Topic: Minor trouble with Johnson OB - "no oil" light.

[W9GFO]

There is probably a forum better suited for this question but I though I would ask here first since there is a lot of boat guys here.

I have a 1998 35hp Johnson. Every time (about nine days now) I take it out the "No Oil" light stays on (yes it is full of oil) for about the first 20 minutes and the motor will not move the boat faster than about 8mph before it sounds like the ignition is cutting out. I think the computer is limiting the rpm due to the light. After a while, the light goes out and it runs like a top. It'll push my 16' Lowe at 26mph fully loaded with four people aboard. Not bad for 35hp I think. If the engine hasn't run for an hour or so then there is a 50/50 chance that it will do it again.

A couple of times I have been able to make the light go out by smacking the oil tank. That trick worked only about two times and then only for a couple minutes. I have checked many times for loose wiring. I have jiggled and tugged every wire on that engine multiple times without any indication of a bad connection.

Any ideas what the problem could be?

[babarosa]

Not sure but you may have air bubbles in the oil line. If this engine self winterizes it self i would run that cycle a couple times. good luck.

[sonar2000]

I think there is a sensor for that and it may be going bad. I remember something like that on my Johnson a few years back..chuck

[W9GFO]

I decided to download the service manual. I found that the engine has a "S.L.O.W warning system" feature that reduces the engine RPM if it either overheats or senses that it is out of oil.

The oil level sending unit appears to be a small float that slides on a tube. One of it's three pins should show a low reading only if the float is at the bottom -  the one that triggers the warning system.  What doesn't make sense is that the issue goes away after running for a while. The only thing I can come up with is that the float is not as "floaty" as it should be and settles to the bottom. With the engine vibrating for a while it works it's way off the bottom. Not sure that makes sense either... I'll know more after I take it apart.

[bobcoy]

I am sure you are on the right track. If you have motor problems or almost anything to do with boats, I use Walleye Central .com. I hope I am not breaking the rules but It is an excellent resource. Just register and search the subject you want, or just ask your question on the appropriate board. Bob Coy