Compression for 58 Johnson 10 hp?

[cron78]

thx

[labrador-guy]

cron as others have stated these 10hp OMC motors use the small gear case from the 5-1/2  7-1/2 motors. Understand that these motors need special attention.  The gear case oil needs to be changed often and keeping water out can be a challenge.   If you live in an area that freezes, drain the oil out at the end of the season.  Fill it with good clean 90weight.  The fill/vent plugs need gaskets.

dale

[jeff-register]

With someone not putting seals on the drain / fill ports no telling what oil/fuel mix you motor has seen. Like others stated soak thu exhaust ports & use a small flat screwdriver to ,ightly push on the rings to see if they are stuck. My 58 Johnson ran very well on 75 compression & got better with proper oil/fuel mix with quality myl. I would replace the top cramkshaft seal to, my magneto looked like sprayed oil when I first got it.I used a tiny drill bit & made a hole in the seal metal 180 degrees out & used a drywall screw to get removal & grease to catch all the metal shavinge

[MIKE SIMS]

While a gasket did not come off with the fill / drain screws I have seen some that the gasket sticks to the gear case and blends right in to disappear. So check with a pick but don’t scratch the sealing surface.

[jeff-register]

So true Oldlure!! Specially with my old eyes.

[cron78]

Thanks, Oldlure.  I’m staring at bare metal on the screw and the seat.  I picked up the drain plug gaskets today at the local marine joint, along with several other items they had in stock.  Will be back at it this weekend.

How important are the gaskets on the access port for the shift linkage joinery?  What came off is shot and I can’t find a source for new ones.  If they are needed, I can try to learn how to make my own.  What kind of gasket material sheet should I be looking for…cork? Something else?

[Bob Wight]

The gasket on the shift linkage access door will prevent oil/water exhaust from leaking out onto the housing and making a mess.   You can make your own from Fel-Pro Karropak or Cometic fiber gasket material – either should be available at your local auto parts store.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1957 Evinrude 3022
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."

[fleetwin]

Perhaps I have not read this thread completely.  Keep in mind, the round drain screw seal washers could indeed be stuck in the gear housing cavity, which is normal and OK.  You don’t want to use two gasket/seal/washers though.  I would have another look inside those housing cavities with a pick to see if the washers are stuck in there.  Replace the washer/seals for sure, but make sure the old ones are removed from the housing, two washer seals can create a leak as well.

The correct part number for the OEM replacement washer/seals is:  311598.

Replace those other orings as well, use the OEM pieces, even though they are expensive.  Be sure to lubricate the driveshaft splines properly with the OMC moly lube as well.

PS:  those compression numbers seem “OK” for this engine.  Your compression gage might not be accurate as well.

[cron78]

Thanks Bob and Fleet.  I will be back at it this Friday.  Gonna go find some gasket material and learn how to make replacements for 305299 (and 304023 and 305263).  Anybody have any thoughts on the $10 hollow punch kit from Harbor Freight (I really don’t like buying the Chinese stuff, though)?

Cron

[fleetwin]

What gaskets are those??

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