75' johnson 135 comp #'s .... opinions

[coolbikeguy]

ok i did this cold and i did it with all the plugs out and also taking 1 plug out at a time just to see if there was a diff. here are the#'s i got ..

cylinders 1 and 3 ....between 115 and 120 each

cylinders 2 and 4 ... between 90 and 95 each ...

so what should i do ? am i do for a bore ? are oversize pistons available ?? i have all winter to get this thing in tip top shape. all opinions appreciated. thanks guys, scott

 

[iwombat]

Re: 75' johnson 135 comp #'s .... opinions

1 and 3 look good.

2 and 4 may have a head-gasket issue, or stuck rings. But, they're not really all that bad. What do the plugs on 2 and 4 look like? How long since the last decarb?

 

[coolbikeguy]

Re: 75' johnson 135 comp #'s .... opinions

the plugs didnt look to bad. i dont htink any worse than 1 and 3 did. the last decarb ?? who knows. i just bought this ...

to get this ..

also got a bonus galvanized roller trailer and only gave 500 bucks for it. i was told it ran earlier this year but he said it over heated for some reason ?? hopefully the overheat didnt cause a problem.

 

[emdsapmgr]

Re: 75' johnson 135 comp #'s .... opinions

A freshly overhauled 135 with stock heads should have well over 130# compression. Check the head part numbers with a factory parts list. Before you tear into it, try a decarb on the engine with a can of Bombardier Engine Tuner. It's ok to repeat the decarb. I'll bet the compression will come up.

 

[mikesea]

Re: 75' johnson 135 comp #'s .... opinions

unless you see real discolorarion and burned wires.id bet your ok,but need to find out why it heated,if the motor was overhauled,i would think an impeller was done,the v4 s like you have .have the thermostats located in lower end of powerhead,in the housung that the 2 hoses hook to,therefore,they are not only a bit difficult to work on,but,debris like sand tend to settle there and can plug up thermostats causing overheat,but,hopefully it was a temporary problem from some floating debris,as for the compression,its not uncommon for 1 side to be differenht because over the yrs ,the head may have been shaved a bit,i honestly wouldnt be concerned,each side is whithin 5 lbs of its companion,perhaps you didnt crank the same amount,put her in the water and run it threw its paces.I think you will be fine,looks like a clean rig for its yr.

 

[coolbikeguy]

Re: 75' johnson 135 comp #'s .... opinions

i dont think the engine ever had an overhaul .. if what i said made you guys think that ... im sorry for the confusion. yea, the motor looks really clean. i maky give a new head gasket a shot and see what happens ... thats cheap enough, and i may also go ahead and get the thermostat out and test it and replace if needed. other than that the only other thing i can think of for the over heat prob is the impeller. is there a way to do a flush on the water system with out the engine running ? maybe try to clean out the water passages ??

 

[iwombat]

Re: 75' johnson 135 comp #'s .... opinions

You only have a single vernatherm (no t-stats) on that motor, and you'll probably need to remove the bubble-back exhaust cover to get to it. You can backflush the cooling system by putting a hose on the heads.