1998 Johnson, 25 hp, 2-stroke, dies at full throttle

[Ppopps]

Ok, here are the symptoms of my 1998 25hp Johnson, 2 stroke, tiller, I'm thinking either bad hose or bad fuel pump but you tell me. Had the boat out last weekend and ran it wide open in rough water for a good hour or so with no issues at all, ran perfect. This was also the first run of the year (5 months of winter here in Canada) on last year's gas that had been "stabilized" in the fall. Then, out this weekend just tinkering around with my son, it ran fine on the way out to the fishing hole, but to come home as soon as I opened it up it would cough and die after 5 seconds. I could always start it again and it was fine idling or at low speed, but twist her up and she dies. I then noticed that if I squeezed the primer bulb when she was about to die the bulb was not hard and motor would come back to life, so clearly it is starved of fuel? I read about a similar problem here and someone said to check float bowl for contaminates and sticky needles and all the rest but wouldn't the fact that squeezing the primer fixed it mean that's all ok? I have a spare hose I can try easy enough on the next outing, is there anyway to actually test the fuel pump? I pulled the fuel screen/filter and it was clean. I don't want to start ripping different parts of the motor apart if I don't have to....would like to go at it methodically thus asking for opinions, thanks.

Ppopps

 

[Rick.]

Re: 1998 Johnson, 25 hp, 2-stroke, dies at full throttle

You can take the fuel line off the carb and pull the rope and insure it is moving fuel up the hose. It sure sounds to me like your already on the right track
IE: the pump. Sure doesn't sound like your hose is at fault. Best of luck. Rick.

 

[Ppopps]

Re: 1998 Johnson, 25 hp, 2-stroke, dies at full throttle

You can take the fuel line off the carb and pull the rope and insure it is moving fuel up the hose. It sure sounds to me like your already on the right track
IE: the pump. Sure doesn't sound like your hose is at fault. Best of luck. Rick.

Thanks Rick, what do you think about my argument that if squeezing the primer fixes the problem that I shouldn't tear the carb apart? I mean, if there was dirt or something stuck in the float bowl that was keeping the fuel pump from being able to supply fuel, that wouldn't change by squeezing the bulb would it? I'll try what you say and pull the line on the carb and then turn the motor over. Just out of curiosity, I can see the butterfly plate, seems the air intake to the carb is totally open, I'm used to carbs on cars having air filters, is this thing supposed to look like that or am I missing a filter/flame arrestor?

 

[jbjennings]

Re: 1998 Johnson, 25 hp, 2-stroke, dies at full throttle

THere's no air filter on 'em. I guess they figured there weren't any dusty roads out in the lake.
ANyway, pull your hose off the carb---the one coming from the fuel pump and put it in a can or something. Now get a neighbor to pull it over and see if fuel pulses out of the hose. IF so, your pump is likely o.k.
Is your tank vent open? If the pump doesn't pulse some good gushes of fuel, that's your problem, if not, try your different hose and if still no go, then take the tank fitting off the hose and stick it in the filler hole on the tank and see if it runs good then. If so, there may be a crack or hole in the tank pickup tube.
Just some ideas,​

JBJ

 

[Ppopps]

Re: 1998 Johnson, 25 hp, 2-stroke, dies at full throttle

THere's no air filter on 'em. I guess they figured there weren't any dusty roads out in the lake.
ANyway, pull your hose off the carb---the one coming from the fuel pump and put it in a can or something. Now get a neighbor to pull it over and see if fuel pulses out of the hose. IF so, your pump is likely o.k.
Is your tank vent open? If the pump doesn't pulse some good gushes of fuel, that's your problem, if not, try your different hose and if still no go, then take the tank fitting off the hose and stick it in the filler hole on the tank and see if it runs good then. If so, there may be a crack or hole in the tank pickup tube.
Just some ideas,​

JBJ

All good info, I follow. Yes the vent is open on the tank....