1958 Johnson Seahorse 10 HP QD - 19

[Wayne.McC]

Long story short version, Bought boat, motor, trailer. Motor starts and runs, noticed wet plugs, no power. Rebuilt carb, set points .020 set plugs .030 starts, runs, idles, smokes, power loss, wet plugs. Fuel 24-1, plugs AC M44C also new plugs NGK J6C, no difference. Points coils condensers look new. Water pump and lower work good.
Question....
I suspect I need a powerhead rebuild. What do you think?

 

[jbjennings]

Re: 1958 Johnson Seahorse 10 HP QD - 19

Have you checked compression? If not, why would you suspect a powerhead rebuild? Almost invariably with the 50's motors the problem with no power is bad spark. Have you checked the spark with an airgap tester? If spark won't cross a 1/4" air gap or more with a hot blue spark every time, then your problem is bad spark. Wet plugs is a good indication of bad spark.
You really need to check compression. I suspect it will be around 80-90 psi if it's in good shape, but even pressure is the best indicator since gauges are often not accurate.
Milky plugs would indicate a blown head gasket.

Basically, I think your engine has bad spark, if compression is within 10% of one another.
One more thing---how do you know there is a power loss? Did it ever run good?
Good luck,
JBJ

 

[codykoke]

Re: 1958 Johnson Seahorse 10 HP QD - 19

I would suggest a compression test. Both cylinders should be close to the same. Are there any definite signs of power loss when running, if not could have wrong prop and running in wrong rpm range

 

[Daviet]

Re: 1958 Johnson Seahorse 10 HP QD - 19

You need to run champion plugs in it.

 

[kfa4303]

Re: 1958 Johnson Seahorse 10 HP QD - 19

Hi Wayne. Welcome to iboats. I used to have a QD-22 which is virtually identical to your motor. If the compression is ok (+80 psi with both cylinders whith in 10% of each other), then all the rest can be fixed pretty easily. A tune up kit with new points and condensers is only about $20 and a carb kit and lower unit seal kit are also about $20 also. You can everything you need right here at iboats too. Daviet is also right about the plugs. You want to run Champion J6C plugs. Once you've confirmed compression, I would pull the flywheel and clean/reset the points to .020", then rebuild the carb and she should fire right up. Make sure you only run it in a test tank with water filled up to about an inch or two below the main exhaust port. Here's a great link that can walk you through and enter tune up from top to bottom. Holler if you get stuck.

http://www.sschapterpsa.com/ramblings/johnson_QD.htm

 

[Wayne.McC]

Re: 1958 Johnson Seahorse 10 HP QD - 19

Compression check worm indicates just above 0 psi in the top, 35 in the lower. I'm pulling the head cover tomorrow.

 

[Wayne.McC]

Re: 1958 Johnson Seahorse 10 HP QD - 19

I will, Thanks, Bad reading for compression, pulling cover tomorrow.

 

[Wayne.McC]

Re: 1958 Johnson Seahorse 10 HP QD - 19

You are right on, compression bad, pulling cover tomorrow. Thanks

 

[Wayne.McC]

Re: 1958 Johnson Seahorse 10 HP QD - 19

About 4 MPH on the lake, no high end speed, compression test failed, 0 psi in top 35 psi bottom. Thanks I'm getting there.

 

[bbstacker1]

Re: 1958 Johnson Seahorse 10 HP QD - 19

With those numbers I'm surprised it would even run. You might want to try another compression tester.

 

[Wayne.McC]

Re: 1958 Johnson Seahorse 10 HP QD - 19

I didn't see this post before. the tester is out of the package, borrowed of corse. Pulled the head today, see reply to Chris. Input is always appreciated. Thanks

 

[jbjennings]

Re: 1958 Johnson Seahorse 10 HP QD - 19

SOmething is wrong with the compression test. THere's no way it would possibly run with 0 in one cyl., and 35 in the other.
The difference in cylinders does make it sound like you need to pull the head, but before wasting a head gasket I'd use another gauge and check it.
JMO,
JBJ