2002 Johnson 175 Carburated Optical......

[Trippin]

Been trying to resolve an engine "cut out" issue at high speed. At 5000-5300 rpm (WOT) the engine knocks out cylinders ( but not immediately, after running hard for a minute or two, or three). I assume this is the power reduction engaging, however I have no alarms. If I turn off the ignition and re-start it the engine operates just fine until I hit 5000 again. So not fuel either. Had a power Pack in stock and replaced it in the hopes but it did not resolve the issue.

Could it be the optical module? I don't have the tester. Or could it be something else electrical? Stator short?

Anyone else familiar with these engines?

[Lockjaw]

You sure your tach is right? Could it be bumping the rev limiter instead? Only thing that reduces RPMS is overheat alarm. At least on my 96. Low oil, no oil or fuel system vacuum just set off the alarm and light up a light in my tach.

I have never had an optical eye fail. The sad part is the part itself is probably cheaper than what a tech would charge to check it. Racer told me the stator going bad usually mainifests as a weak spark.

What kind of boat, set up, prop speed etc?

[Trippin]

You sure your tach is right? Could it be bumping the rev limiter instead? Only thing that reduces RPMS is overheat alarm. At least on my 96. Low oil, no oil or fuel system vacuum just set off the alarm and light up a light in my tach.

I have never had an optical eye fail. The sad part is the part itself is probably cheaper than what a tech would charge to check it. Racer told me the stator going bad usually mainifests as a weak spark.

What kind of boat, set up, prop speed etc?

1. Yes the tach is correct, I had my multimeter attached to the engine while underway just to make sure (that was my first inclination too, good call). Topped out at 5350. So not bumping the rev limiter. Guess I'll take off the optical sensor assembly, flywheel and stator and check for shorts.

2. 19' Stratos, 6" manual jack, 14.5 X 24 Michigan Wheel

Thanks for the reply nonetheless.

[1nebel0]

I have a testor for sale if interested......

[PanRonnie]

miss at any rpm
reason 3!

[Lockjaw]

You need a different prop, you should be turning 5700, that is where the 175 makes peak power. Once you figure out what your issue is.

Kind of tough for me to buy the coil wires since you replaced the pack, but I guess you could have gotten a bad pack.

[Trippin]

Still working on this thing.... Off and on. When I say that it drops cylinders I mean it has gone into slow mode. So churning along at 4800 rpm everything is fine, can do that all day long. Once I get up into 4900+ esp. 5000 it knocks me into slow mode. Sometimes immediately other times with a slight delay, but always, eventually. I have had an alternate tach connected and it also read 5000 +/- when it went into slow mode several tests. However as I mentioned above, no alarms, not overheating, I can turn the engine off then right back on and take off like nothing ever happened. Replaced the power pack now, no change. The only thing significantly different about this engine is that it came to me with different plug wires on it. After market, Magstar 8.5mm Super Inductive's.... I wonder if that could be causing an RFI issue or resistance issue....Seems unlikely.

PanRonnie thx for the troubleshooting manual...

[Trippin]

I'm gunning for the blocking diode now.

[Fairbanksrabbit]

Did you check to see if the timing wheel is loose? Is the power pack OMC or aftermarket?

[flabum1017]

Try disconnecting the temp alarm sensor and fuel restriction sensor and see if the problem goes away..... could be a partial short throwing it into safe mode

[pauldavid]

its either fuel restriction or water flow and since its not burnt down by now i lean more toward water flow, how high is your motor setting could be suckin air at higher rpms either lower the motor a tad or plug a couple of the top intake hole where it pulls in water and see what happens. could even be a weak water pump

[Action Mike]

I have a Johnson 150 looper running a 22pitch prop it won't go over 4200 on a 19ft action can it be prop issue or what do you think ? Need help lol all cylinders are working with 98 of compression

[flabum1017]

I have a Johnson 150 looper running a 22pitch prop it won't go over 4200 on a 19ft action can it be prop issue or what do you think ? Need help lol all cylinders are working with 98 of compression

Try starting your own thread

[NH LTV]

I had one that was skipping at around the same RPM range. When I shut it down and restarted, it was fine. The problem was mice had chewed up some of the foam from the cowl. The little pieces of foam worked their way into the flywheel cover. At high RPM, they were floating around and interrupting the Optical sensor signal. The fix was a shop vac.

[iwantaVirage]

ive had the fuel restriction/vaccuum sensor go bad on several motors through the years, id def try disconnecting that to see. ive also had optical eyes go bad(even had a bad one right out of the box one time)-- the other common part i remember replacing was the regulator/rectifier and on occasion the stator-- i also remember not being able to get the idle timing correct or get full advance out of one motor and although its been a while, i think the trigger magnets came loose or something to that effect-- but its been a few yrs so not 100% sure on what the cause was for the timing thing....
hopefully the little bit of info i can remember on that motor helps in some way!