1985 Johnson 90 dies suddenly at low speed and restarts after much cranking !?!?

[baltra]

I rebuilt this engine about a year ago and it ran fine just after rebuilt. Last weekend on the water, it just died while running at low speed and about 1500-2000 rpm. I squeezed ball, pushed choke, pushed throttle and nothing worked. Tilted up and started right away, but died when tried to put on gear. Restarted after several tries, revved up in neutral, then Ran fine to dive site.
Restarted at once to go back home but died when trying to put in gear, twice. To restart, choke, ball, tilt, throttle did not work, it just restarted after several tries. Ran fine going home, idled fine approaching dock but wanted to die once docked. The sudden death without hiccup or sputtering may be the clue? And restarting just "because" may be signs of an electrical problem?

 

[emdsapmgr]

Re: 1985 Johnson 90 dies suddenly at low speed and restarts after much cranking !?!?

Do you know if the warning horn works? Possible you are having an overheat problem at idle. If either of the two thermostats stick shut, it will overheat at idle. Once a piston heats up, it can expand in the cyl and could quit running. (overheat lockup.) Once the engine cools and you get the boat up on plane, the pressure relief (bypass) valves in the thermostat housing will open, flooding the block with extra cooling water. Perhaps why it ran ok to the dive site and back again.

 

[baltra]

Re: 1985 Johnson 90 dies suddenly at low speed and restarts after much cranking !?!?

I do not know if the horn works, but i've never heard it, I will check that! However, I suspect overheat lockup not to be the problem as it restarts within a minute or so after it dies. The water pump, components and thermostat were replaced during rebuilding, so I assume they're working ok, I've checked temp of all cylinders on the muffs and it's ok? Around 140f, but you bring up a very good point about the horn, thanks!

 

[emdsapmgr]

Re: 1985 Johnson 90 dies suddenly at low speed and restarts after much cranking !?!?

If you've replaced the stats and impeller, it could be an ignition problem. When the engine starts to act up, check each spark plug wire for spark. An inductive timing light comes in handy for this test. The flashes from the gun will tell you a lot about the quality of spark on each wire.

 

[pn]

Re: 1985 Johnson 90 dies suddenly at low speed and restarts after much cranking !?!?

i'm guessing to take a closer look at your remote control, and the electrical kill wire stuff. there's a couple of circuits that keep you engine alive, look at that stuff carefully, inch by inch.