150 johnson shutters

**CharlieB** · 07-20-2004, 09:19 AM

I need help here guys. wierd problem. Running down the lake the motor just loses power big time drops off plane to nothing and shutters violently. If I rev it gets really bad. Almost looks like It's losing a whole bank. Shut the key off and restart she purrs like a kitten and won't do it for the rest of the day. This happens at least once a day every time out. 150 Johnson 2002 carb....... could it be the power pac. They usually go completely when they go I thought..

**captcarb** · 07-20-2004, 09:46 AM

It was the power pack. Repalce the water pump also if a new power pack and sensor fixes it.

Jim

**Raceman** · 07-20-2004, 10:19 AM

I think it's a textbook case of Mercfear. I had a neighbor once who's Evinrod would shut down every time there was a Merc comin'. Whenever the Merc would get on by, the 'rude would run as normal again.

**CharlieB** · 07-20-2004, 10:35 AM

Ya know it did always do it when I was follerin him Hmmmmmmmmm

**Waterdigger** · 07-20-2004, 01:04 PM

dat shuddering caused from constipation...... da eagle dun
eat a nudder Merk!

**Bill Rogers** · 07-20-2004, 01:54 PM

Charlie, sounds like it's going into SLOW mode. I think that stands for Speed Limiting Overheat Warning ... somthin' like that, anyway. It's probably just gettin' too hot. Pack senses the overheat and misfires on purpose to keep the revs down

**Scream And Fly** · 07-20-2004, 02:44 PM

Bill is correct - that is OMC's S.L.O.W. (Speed Limiting Overheat Warning) overheat protection system doing its job. I suppose if the engine is not overheating, the system itself can be malfunctioning.

Greg

**captcarb** · 07-20-2004, 04:26 PM

It will soumd a warning horn and be limited to 2500 rpm. It will not correct itself and be fine for the rest of the day like he said. I believe on a 96 and later there is a indicator that says what the problem is also.

Jim

**ON THE HUNT** · 07-20-2004, 06:15 PM

Check the shift switch, all those bushings and levers and shafts are known to bind up. So many engineers and so little zerk fittings...

**half fast** · 07-20-2004, 08:42 PM

Hey Charlie ,Those 60 degree loopers have a small pocket that the water must pass thru to get to the temp sensor.It may be clogged or even have some deposits left behind.The local OMC dealer told me he has had to remove the head and clean with an acid to clean the water passages in the head.FYI we are in fresh water too. hf...

**captcarb** · 07-21-2004, 09:34 AM

If it is the power pack like I think it is, it will get worse over time and with heat cycles. It took me a long time to be convinced that the power pack was my problem because it acted like a fuel poblem.

I let the water pump go too long in mine and although it had good water pressure it started running about 10-20 degress warmer than before (in the midrange) and I think the extra temp got the power pack. It never got hot enough to set off the alarm. The impeller still looked beautiful when I took it out.

Jim

**CharlieB** · 08-20-2004, 08:04 AM

Welp guys The brass ring goes to Bill Rogers Thanks .. It turns out that the impellor was original to this motor and around 4 years old. I guess by turning it off and back on it reset the S.L.O.W. circuit or something like that. I put a new water pump asm. in it Housing gaskets impeller and all seals. Flushed his system He has 15 hours on it since and not once has it happened. It was doing it on a regular basis al least enough to know it's gone now. Just thought yuze gize would like an update in case this problem pops up for ya.

Thanks again for all the ideas