Johnson 135 horse prop help

[Mikeyboy]

I have a 1975 Johnson 135 horse motor and I am thinking about getting a new prop for it. The p/o told me they put on a 15p prop for a better hole shot while towing. It is a 3 blade steel prop. The boat is a 1969 18' Larson deep v hull. I have no clue what direction to go as far as a new prop. Size, pitch, material, manufacturer. Need help have no idea what I'm looking for.

 

[sutor623]

Re: Johnson 135 horse prop help

Well if you dont have speed/RPM's for us then we cant help. What is your WOT RPM reading with this prop?

 

[Mikeyboy]

Re: Johnson 135 horse prop help

I am not sure. One of the reasons I am considering a new prop is so I can cut this on down and use it as a test wheel as I am having problems tuning the motor. It has never run properly.

 

[sutor623]

Re: Johnson 135 horse prop help

Well before I'd do all that I'd order a tinytach and use a GPS. Find out your RPMs and all that jazz. I did a link and synch on my motor with the actual prop running in a HUGE test bucket so that I could tune the motor for Forward in idle. My motor have fixed high speed jets though, not too sure about yours.

 

[Mikeyboy]

Re: Johnson 135 horse prop help

Gotcha. How big of a bucket did you use. I bought a fairly large test tank but I don't want to mess anything up. I have idled the motor in it but never given any throttle.

 

[sutor623]

Re: Johnson 135 horse prop help

Well with that much HP you do NOT want to give it any throttle. You will kick all the water up and maybe even destroy your bucket I have a 55 gallon tub that I fabricated to fit my motor into. If you put the motor into gear while in idle, you will be fine for tuning. The first thing to do is to get the motor at factory idle, when in gear, in the test tank or water. This is the only accurate way to do it. Most of these motors have adjustable idle needles, and a fixed high speed carb jet. (Again, not sure about yours) Getting the ignition timing right on some older motors can be a real pain. What type of ignition system is on this motor? Distributor, ignition coils, points?

 

[sutor623]

Re: Johnson 135 horse prop help

Looks to me like you have ignition coils, stator, rectifier, power pack and timer base. Unless there is an issue with a misfire, I think your ignition system should be okay. If the timing is off, it may be a bad timer base. You cant adjust the timing on this motor, so that is a plus for ease of maintenance. I dont think you can adjust the idle speed either, looking at the chart on marineengine. May be a simple carb and fuel pump overhaul. It may also have a bad timer base. If you pull the flywheel, these things separate and sometimes melt from friction. All of the Shotty running johnsons that I have seen that have this type of ignition system have either had a bad rectifier or a bad timer base.

 

[Mikeyboy]

Re: Johnson 135 horse prop help

Thanks for the advice I'll look into that. I was planning on pulling the carbs next. I have a 240 gallon test tank, it's a feed trough I got at farm and fleet. It works pretty well so I can put it right behind the boat. It does make quite a mess when I put the motor in gear though.

 

[sutor623]

Re: Johnson 135 horse prop help

Yeah they normally do that. You can always fill the trough, put the motor on muffs, and put it in gear. That way if it does kick out a bunch of water you wont run the WP dry, not even for a second!