Topic: Powerhead to lower unit gasket, 5.5 Johnson – Antique Outboard Motor Club,Inc

This topic has 15 replies, 7 voices, and was last updated 6 months ago by aquasonic.

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May 17, 2024 at 3:24 pm #287824
Buster
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US Member
I’m replacing the water pump on my 5.5 hp Johnson. I’ve got the kit, including a new gasket for the powerhead to lower unit junction. Would members recommend I use a gasket dressing (I’ve got Indian Head gasket shellac) or should I just clean both flanges and bolt these together with the dry new gasket (no shellac)?

This is an opinionated question but I’d like to hear your thoughts.

Buster
May 17, 2024 at 5:19 pm #287828
bobw
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US Member
Yes, I use a gasket sealer on the powerhead base gasket, typically Permatex Aviation #3 sealer. The Indian Head product should work fine.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

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Buster
May 18, 2024 at 8:35 am #287832
labrador-guy
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US Member
Everyone has an opinion! For me, I coat that base gasket with oil when I assemble the powerhead to the leg. These 5.5hp omc motors sometimes can be a problem getting the gearcase and water pump set up right. Causing several power head removals. If you use sealer you will need a new gasket every time you pull it apart. JMHO

dale
May 18, 2024 at 10:33 am #287834
crosbyman
Participant
Canada Member - 2 Years
never did use sealer myself…actually I reused the gasket if not broken.. a small exhaust leak would not matter much and a water leak would drain down anyway.

up to you but as JHMO said !! If you use sealer you will need a new gasket every time you pull it apart.

Joining AOMCI has priviledges 🙂
May 18, 2024 at 10:10 pm #287843
fleetwin
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US Member - 2 Years
I usually just coat both sides of the new base gasket with grease… Can’t hurt to use sealer though, but it should be relatively light/thin, no need to make a mess and plug up passages
May 19, 2024 at 3:23 pm #287847
Buster
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US Member
Crosbyman,

I like your rationale. I’m going with no sealer. A small leakage here would be hardly noticeable and it would make a subsequent removal much easier. Though I intend to have a perfect assembly the first time, it doesn’t always work out that way.

Buster
May 19, 2024 at 8:20 pm #287853
Tinman
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US Member
I’ve never used a sealer and never had any problems.
May 20, 2024 at 6:53 pm #287873
aquasonic
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US Member
fleetwin wrote:

I usually just coat both sides of the new base gasket with grease… Can’t hurt to use sealer though, but it should be relatively light/thin, no need to make a mess and plug up passages

I used to use gasket sealer, but after destroying countless base gaskets that were installed with gasket sealer, I now use just grease. By using grease, you will most likely be able to reuse the gasket next time you remove the powerhead. Don’t use anything harder than aluminum to clean the mating surfaces to avoid scoring them.
May 22, 2024 at 12:29 pm #287902
Buster
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US Member
Antique Outboard Friends,

As an addendum to this project, I was curious about the water circulation pattern on these engines. The bulk of the cooling water enters on the throttle side, circulates through the power head and exits on the shifter side. I did notice a small, machined passage, shown on the attached photo. This would allow a small amount of the return water to exit into what I’ll call “shaft alley”.

Can anyone tell me the purpose of this feature, as it applies to the water circulation scheme? I’m continuously impressed by the smart design features of these ’50’s vintage engineers in their products. Slide rule guys knew their craft.

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fleetwin
May 22, 2024 at 1:25 pm #287904
fleetwin
Participant
US Member - 2 Years
Most likely there to add a bit of a spray to the upper exhaust are in the housing to help keep that cool. Although I’m wondering why it seems to be directed towards the driveshaft. Your driveshaft splines are lookin kind dry, better remove the seal assembly, check for proper orientation, replace the oring in the carbon seal and the round gasket up top…

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Buster
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