1960 40 hp johnson seahorse ( Compression )

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blue88gt

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I have a 1960 40 hp Johnson seahorse, i checked the compression, and it has 90 on top and 80 on the bottom, is that enough compression for that motor..??? it idles fine,but has no top speed.. the engine wasnt used in about 6 years.. i tryed using sea foam but mad no difference..
 
tashasdaddy

tashasdaddy

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Re: 1960 40 hp johnson seahorse ( Compression )

carb cleaned and rebuilt, new gas adjustments accurate, good spark?????? see the top secret file. 1st theard in this forum
 
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blue88gt

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Re: 1960 40 hp johnson seahorse ( Compression )

i never cleaned the carb or anything, before i put anymore money into it i want to know if 90 and 80 pounds of compression is good..
 
bktheking

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Re: 1960 40 hp johnson seahorse ( Compression )

As best that can be expected for a motor that hasn't run in 6 yrs, should start if everything is in order, carb, water pump, spark etc etc.
 
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blue88gt

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Re: 1960 40 hp johnson seahorse ( Compression )

the motors runs good, just dont have very good top speed..
 
bktheking

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Re: 1960 40 hp johnson seahorse ( Compression )

The carb is probably full of junk, got spark on both plugs? I bought a 1964 40 hp that hadn't run in 2 yrs and had to clean and adjust the points, clean the carb, do a link and sync, replace the water pump and change the plugs before it would run right. Your motor is probably going to need some attention before it will run properly, 6 yrs is a long time without use to gas it up and go, especially if it wasn't put away properly.

Check the easy stuff first, these motors will have no power firing on 1 cylinder, they idle nice on 1 cylinder, it's to trick us owners. Then clean the carb, it's a must.
 
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jdsgrog

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Re: 1960 40 hp johnson seahorse ( Compression )

clean the carb as everyone says. also, does the carb have two needle valves? if spark is good on both cylinders and it starts fine, it's likely a carb issue. if there is a high speed needle valve, adjust it according to the "top secret file". when i adjusted my '67 33hp, my top speed jumped from 22mph to 27mph.

one other thing, your compression may change after you get the motor running for a while. something else that will increase compression is a decarb of the motor with seafoam. again, look at the top secret file.
 
lindy46

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Re: 1960 40 hp johnson seahorse ( Compression )

blue88gt said:
I have a 1960 40 hp Johnson seahorse, i checked the compression, and it has 90 on top and 80 on the bottom, is that enough compression for that motor..??? it idles fine,but has no top speed.. the engine wasnt used in about 6 years.. i tryed using sea foam but mad no difference..
Click to expand...

How did you test compression? With the pull start or the electric start? Did you pour some Seafoam into the cylinders and let it soak overnight? That will help free up stuck rings.
 
1946Zephyr

1946Zephyr

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Re: 1960 40 hp johnson seahorse ( Compression )

That compression is kinda low for a three ring motor with the compression releases. Then again, the compression releases might be why your readings are low and different between the two. Did you test with the hand starter or with the electric starter? If you're using the hand starter, then you'll want to unhook the compression release lever, from the hand starter assembly, in order to get an acurate reading.:cool:
 
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R.Johnson

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Re: 1960 40 hp johnson seahorse ( Compression )

1946 Zephryr: Let's try my guage
 
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mungo

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Re: 1960 40 hp johnson seahorse ( Compression )

bktheking said:
The carb is probably full of junk, got spark on both plugs? I bought a 1964 40 hp that hadn't run in 2 yrs and had to clean and adjust the points, clean the carb, do a link and sync, replace the water pump and change the plugs before it would run right. Your motor is probably going to need some attention before it will run properly, 6 yrs is a long time without use to gas it up and go, especially if it wasn't put away properly.

Check the easy stuff first, these motors will have no power firing on 1 cylinder, they idle nice on 1 cylinder, it's to trick us owners. Then clean the carb, it's a must.
Click to expand...

Hi BK and all-----what are the implications caused by running this (or any other twin cylinder) with just one cylinder working---what damage will be caused? ie.--if one cylinder cuts out when you are a long way from the ramp and you have to drive it back. cheers
 
bktheking

bktheking

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Re: 1960 40 hp johnson seahorse ( Compression )

None really, I've had a bank on my v4 cut out and I had to run it back to the dock about a mile out, when they are down a cylinder (or 2 in my case) they won't rev fast and have no power to plane out the boat but it's something you want to attend to before taking it out again. Just take it slow and don't beat the motor to death and it will be fine. As an alternative a kicker is always nice for a backup just in case.
 
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