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I finally got the charging issue with my 1987 Johnson 90 fixed with a new voltage regulator, which fixed up some of my tachometer issues. I took the boat out for another trial run with a working tach to get some performance numbers. After about 10 miles running up and down the river, I suddenly lost power. I could not get over 2000 RPM.

I nursed it back to pretty close to the launch ramp, then decided to shut down and see what would happen when I restarted. Would only start when I had it "revved up." I could not drop back into gear before it killed. It would not start sitting in neutral. It turned over fine.

I will be calling the mechanic AGAIN. Any ideas?

The top engine speed was only 4300 RPM. I will check the prop numbers later but it seemed to run pretty well when it was running as it should. I had more of a feeling that the tach was wrong rather than the motor was over propped severely but I have been wrong before.

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And the VRO is disconnected so essentially it Does NOT Have VRO....

You mix your own oil into the fuel?

An engine will still run even if the battery is dead.
Do you hav a voltmeter onboard that tells you your charging system is working?

I don't believe the 1987 models have S.L.O.W mode but maybe yours is overheating...
Is your tell tale water stream strong?

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yes VRO is disconnected - i mix my own fuel exactly. the motor water intake system seems to be working very well - pleanty of strong stream output and i felt it - very cool. motor doesn;t seem to running hot.

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Check the vent in the gas tank and check if it runs better while you pump the primer bulb.

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fuel tank and line is fine - it ran 10 miles then suddenly had a problem.

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The advice to pump the fuel bulb is to check whether you have a weak fuel pump. The tank vent is simple to check too.

Do you have the tech manual for that motor? I am not sure, but I think the 87s had the S.L.O.W. system that limits the motor to 2000 RPM in certain failure conditions, such as overheating. If you were really turning only 4300 RPM at full throttle, and ran for an extended distance like that, you may well have overheated. If so, the warning buzzer should have gone off too - that's assuming you have a warning buzzer, and it's working.

Tim

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I've replaced a few fuel pumps on similiar late 80's Johnsons and Evinrudes recently that were kind of doing the same thing as you've described. The pumps aren't difficult at all to get to or replace.

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don;t have a tech manual and ... i'm not a mechanic. i will ask the mechanic to check my warning buzzer ... as i mentioned earlier - it ran "fine" for 30-40 minutes on a plane at an average of around 28 knots or so until this problem occurred. it's at the shop now again. mechanic thinks either carbs or ignition system ... to him, it shut down 2 cylinders.

thanks for the suggestions. will keep updated as things occur. maybe anyone else with my motor will get some additional insight.

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A defective Power Pack can operate normally until it gets warm and something inside of it expands just enough to interrupt the electrical current and then shut down two of the four cylinders.

Cooling of the Power Pack can return it to normal operation thus making the problem difficult to diagnose.

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winner winner chicken dinner ... bad power pack. as a side note, i am going to have the carbs rebuilt too so that all my potentials are reconditioned. thanks for all the info.

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okay - replaced powerpack 1 - ran 10 minutes, maybe at cruise to WOT and babboom, dead powerpack again. can powerpack 2 short out power pack 1 ??

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Have you verified that the ground connections are perfect?
Zap

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i'm not the mechanic - i use a guy with 25 years experience who is kind of the expert in this series motors. i will check with him ...

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I believe power packs are common with that paticular motor. My brother had the same problem and finally re-powered with a Merc.

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the problem is solved - it turns out powerpack 1 was shorting out power pack 2. with both power packs replaced i can tell a big difference in the way the motor runs - and carb rebuild ...

thanks for all the comments.

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I'm confused... There is only 1 power pack on a 1987 90hp Johnson.
What part did you change ?

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According to the BRP Online Parts Catalog there a two (2) power packs for the 90 hp motors. One for each head or bank of cylinders.

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Sorry my bad. They switched over to the single pack in 1988 not 1987

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Note to the OP:

Make it a point to check your major electrical connections frequently to make sure everything is snug, secure and clean. The powerpacks on these engines are notoriously fragile, and even something as minor as a slightly loose battery connection can fry them.
Tightening a couple of nuts and bolts every few weeks doesn't require a lot of technical acumen, and it could spare you some trouble down the line.