55hp Johnson almost there!!

[EJ3]

A little history on my 1977 55hp Johnson first...

Items replaced with new (in order):

Starter Solenoid
LU oil changed
Spark plugs
Ignition switch
Rectifier
NEW, not replacead, Tach
Carb kit
***And 1 coil, so far***


Before I replaced the coil it would do 5500rpm @ WOT until it ran hot, then only run 3000rpm at WOT. I replaced 1 coil, as the spark plugs were indicating only one was the problem.

After the new coil, the next time on the water it ran 5500rpm WOT for 15 +/-minutes, that was the amount of time it took to get to our destination for fishing. Absolutly no signs of problems at this time. On the way back to the ramp the same problems as before were happening.

I am going to replace the other coil, since it is only $40 and as old as the other replaced coil, as I think it might be my problem.

What do you guys think?

 

[tashasdaddy]

Re: 55hp Johnson almost there!!

you don't mention rebuilding the water pump. there is a reason it ran hot. they loose rpms, as the metal surfaces are binding, running hot.

 

[EJ3]

Re: 55hp Johnson almost there!!

Oops, sorry. I purchased a water pump kit and went to install it when I noticed they gave me the wrong kit.

The seller (I have only had it a few months) said the impeller was changed recently, but I wanted to change it anyways. I inspected the current impeller and compared it to the new, but incorrect, one and it seemed to be in the same condition (nice and flexable/rubbery, not dry or cracking). So I figure the seller was not lying when he said it was just replaced, so I kept it in there. I do have warm water exiting the motor from the center of the prop and out of the exhaust holes.

So I took this as a good sign that I could use the current water pump and replace at the begining of next season.

 

[tashasdaddy]

Re: 55hp Johnson almost there!!

could also be time for a new tstat, poppet valve. when i do a tstat, i do all of it. especially if it is a salt water motor. while the stat is out flush the system with a hose.

 

[EJ3]

Re: 55hp Johnson almost there!!

Thanks for the advise, I will be picking up a tstat as well now!!!

 

[tashasdaddy]

Re: 55hp Johnson almost there!!

get the poppet also, as the can distort after running hot.

 

[EJ3]

Re: 55hp Johnson almost there!!

What is the poppet?

 

[HighTrim]

Re: 55hp Johnson almost there!!

The pressure and temp controlled cooling system contains the pressure valves (poppet), springs, and t stats. The circulation of water through the cooling system by the water pump (impeller) is controlled by the balanced action between the pressure control valves(poppets), water pump pressure and the t stats. When the power head and cooling system temps reach around 145 F, the t stats open, allowing heated water to pass through the water discharge. As engine speed is increased, water pump pressure opens the relief valves. This bypasses the t stats, allowing the engine to run cooler when it is running at higher speeds. They will be located beneath the t stats.

 

[Lakester]

Re: 55hp Johnson almost there!!

hello~

" As engine speed is increased, water pump pressure opens the relief valves. "

i was thinking of asking the same type of question.

thanks hitrim. you know... i have read, reread and studied my oe service manual numerous times trying to better understand this type of system. i knew it mixed and recirculated the water depending on temps, but wasnt sure why it did all this... book says..." keeps ideal... for all temps, all water conditions."

so now as i think i understand it now... low speed, thermostat set for 145F keeps engine warm and lets warm up. engine heats up, vernatherm system changes, and routes in cooler water, allowing warm, cool or blended temps to keep ideal running temps. it not only provides hot, and colder, but blended.

here is some info i researched on theory:

http://www.rostravernatherm.com/animations.htm

well, good. this will help me to better understand the system on my '71 85hp evinrude when i get into it.

thanks ej3, glad u asked that question.

regards

lakester

 

[HighTrim]

Re: 55hp Johnson almost there!!

Your motor has a recirculating cooling system where the water pump supplies water to the powerhead through the copper water tube via the water intake. The water then circulates in the powerhead and absorbs heat from the outer wall surrounding the steel cylinder, and the cylinder wall itself, which in turn is directed to the tstat. If the tstat decides the water is at the right temperature it will open, allowing the water to be discharged and replaced with cool fresh water from the impeller and intake.

However, if the water is not warm enough, the tstat stays closed and the increased pressure forces the poppet off it's seat causing the water to go back down through the second pipe to the water pump, where the pump recirculates it back up to the powerhead, constantly recirculating until it gets hot enough to open the tstat. The thermostat is constantly monitoring the water temp, opening and closing as necessary to maintain ideal water temperatures.

That is what your manual was referring to, just in more detail Lakester.