Setting timing on Johnson 90 Jetdrive

**PhilN** · 09-08-2018, 12:19 PM

How is it possible to properly set/check the timing on an 89 Johnson 90 with a jetdrive? I have the factory manual and it mentions it must be done under load with a test propellor which isnt possible with a jet. My motor is missing some hp and it is hiccuping during idling. I did mess with the timing after rebuilding everything and know it isnt right. Adjusted it with the boat running on the trailer, not the right way. No one in my area will touch these old motors. Any help is appreciated.

**PhilN** · 09-11-2018, 11:48 PM

Anyone? The only times ive ever asked for help no one can help.

**ChampioNman** · 09-12-2018, 07:54 AM

We don't do a lot of jet motors. I've never worked on a motor with a jet drive on it.. Maybe Juggie or Seahorse has.

**316jughead** · 09-12-2018, 08:46 AM

I've never worked on one either.

**316jughead** · 09-12-2018, 09:29 PM

Question. Is this just a 90 HP outboard with a jet drive kit?

**PhilN** · 09-15-2018, 01:25 PM

It is just a plain johnson with a bolt on san leandro jet

**ChampioNman** · 09-16-2018, 07:03 AM

Leave it on the trailer and run it WFO check the timing.

**PhilN** · 10-14-2018, 07:46 PM

Thanks for the bulletin Jerry. I checked it at 3000 rpms and it was retarded quite a bit (like me). I had it set 5 degrees low while running it WFO on the trailer. Being a jetdrive, while on the trailer it can get up to an almost true under load max rpm. Im going to check the plugs and do a little more fine tuning but definitely solved my problem. Thanks guys!

**316jughead** · 10-15-2018, 12:59 PM

I tried to post the service bulletin here for all to see, but it wouldn't let me.

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Setting timing on Johnson 90 Jetdrive