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1987 Nissan NS55B Loses RPM on full throtle

B

Broby4206

New member
This engine stars and idles fine when cold. When I put it in the water it idles a little rough but when you throttle up it comes up on plane for a minute or so then loads up and eventually dies. It will at first restart but the problem gets rapidly worse until it won't even start. Seems to be flooding out. If you pump the primer bulb it gets worse instead of better. One mechanic said it could be the ignition module going bad. Can you send me the ignition test procedure or give me other recommendations.


This boat set for twelve years. All the fuel lines had to be replaced. The only rubber line that has not been replaced is the vacuum advance. It planes out fine at first so I wouldn't think it was the vacuum advance.​
 
There is no vacuum advance on a 55B.
I may have a reprint of the Factory service manual.
Many parts are NLA.
Send me a PM and I may be able to help you.
 
Last edited:
pvanv said:
There is no vacuum advance on a 55B.
I may have a reprint of the Factory service manual.
Many parts are NLA.
Send me a PM and I may be able to help you.
Click to expand...

What's a PM? The serial number is 353-1 12855.

What is the small hose on the starboard side of the engine that runs from the base of the engine where it attaches to the lower unit, wraps behind the throtle linkage and connects under the flywheel near the front? That's the only hose that hasn't been replaced.

I ordered a service manual direct from Tohatsu. It should be here in a few days. If it turns ouyt to be the ignition module it costs $265.

I was thinking about this some more and wondering if one of the two carbs is not getting enough fuel through the float bowl. When it's stumbling and I squese the primer bulb it makes it worse but could be drowning out the good carb/cylinder.
 
Tohatsu America does not sell to consumers.
The 55B is so old that it is not covered in the combined 1- and 2-cylinder Factory service manual.
I do have a reprint of the 55B and 70A manual.
You may be describing a lubrication recirculation tube.
The ignition system has a trigger coil, and exciter coil (both under the flywheel, near the alternator coil) as well as the CD box. again, many parts are NLA from Tohatsu, but may be available in the aftermarket.
You need to test all those components to verify ignitiion.
Did you disassemble and clean the carbs properly, and verify condition of the needles, and the float height?

PM is Private Message.
 
pvanv said:
Tohatsu America does not sell to consumers.
The 55B is so old that it is not covered in the combined 1- and 2-cylinder Factory service manual.
I do have a reprint of the 55B and 70A manual.
You may be describing a lubrication recirculation tube.
The ignition system has a trigger coil, and exciter coil (both under the flywheel, near the alternator coil) as well as the CD box. again, many parts are NLA from Tohatsu, but may be available in the aftermarket.
You need to test all those components to verify ignitiion.
Did you disassemble and clean the carbs properly, and verify condition of the needles, and the float height?

PM is Private Message.
Click to expand...

Actually I ordered the service manual from Nissanautboardparts.com but it shipped from Cumberland Watersports. I did dissamble and clean both carbs but believe I'll do it again and then blow smoke through all the passages to be sure they're all clear and check the float height.
 
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