sick 115 hp johnson

[wllrdmoor]

My friend has a 115hp johnson that takes a lot of cranking to get started and then it wont idle slow, after it warms up you can give it throttle and it will get the boat moving but it seems very gutless. We put an electric fuel pump on to be sure of enough gas. It has a weak spark but I dont understand the ignition system. It has no tach, 120 psi compression, new plugs, starter and battery seem fine, this motor has a jet foot instead of a prop. I suspect spark problems but I dont know how to test it out. Some ideas on this would would be greatly appreciated.

Willy

 

[the machinist]

Re: sick 115 hp johnson

You mention nothing about cleaning the carbs, this would be a good starting point.

How about the choke, is it functioning? If you are new to boating, push the key in to operate the choke.

Also with a jet unit, they need to operate at about full throttle, not anything like a prop.

 

[wllrdmoor]

Re: sick 115 hp johnson

Thanks for your reply, I dont think the carbs have been cleaned and you are right, the choke has to be manually operated which will be fixed later. This motor is on a 16' flat bottom aluminum boat and it seems to me it should be fairly fast even with a jet unit and it wont come close to a plane. I was thinking that at wot carb cleaning wouldnt be a issue.

 

[Solittle]

Re: sick 115 hp johnson

It will be an issue if it has crud inside.

 

[Daviet]

Re: sick 115 hp johnson

First remove the electric fuel pump. Then preform some basic checks, spark should jump a 7/16" air gap. Check the compression, what numbers do you get? If both of those are ok, I think it's time to overhaul the carbs.
You didn't post a model number, it would help to determine your ignition system.