1995 - 40hp Force has a 100 rpm flutter or miss

crkdltr

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Joined
Mar 2, 2011
Messages
5
It's kind of hard to explain the problem but I'll give as much information and detail that I can.

The motor is a 1995 Force 40hp mated to a 15" Cajun Special jon boat. The motor runs fine on cups and idles fine. The motor was sitting up for 2 or 3 years unused so I have gone through the whole motor. Compression on both cylinders were equal, I want to say it was 125 or 145psi, I can't remember which at this time. I've replaced fuel tank (new plastic tank), fuel lines, primer bulb, fuel filter, rebuilt the carb, rebuilt the fuel pump, replaced the spark plugs and the spark plug wires. I brought it to a mechanic to have him reset the timing/linkages after I tried to tweak them and screwed it up.

Since having it back it runs great, however, when I'm on plane and running I can hear in the motor and see on the tach that it's dropping 100 rpms intermittently. It occurs between 3k rpms and 5k rpms. The mechanic can't reproduce the problem when it's in the test tank because there's no load on the motor and when I accelerate from an idle there is no miss until after I'm on plane.

I'm at a loss for what can be causing the issue. In last speaking with the mechanic he thought the issue was ignition and had me switch from perma-gap plugs to traditional plugs. I did that and also discovered the plug wires were in poor shape so I replaced them as well. The only thing that hasn't been changed are the power packs, regulator/rectifier and the stator. I'm not even sure those would cause this issue. I thought about prop/hub slippage but it would seem that it would happen when I'm taking off and not when I'm on plane.

I'm just concerned if I keep running it this way something is going to happen.

Any suggestions would be greatly appreciated.
 

crkdltr

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Joined
Mar 2, 2011
Messages
5
Re: 1995 - 40hp Force has a 100 rpm flutter or miss

Did some further troubleshooting and think that my stator might be going bad.

According to my manual and CDI Electronics DVA (Peak Reading) Voltage and Resistance Chart my stator should have the following readings.

Low Speed (blue to blue white) 2200 - 2400 ohms or 3250 - 3650 ohms depending on ignition part number.
High Speed (red to red white) 28 - 32 ohms or 75 - 90 ohms depending on ignition part number

And then the trigger assembly

purple to white 800 - 1400 ohms.

My actual readings were:

Low Speed - 4000 ohms
High Speed - 105 ohms
Trigger - 900 ohms

So is it safe to conclude that the readings of my stator is outside of tolerance and could be the cause of my miss?
 

chasimo

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Joined
Jul 19, 2011
Messages
1
Re: 1995 - 40hp Force has a 100 rpm flutter or miss

I have a 40HP Force with identical problem. I have been advised that the engine might be carboned up. I decarbonized it yesterday eveing, but I haven't had a chance to take it out and try it yet.
 
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