Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

[JimVmd]

Hello again,

As I was bottoning my engine up after gearbox re-seal, I noticed a distinct difference on the Sierra powerhead to exhaust tube gasket then what shows in the Johnson parts catalog.

The Johnson original p/n is 304314, Sierra's 18-2894.

Other than some minor slot differences (no concern) the major question is regarding the gasket over the water tube opening. On the Sierra, it is closed over. On the Johnson part detail, it has an opening as one would expect.

Is this right? I wouldn't think so. See diagram attached.

Surely you experienced hands have noticed. Should I just cut in the hole with a razor knife?

Regards,
JimVmd

 

[Chinewalker]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

Not sure where you got the photo of the OEM gasket, but that is NOT correct. It doesn't show the opening for the lower seal assembly that sits atop the driveshaft. The Sierra pic looks correct to me.

 

[HighTrim]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

yeah, I just went down and looked at my stash of 304314 gaskets, and it does not have the hole cut out, it looks like your Sierra gasket.

 

[JimVmd]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

Not sure where you got the photo of the OEM gasket, but that is NOT correct. It doesn't show the opening for the lower seal assembly that sits atop the driveshaft. The Sierra pic looks correct to me.

The OEM pic was clipped off my 1957 Johnson Motors Parts Catalog Models AD-ADL-11 7.5 hp Final Edition part no. 377019. I don't know where I can get a more reliable picture of the original Johnson Gasket!

The OEM, as pic shows, has a hole in the gasket directly on top the watertube as it comes out the exhaust housing/cover assembly. Hole matches hole between the exhaust tube and the head, and the Sierra gasket blocks it. All else is good.

I've ordered the Sierra part twice, and got the same gasket from two sellers. "= Johnson 304314" but not!

So what do I do, just cut the circle?

Thanks all,
JimVmd

Oh by the way, if anyone needs one of those precious Johnson medallions for this or like same, a guy has them up on ebay item 261322242976 showing one left right now

 

[nwcove]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

i have a couple of the omc gaskets, both are as mentioned above, same as the sierra part. i can post a pic if ya like!

 

[HighTrim]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

He has been selling them for years. It is not the last one

He gets them made in China.....still a decent medallion, I have seen them, but most definitely not bought from the wife of the engineer that made them. That is just his story.

 

[Chinewalker]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

The hole in the water passage area of the OEM pic is irrelevant as the pic of the gasket is just plain incorrect. The actual gasket looks nothing like that, OEM or otherwise. The OEM one looks like the Sierra one.

 

[JimVmd]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

The hole in the water passage area of the OEM pic is irrelevant as the pic of the gasket is just plain incorrect. The actual gasket looks nothing like that, OEM or otherwise. The OEM one looks like the Sierra one.

Ok!, I'll leave her alone. The Sierra is installed. The motor runs as it should, and I get warm water out the exit.

I'm done with it, except for receipt of the medallion from a friend that is sending me one. lol Chris! He will die when I forward this post. I told him a hundred more may go up on ebay after that last one is sold.

Thanks guys,
Happy here with the AD-11. Starts one pull, runs low idle, pumps up like a Harley on a wrist twist, cools itself and ready to run. Just needs the Chinese medallion installed and a little touch up spray and I'll post pics!
Replaced stator plate (stripped point set screw), put all new ignition in on the plate, new plug wires and plugs. Replaced impeller, and seals in lower unit. Good for another 50 years. Now need a vintage aluminum boat worthy of the '57.

 

[HighTrim]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

You will like the medallion, they are well made, and much better than a cracked one!

I think he get amusement out of all the emails he gets

 

[F_R]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

From my 1957 7.5hp parts book. The one you posted is a real head scratcher, I've never seen one like it.

 

[JimVmd]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

That is a headscratcher here too F_R. I'll affix my whole parts book .pdf scan later for your inspection. I have it in hardcopy at home, a .pdf at work machine. My hardcopy looks original, with staples and 3-holed, even yellowed with age.
Regards,
JimVmd

 

[JimVmd]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

From my 1957 7.5hp parts book. The one you posted is a real head scratcher, I've never seen one like it.

Attached is part of my manual. Cover, and pages 8 & 9.

Very interesting that we have two different diagrams completly. Your gasket is shown with the lower unit group and mine is shown with the powerhead group. Definitly two distinctly different gasket sketches and pages!

So I guess I'm going to next learn that my hardcopy which looks very unsuspectingly like a real manual is another good Chinese knock off?

 

[Chinewalker]

Re: Powerhead Gasket for 1957 AD-11 7.5 hp Johnson

Not saying your diagram isn't original, but it IS incorrect in the representation of that particular gasket. What gets me is that your OEM diagram's gasket isn't even close! That whole forward portion of the gasket is completely wrong. Correct outside shape, but the inside configuration is completely wrong and doesn't make any sense. The water passages are incorrect, there's no clearance around the driveshaft hole for the lower seal, etc.

Those diagrams were hand-drawn back then. It's entirely possible the artist had the wrong info at hand to work from with your particular manual. I have the '56 version handy it it shows the same gasket Frank's diagram shows. It IS the correct one, as you've discovered.

In any case, glad you got 'er running! Those 7.5s are one of the better motors you can find. As long as you run them fat on oil they'll keep right on going. I've got '55 Evinrude, '56 Evinrude, '57 Johnson and '58 Johnson versions. I think the '55 is my fave, due in large part because it's the one my Dad and I put together from a box of parts about 30 years ago. Needed a powerhead transplant about 20 years ago when one of my brother's inadvertently skimped on the oil, but it's still residing on the boathouse motor rack, awaiting another season.