Compression for 58 Johnson 10 hp?

[cron78]

I have a ’58 10 horse Johnson that has been in my garage for a few years and now I want to get it running.  Compression check today read 70 psi in top and 68 in bottom.  That seems a little low, but is it too low to keep working on the motor?  I certainly need more experience with these old 50s OMCs, so if nothing else this is a chance to learn as I go.  Should I keep my hopes up or abandon it for parts?

BTW, I looked through pages and pages of search attempts in the AOMCI forums to find this answer and kept getting sidetracked into other topics for hours.  Now I need to get out there and remove the lower unit so I can learn how to do an impeller change on this motor, so I’ll sign off for now and check back later.  I’m curious to see the spacer tube on top of the impeller housing that I haven’t seen on any of the other (smaller) 50s motors I’ve tinkered with.

[Bob Wight]

My ’58 10hp runs about 85psi in both cylinders.   If yours has been sitting for some time, you might just have some stuck rings or maybe a bad head gasket.   I wouldn’t give up on yours just yet without some more investigation.   Post your questions here as you go – lots of folks will be glad to help out.

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."

[crosbyman]

Johnson Gear Case Parts for 1958 10hp QD-19 Outboard Motor (marineengine.com)

 

those comp#s should not stop you… drop some  light lubricant in the cyl and soak a bit .  place  both cyl mid-way to close the ports while it soaks .

 

you do know about the shift linkage bolt  you must loosen to drop te GC

Joining AOMCI has priviledges 🙂

[cron78]

Dropped the lower unit.  Both o-rings on the spacer tube on top of the impeller housing are rough and I will replace them.  There also isn’t an o-ring at the top of the drive shaft so I’ll get one for it, too.  Are there generic/industrial o-ring sizes that are matches for 301967, 302035, and 303067.  Just wondering even though I will probably go to the local marine shop to support them.  They have usually been able to get parts if they don’t have them in stock.

I forgot to check the gear oil before I removed the lower unit.  I’ll do that next.  Should I be able to change forward/neutral/reverse by hand by moving the shift shaft?

[Phil Budne]

OMC never published numbers for compression. I have a 1960 Johnson (all of this applies equally to Evinrude/Johnson 10hp engines of the 50’s and 60’s).  1958 is my favorite year for Johnson styling (grew up in an Evinrude family, but the marina where we put our boat into Lake George was a Johnson dealer, so saw a lot of them on their rental boats).  When I first got mine it was around 70 in both holes and ran, it came up to 75/78 after running it a couple of times.  A note I have of a post by Gary, an esteemed older member is that they’re hard to start below 70PSI.

A couple of weak points to watch out for:

The piston pin can put wear on the top end of the (plain bearing) rod, causing “rod knock”; To check, take out the plugs, and rotate until each pistons is starting to go down, put a dowel through the spark plug hole and push down on the piston and see how much it can move down (without moving the crank/flywheel).  At some point in the 60’s (62 or 63?) they made the rods stronger, and used a larger pin with roller bearings: A set of pistons/rods from the later engines can be swapped in.  Best to  oil at 24:1 without the roller bearings!

1958 and later switched to the smaller/weaker 5.5/7.5 hp lower unit;

The drive shafts are hard to find.

I seem to recall hearing the bottom bushing in the tower can wear and become egg shaped.

 

http://www.omc-boats.org
http://www.aerocraft-boats.org

[cron78]

Gear oil came out 90% green and clear (don’t know what brand, the Yamalube and Johnson gearcase lube I have are both clear amber) but there was a bit of cloudy medium brown that drained at first from the bottom.  Should I be alarmed?

Neither drain screw has a gasket.  The Marineengine.com diagram for the 58s seems to show gasket(s) for the drain plug(s) but the catalog list doesn’t list either.  Do I trust the drain port machining or should I add gaskets?  If so, what gaskets?

Thx

[cron78]

Thanks, phil.  I have several Johnson and Evinrudes from the 50s and 60s from 3 hp up to 40 hp, plus a ’35 fisherman and a ’47 Sportwin.  The 1958 Johnson color scheme is my favorite, too, by far.  I rarely have time to get them running and therefore have only had a couple on the water.  I plan to spend more time, though, and have more fun with these old (hopefully) smoke makers.

[cron78]

Oh, and I forgot to mention that I’ve met Gary at a few meets down here in Florida.  We miss him down here!

[Fastwin18]

Mine has a compression of 77 and 78.
Starts first pull and runs and a idles great.

[Bob Wight]

You definitely need to install the required seal washers on the gearcase drain and vent screws, original OMC part #304083.

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."

[Author]

Posts