Johnson slips/cavitates after 35 minutes

[ob]

Re: Johnson slips/cavitates after 35 minutes

Just to add another tidbit to the good help you are recieving,with the engine not running,the fuel primer bulb should pump up firm and hold.If the bulb won't do this then there is a leak in the fuel hose or fittings,the carb needles are not seating,or the bulb itself is defective.Once you install the new ones mentined above,see if it will pass this test.

 

[walleyehed]

Re: Johnson slips/cavitates after 35 minutes

Good advice....

 

[swade28]

Re: Johnson slips/cavitates after 35 minutes

I replaced the bulb. It does not get hard. I am in process of replacing the hoses. On my set up from the sending unit the hose goes to the bulb which goes to water separator filter then that goes to an inline fuel filter then to the engine to the filter there. This is how it was when i bought the boat. Should I get rid of some of this? Scotty

 

[ob]

Re: Johnson slips/cavitates after 35 minutes

Well you coud at least bypass the separator and any other auxiliary filters for now to see if leaks are an issue and then restest to see if the bulb will pump up firm and hold.

 

[Solittle]

Re: Johnson slips/cavitates after 35 minutes

You posted "it only does it at 3800-4000+ RPM runs fine anything less than that. But it will be going along and starts to pulse you can feel it start surging forward/back repeatedly". That sounds like some crud in one or more of the carbs to me. Whay do the plugs look like? - thinking if you have a bit of crud in a carb it should show up on a plug.

 

[swade28]

Re: Johnson slips/cavitates after 35 minutes

OB. I replaced most of the hoses and same problem. I started closing off different places in the system and finally found that the inline fuel filter seemed to be leaking. About 4-5 months back it seemed this problem started to happen and i could smell fuel. I noticed the hose was cracked where the in-line filter was and replaced it. Thinking that would fix the problem but it didnt. I replaced the filter and the washers in it but guess i got it cross threaded or just not tight enough but never thought to put 2 and 2 together. I noticed the filter would have air bubbles so I did by pass it and the bulb gets hard now. HOPE that is it. Crossing my fingers. And I appreciate your help. I was bypassing it when you wrote this i guess. LOL

 

[ob]

Re: Johnson slips/cavitates after 35 minutes

Lets hope that alleviated your problem.At least you'll know that the bulb should pump up good and firm before starting in the future.I'll keep my fingers crossed.Make sure your fuel tank is venting also when you test run.Don't know what type of tank you have but some have a thumb screw vent valve on the cap.Others use a vented cap.

 

[swade28]

Re: Johnson slips/cavitates after 35 minutes

It has 3 separate vented caps coming out the console. At least i guess they are vented. I pulled off the hoses from the tank and blew through them. Air went through fine so I guess I am good there. Will see saturday how things turn out. May try to run out one night before then. Sure am anxious to see.

 

[fishmstr]

Re: Johnson slips/cavitates after 35 minutes

I have a 1996 Johnson Oceanrunner that has been doing a very similar thing for over 2 years. It first happened during a 20 mile run in from offshore. The motor feels like it completely cuts off then back on instantly. It will do this in succession a few times then if I let off the throttle, it smooths out. Sometimes it quits completely but starts back up fairly easily. It has done this some at lower rpms as well. I have made complete trips without anything happening. I've had a new stator installed, carbs cleaned, lower unit gears replaced, new spark plugs and a new gasline pump bulb. My mechanic wants to ride in it to be feel the symptoms for himself but it's too hard to coordinate getting on the water when it's convenient for both of us. There isn't much left to replace and he says it's probably the computer, which I guess are fairly expensive. Another mechanic I talked to today said he's seen this in OMC engines frequently and says it's likely the computer. He says they develop moisture for some reasons, which is why this problem is intermittent. What do you guys think?

 

[angus63]

Re: Johnson slips/cavitates after 35 minutes

Computer??? 1996 carbed motors have no such beast. I think they are referring to powerpack. Manual has procedure for checking that. They run in the neighborhood of $350. Your symptoms could be electronic or fuel related. I would check out fuel delivery first (pickup,vent,antisiphon,bulb, airleaks,pump diaphram,carb floats, etc...) and then do the electronic tests on all of the ignition components. Also could be going in and out of slow mode safety feature. Also could be intermittent short in cut-off circuit. Next time it happens, bump the primer and pump the fuel bulb to see if it picks up and you can go from there. Good luck and welcome aboard.<br />Also you may want to start a new thread for better response and a more accurate subject line.

 

[fishmstr]

Re: Johnson slips/cavitates after 35 minutes

Thanks for the ideas angus63.

 

[swade28]

Re: Johnson slips/cavitates after 35 minutes

I think mine was the in line air filter. It was allowing air to get in. I ran it couple weekends ago and could not duplicate problem. Fingers crossed for now. Scotty