1974 johnson 50 WOT trouble

[jetboat junkie]

Hello all, I am a new member. I am having trouble w/ my 50hp. I was searching old posts and found one labelled
{1974 50hp Johnson "Getting Frustrated"}. I am calling out to "jsalz" and wondering what finally fixed your problem. My 50hp is basically doing the same thing. I have done just about everything. Have replaced 1 carb, stator, fuel pump, fuel lines, plugs, lower seals, checked reeds. Have had boat for over a year and been on water twice (with troubles). Boat is at 3rd shop and mechanics are now guessing. Please HELP !!!

 

[Daviet]

Re: 1974 johnson 50 WOT trouble

What exactly is your problem?

 

[jetboat junkie]

Re: 1974 johnson 50 WOT trouble

Thanks for responding. well, just took it out 2days ago after mechanic replaced "bottom seal" ? it took off and ran good for about 2 minutes then RPMs came down like you backed off throttle and kinda surges. at idle you can rev motor and tell its high RPMs, but when its at WOT and not running good it sounds like about maybe 2k RPMs and barely on plane.

 

[Daviet]

Re: 1974 johnson 50 WOT trouble

OK, start with some basic checks, compression and spark. It would good if the compression was somewhere around 125-150 and within 10% of each other. The spark should jump a 7/16" air gap and be bright blue. That will tell you the basic health of the engine. It might be that you are going to have to do some testing in the water, use a timing light to check for spark under load to make sure you are not loosing spark on one cylinder. You can also remove the air silencer cover and squirt fuel mixture into each carb and see if it picks up for you.

 

[jetboat junkie]

Re: 1974 johnson 50 WOT trouble

ok. probably wont be until next weekend. meant to add that after last trip few days ago, mechanic is saying to replace the power pack. he thinks it might be getting hot. Hot ? after only 2 mins. Question- what type of issues is most common when power pack is going bad.

 

[Daviet]

Re: 1974 johnson 50 WOT trouble

Can drop one or both cylinders.