1990 90HP nissan

I have a 90 Hp nissan outboard. The compression is 128, 122, 120. I have had the carbs cleaned, taken the CDI and coils off and replaced with a Gm ignition system. Three ign modules and three coils. It will start and idle fine and rev fine but when engaged in gear it will idle but wont respond to the throttle like it should. We have tried adjust the carbs on the lake checked the fuel pressure which is right around 5Lbs. Please Help!!!!

Re: 1990 90HP nissan

Assuming you have an NS90A. Difficult to say for sure, especially with your modified ignition system, but I can think of 2 possible areas to check:

1- It sounds as though you may slightly too lean, especially if you are getting a "bogging" or air sucking sound -- especially only under load. That is a frequent symptom of a motor that runs/revs fine on muffs, but cannot deliver power under load... if the carbs are a little lean due to some varnishing. (What method was used to clean the carbs?)

2- Keep in mind that the original CD had the spark advance figured in, adjusting for the briefer trigger pulses of higher RPMs, by extending (stretching) the spark pulses, along with the advance from the throttle link. Your new modules may or may not have that kind of circuitry built-in.

I would check plug color to see if there are any clues that point to a lean condition, and I would verify link and sync, as well as checking timing with a traditional timing light. If you can lay your hands on an old Merc-o-Tronic or similar ignition scope, you can dx the ignition system to rule it out.

Re: 1990 90HP nissan

Paul,
Thank you very much for the quick response. We used Berrymans B-12 Carb cleaner and just took the carbs a part and sprayed all the jets and ports then blew them back out with 100 lbs of air pressure. I can tell you it is running a little lean. I have wondered about the timing advance myself. I bought this boat and motor three months ago and took it straight to the shop. They promised this was a much cheaper fix than replacing CDI, coils, and stator, stating there was a break down some where and it was pretty much just a trial and error method of fixing and if i got a part and tried it, it was mine.

Re: 1990 90HP nissan

You need a better mechanic. Your shop clearly does not understand how that ignition system works.

Proper carb cleaning would require complete carb disassembly (including jets and emulsion tube nozzle), a 4-hour bath for all bits in real carb dip such at Tyme, then a thorough blow-out with carb spray, followed by a careful reassembly, paying particular attention to float height. Carb spray in and of itself is not aggressive enough to dissolve most of the organic deposits left by the evaporation of today's poor fuels.

That motor does not have a stator; One exciter coil (only available for serial numbers 20995 and up), three pulser (trigger) coils (only available as a complete pulser plate assembly), the CD, and 3 ignition coils. Most expensive piece is the 3B7061602M C.D. IGNITION UNIT (F8T20571/8508) ($354.78 at retail). All parts of the ignition system can be tested with a good, conventional ANALOG ohmmeter, which must be 3v or less, to avoid blowing any of the internal circuitry in the CD. A good wrench will use the Factory service manual as a guide, and test the ignition components against the matrix in the manual to Dx whatever faulty part there may be. Wholesale parts swapping -- the "shotgun approach" -- while usually effective, is the most expensive way to repair an outboard.

At this point, I would definitely go through the carbs. Properly. The Chevrolet ignition may be fine as it is, so Dx one system at a time, until you discover the malfunction.