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1955 Johnson 25 HP

N

newb

Member
"Hi all,

I have just purcha

"Hi all,

I have just purchased my first boat and motor! It is a 13'Jon Boat with a 1955 25hp. I am having a few problems. Here is what I have done.
Rebuilt carb w/carb kit
Replaced spark plugs
Checked compression while cold- 90 on both cylinders
The motor will start with much effort and shoulder pain. I do have to stay on the throttle to keep it running. After it has run it will start easily.
The round thing that mechanically links the throttle to the carb does not move until the throttle is nearly wide open.

Any help truly appreciated. Thanks"
 
that contact wheel needs to be

that contact wheel needs to be timed to just touch the metal cam when the throttle just reaches the "start" position. The cam has 2 small attach bolts. ( usually a 5/16" wrench) Loosen them and adjust the cam so the rubber roller makes contact as the throttle reaches the "start" position on the tiller control. What it does is set the carb throttle plate in time with the throttle for the most efficient starts.
The cam attach holes are slotted so it can be adjusted. Kinda tough to reach the bolts - but it can be done with little effort.
 
The throttle on the tiller wil

The throttle on the tiller will go from stop to start only and not all of the way to fast. Is this a linkage adjustment?
 
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cam adj.
 
There has to be a reason for t

There has to be a reason for that. You will have to do some looking and see what is stopping the travel
I have seen stiff old spark plug wires hold the armature plate from rotating.
Check the pinion and gear at the rear of the throttle shaft to see if the gear mesh slipped and is at the end of the gear tooth slots.
Look over this site - It may help you as many things are common to your motor.
"click and paste it"
http://www.duckworksmagazine.com/06/columns/max/index12.htm
 
The gear at the end of the til

The gear at the end of the tiller will slip if I apply too much pressure. When this happens I have to loosen the bolt and nut in order to realign the gear. I have checked the assembly and did not find any binding. Looks like the cam is bent where it meets with the cam roller. It is touching at stop and doesn't really move until it gets to start. Shouldn't it move gradually out from slow to fast?
 
It is hard to figure it out wi

It is hard to figure it out without seeing what is going on. Most of those motors had a lockout arm to prevent acceration - unless it was shifted out of neutral. It has to move from slow to fast in order to open the throttle plate on the carb to increase acceleration..
 
"The gears on the tiller slip

"The gears on the tiller slip when too much pressure is applied to open the throttle. If I manually turn the cam all the way it will go a bit further and the butterfly in the back of the carb will go about 3/4 open.

Is there an adjustment for this?

Without removing the flywheel and looking through the slot, the points are gapped at .02 and there aren't any cracks in the coil.

Should I pull the flywheel and look further?"
 
The tiller gears should not be

The tiller gears should not be slipping. There is enough teeth on the gear that the throttle will go from close to full open. If the gears slipped - it could be that the teeth are not meshed in the proper slot. There is a quick disconnect at the top of that vertical throttle shaft. Disconnect that and check with disconnected. Tiller throttle should move full travel and the stater plate can be checked to see if it moves freely through full travel.
You may need to order a maintenance manual and to go any further. The magneto portion needs to be set up correctly and the book would show you how to tune it properly..
 
If you are checking throttle t

If you are checking throttle travel in Neutral you will only get to Start or slightly beyond. Shift to Forward and see if it will travel to Fast. Resetting the carb may help with the hard cold start. Turn the low speed needle valve (top) in until it just seats and then out 1 1/2 turns. Set the high speed needle at 3/4 turn. After the motor starts adjust the low speed to get the best idle. This can be done in neutral. The high speed needs to be adjusted in gear and preferably under load.
 
joe do you have a trim and til

joe do you have a trim and tilt complete for 1990 johnson 200hp if so post with price pk lease or e-mail me
 
OK. I was able to fix the tiller gears from slipping and with the manual properly adjust the cam follower. The throttle will also go to full throttle when it is in forward as indicated above.

The motor is still very hard to get started. Any ideas? When it does start it runs well and starts easily after.

Thanks.
 
What type of oil are you mixing with the gas and at what ratio? Are you pumping the pressure tank before starting the motor?
 
I have the same brute but elec start. Its likely your spark is weak and when your pulling it over cold your not effective. I'd pull the flywheel and do a precise tune up. Clean or replace points. Set @ .020......no less. As stator hubs wear you will loose gap on firing cyl 'cause things are configured that firing coil pulls towards the flywheel just when points are at index. I'll send this and go on.
 
Now back off or set your replaced coils.....and they have been replaced I'm sure......at the back edge of the chamfer at top of posts. You don't want rubbing as filings will t-ferr to points and disrupt spark. If condensors don't have a rubber cap where wires come out I would replace them too. They may be still original. Its cheap insurance for hotter spark. I'll touch now on recoil improvements in next post.
 
The big twins are hard to pull and you may need to know my little trick. Pull out the starter cord until it stops and determine the minimum length you can work with. Shorten the cord and that will help by gaining mechanical advantage as the hub is in effect smaller diameter thus giving you more power to pull it over. I've even spooled with stronger but smaller diameter cord to do the same effect. Ok....good luck!
 
Wouldn't it be the other way around?? Wouldn't more rope give you a bigger diameter pulley and more mechanical advantadge???
 
Right on, spool to the top in this case. I'm glad someone is paying attention. The closer to the hub, the faster the motor will spin. I remember trying to get a faster spin on the little twins that were about worn out. Thanx for the correction. Tim
 
I checked the spark with a spark plug checker and seemed to have some spark.
I put some premix into the spark plug hole and got it to try to start. When the plugs were out they did not appear wet. Does low compression cause the hard starting? Would it run with low compression? I have read about using a decarbing product to possible bring the compression up.

Thank you
 
90 is pretty decent compression and i would still suspect spark. Do you have a flywheel puller? I would never trust these old motors without going over the stator plate. Many folks don't set things up correctly and weak or intermittent spark is the result. Your plugs may show you a spark but that doesn't mean it will run. I like to see a nice crackling blue colored spark. Check out your plug wires too make sure they are not worn and possibly loosing spark. If they are arcing to ground at the stator plate, however it is usually at higher speed when more voltage is being produced. Many times the wires are overlooked. A decarbonizing agent will not improve comp. unless there is a stuck ring that might get freed up in the process.
 
Low compression will make for more difficult starting and it will run with low compression but poor idle. With your comp. @ 90p.s.i. I think that is fine and your problem is elsewhere.
 
I just got the flywheel puller and will do this. What about the fuel delivery? I get a little grumbling like it wants to fire quicker when I put a little premix in the cylinder.

Thanks
 
Well maybe there is something with the low speed circuit or choke. I have had hard starting on these if the choke isn't fully closing. If it idles good once it starts, the low speed circuit is likely ok. Check some posts here for proper carb settings too and make sure your getting a full float bowl when you prime with the pressure button. Fill with your primer button until your finger hurts. Make sure the float level is properly set. Float should close needle valve as it becomes level with the upper carb casting.
 
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