---

I have a '95 Montauk with a '95 Johnson OceanRunner 90HP. This boat is new to me (about 1 month) and I am the second owner. The boat and motor are both in like new condition. The previous owner seldom used the boat and it was garage kept. I am experiencing an odd problem with the motor that I believe was caused by the motor's lack of use and possibly dirty carbs.

When I run the motor at WOT I reach a maximum of ~5000 RPM and can cruise at ~43 MPH (Clocked on the GPS). However, on occasion the boat motor will drop approx. 1000 RPM to a WOT of 4000 RPM. At 4000 RPM the boat will cruise at approx 33 MPH (on GPS). It will run like this for an unpredictable amount of time (2 minutes to 30 minutes) then it will wake up, out of nowhere, and run at 5000 WOT again. Under normal conditions, when I can reach 5000 RPM WOT, I normally back off to 4500 RPM as my normal cruise speed.

Since purchasing this boat about a month ago I have ran about 80 Gallons of gas through the motor. Of that, about 32 gallons were treated with STP Concentrated Carbeurator cleaner. The tank of fuel I have in it now was also treated with Card cleaner. I have also cleaned the fuel filter and replaced the Champion spark plugs with Champion spark plugs.

Any further insight into what could cause this intermittent problem? It is annoying more than anything.

Thanks in advance.

---

dakqc,

I would be more inclined to look at your ignition coils. It seems to me that one or more of these coils are going bad. It could also be a power pack which would disable one side of the engine meaning you would loose 2 cylinders at a time.

I have a V6 that the power pack was doing the same thing only it would go slower than yours and then all of a sudden back to the speed I had the throttle set at.

---

I pulled the plugs and inspected then for normal firing. They look good. I also pulled the plug wires both at the spark plug and coil. I did not see anything abnormal. I am thinking I will buy a coil and swap it out with the upper one. If the problem presents itself again, I will take the old top one and replace the bottom coil pack with it. This problem is rather hard to troubleshoot because it is intermittent. I went through 50+ gallons of fuel between the time it last acted up and the most recent time. Very odd.

Thanks for your input.

---

I agree with you, this can be a hard problem to find.
I spent several days taking my boat out with a separate 6 gallon tank full of pre-mixed fuel and was experiencing the same problem I had.
The spark plugs won't show much if it is intermittent.
Because mine was so drastic, I was inclined to think it was the power pack which would shut off 3 of my cylinders. As much as I hate to buy parts just to see if that is the problem, I went ahead and bought 2 new power packs at $110 each.... Ouch....
But, that was the end of my problems and the power packs came with a 3 year warranty.
Not saying you need to do this, but an extra coil would not break anyone's pocket book that owns a boat.... If it isn't a coil, then you would have a spare for somewhere down the road.

---

Joe,

Where did you purchase the powerpacks? Your mechanic or an online resource? Just in case I get to the point where I need to purchase a Coil or Powerpack. Obviously, I would like to purchase Original OMC parts at the best possible price.

Thanks...

---

The plot thickens... I swapped out one of the coil packs and put it in the water today. Upon getting out of the no wake zone I went to WOT. Same result, I only hit 4000 RPM. So I went back to the dock and put the old coil I removed in place of the other old coil (So I have a new bottom coil and swapped the top coil with the other old one). Back out to where I could open her up and...the same result. So, I accepted that today I would be running around 4000 RPM (32 MPH) to my favorite fishing hole and back.

Well after landing a few stripers and preparing to head back in I was surprised to see the condition worsten. After drifting around and trolling for a little while I went to WOT and to my surprise I couldn't get above 2000 RPM (we're talking 8 MPH). So, I popped the engine cowl and played the coild rotation game again. No luck!

I then decided to start making my way back to the marina at 8 MPH. To my surprise...after putting along for about 10 minutes, some power came back. I was able to hit 4000 RPM again. Not the 5000 RPM I am used to, but heck, it was better than chugging in at 8 MPH.

Since the position of the new coil made no difference, I am resigned to think the problem isn't a bad coil. Now, I am left wondering wether or not I should just take it to the shop or trying changing out the power pack. By the way, what is the normal cost of a power pack?

Regards.

---

I vote for dirty carbs.

---

The Power Packs vary in price for different engines.
My packs were around $100 each.
OMC gives a 1 year warranty but Sierra packs had a 3 year warranty.
My mechanic ordered the Sierra packs for that reason plus the Sierra packs were a little cheaper if I remember correctly.

---

Good Evening!

Does anyone know what function the Grey wire (I believe Pin C) on a 1995 VRO electronics module controls? As I was troubleshooting my lack of Max RPM problem I discovered that the 4 wire bundle attached to the VRO Pump had been pinched and the Grey wire almost completely severed. I haven't had a chance to water test the boat after splicing the wire back together, but I suspect it may have been the root to my problem. We'll see...

Regards.

---

The Grey wire in OMC/Bombardier is usually the Tachometer Pulse signal....

---

I just wanted to follow-up and let everyone who is following this thread know the status of my rough idle and lack of horsepower problem.

After reading through various threads on a couple of discussion forums I came across one that discussed the use of a product called "Sea Foam" to clean the carburetors and decarb the motor. Well, I went ahead and bought some Sea Foam at my local advance auto parts. I bought both the can (liquid) and "Deep Creep" the aerosol.

To clean the carb's I started the motor and blasted the Deep Creep directly into the throttle bodies. If I had a schrader valve adapter I could have sprayed it through the choke solenoid. Anyway, I sprayed into all for air inlets with the motor at 1000 RPM until I flooded / stalled the motor. I then pulled the plugs and sprayed deep creek into the cylinders. I let this soak for approx 20 minutes. While the soaking, I went ahead and poured a pint of the liquid "Sea Foam" into my fuel tank to further clean/lubricate the ignition and fuel system while I run the boat.

After 20 minutes I cranked the motor over a couple of time to blow the excess deep creep out of my cylinders. I then replaced the plugs and cranked her up. She really smoked for about 10 minutes. This was to be expected, according to the directions on the can.

I repeated this process a second time then rinsed. By rinsed, I mean I trailered her down to the water and did a water test. All I can say is... WOW!!! This stuff worked a miracle. The motor ran like new. I was hitting 5200 RPM at WOT and at idle she purred like a kitten. I figured I had better blow this motor out. So I took her for a 2 hour, round trip, ride down to my favorite creek/cove where there is a really nice restaurant on the water.

The whole trip we average 42 MPH (via GPS) at 5000 RPM. I must say that "Sea Foam" saved me a trip to the boat shop and allowed me to keep the boat on the water in the peak of the season. I highly recommend that anyone who feels their motor has lost some horsepower should at least give this product a try. Heck, at Advance Auto Parts the pint of the liquid Sea Foam was less than $6.00 and the Deep Creep was about $7.50.

Sorry for the long post.

Regards...

---

JJS - You won... Dirty Carbs. ;)