let them take me🤣🤣

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Outdrive1 Marine Sales https://www.outdrive1.com/

Well-Known Member

Outdrive1 Marine Sales https://www.outdrive1.com/

Well-Known Member

Outdrive1 Marine Sales https://www.outdrive1.com/

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Moderated

Mercury Precision Gear Lubes​

Mercury Precision Gear Lubes