1996 225STURU-Engine shutter at low RPMS

[zenoahphobic]

so is your suggestion to run it for an hour or so until the RPMS start dropping, then switch to the small tank?

I think just start and run it on seperate tank to see if problem happens and take from there.
Switching tanks on the fly difficult not to introduce air into a makeshift two tank supply

[jukes23]

Not against trying it, but these problems sound like something that would occur right in the beginning, not after the motor has been running for a while

[zenoahphobic]

Not against trying it, but these problems sound like something that would occur right in the beginning, not after the motor has been running for a while

Slight contradictions within your postings about the timeframes

[rodbolt17]

do you ever have a random cyl spark plug fouling??

there were some stator issues on the early 3.1L engines that as they heated up the charge coil voltage would diminish.
at about 65V the ign coils cannot step up the secondary voltage.

have you tested the alarm audible????

[jukes23]

Thanks for the insight Rodbolt. I have had random plug foulings, typically just one cylinder. How do I test the alarm audible? Would this also cause that shutter?

[bajakeith]

shutter

you might also try a high speed shut down (when acting up) and check plugs...

[jukes23]

I can try that.

This has been the most frustrating problem ever.

[jukes23]

I am wondering if there arent 2 problems going on:

1. The low RPM shutter: I've heard motor mounts to imbalanced prop to partially spun hub to prop shaft wobble. Not sure about the motor mounts (do outboards even have motor mounts since its all a motor ), but the prop item maybe something worth checking out. I borrowed a prop from a friend and when I take the prop off, I will check for prop wobble. Any idea about these motor mounts.

2. The RPM's dropping off after the motor warms up. Definitely a mystery and from what I have read so far, Rodbolt's suggestion around the stater is worth checking out.

Rodbolt, how do I test the audible alarm and check out the stater?

[rodbolt17]

a quick test of the audible? simply pull the E stop lanyard and crank it.
if it sounds your ****en if not find out why.

from there its monitoring the CDI output when its failing.

[jukes23]

ok, the audible alarm works fine.

How do I monitor the CDI? Would it be wise to take it to a mechanic who has the proper diagnostic tools to figure it out? The guy I normally use has a 2 week backlog...not a problem as I am getting ready to take a 2 week vacation!

[rodbolt17]

only way to test the CDI output WHEN the engine is failing, is hook up a peak reading multimeter and run it till it fails.
the ECU wont monitor charge coil voltage.

in a pinch for this, monitor AC volts on the ign coil primaries and see if it drops more than about 20V.

[jukes23]

Thanks Rodbolt. Are the ignition coil primaries also referred to Ignition coil assemblies? So when the problem starts (RPMs drop to 4800 RPMS), how do I test the ignition coil? Where do I attach the lead on the meter to? You said " see if it drops more than about 20V". Does that mean check each one and see if it drops below 20 v? Should it produce more than 20V always or only above certain RPMs

[rodbolt17]

ok
pissed off,half liqured up and you have no clue.
bear with me.

on each coil ther is a bullet connector.
that is the CDI output.
tap into that with the red lead.
ground the black lead.
aint even going into Peak reading meter tonight.
place the meter on the AC scale.
run it.
should not change more than about 20V from the time you start it till the time it fails.

what your looking for is did something change.

technically the CDI output is DC voltage.

however as it rises and falls so fast it almost looks like AC voltage.

most meters buffer it down to the 70% working voltage.

in a pinch monitor it from running good to bad, if it changes more than 20 V get the correct test equipment.

[jukes23]

LOL. I think I got you. Thanks for the help.

[jukes23]

One other question. I want to make sure I have the proper prop on this boat. When I bought it, it came with a SWS M17 prop. Is that the appropriate prop for it?