99 Mercury Force rough idle, sputter at WOT and no Tach

[401scibz]

Hey everyone new to the forums. I have been lurking on here for quite some time trying to find topics related to my problems but after reading alot of mixed stuff i figured i would just hop on and see if anyone can give me a fresh set of diagnostics for these issues. I am pretty tech savvy and i know my way around a car well. Decent with electrical but no pro. This is 2nd outboard owned but the first one never gave me any issues.

Motor: 1999 Mercury Force 40hp serial # OE359169

Issue #1
No tach

So i have read that the Voltage rec and the stator are the typical causes of this issue. Myself and a friend read for quite some time on here how to test both but i have a feeling we went wrong somewhere along the line because our results were always varied. However we did jump from the voltage rec to the tach (on the apparent input signal for the tach from the voltage rec) and had a working signal. So im thinking the tach itself is working, But i could be very wrong. I am hoping someone could link me to a proper diagnostic page. or give me a breakdown on how to test both the stator as well as the voltage rec. NOTE: one of the yellow wires going from the stator to the voltage rec is burnt and the protective film around the male/female ends is melted and black. All other wires are OK

Issue #2
Rough Idle

When i first got the boat the idle was actually pretty good. It would die out the first few starts every now and then but once its warm it tends to stay running without sputtering out. Ever since i tried to diagnose the stator and voltage rec the idle went bonkers. I did read and adjust the fuel/air mixture knob on the carb to 1 1/4 turns out a few days later and it does idle better, but will still die out here and there. I do not have the OEM Champion plugs in the boat it has aftermarket NGK plugs in it that look nothing like any spark plug i have ever seen. Any info or things to check with this is much appreciated. I can post NGK PN# later tonight.

Issue #3
Sputter at WOT

Not always, but sometimes i will get sputters at WOT and it feels like the boat is not taching out, but running somewhere in the 3200-3500rpm range. I could be wrong again because i dont have a tach. The boat does about 27-28 mph and im pretty sure the prop is not OEM either. I have a feeling that one of the two issues stated above my be causing this issue. Any insight into this issue is appreciated as well!

Thanks for any help in advance!

 

[jerryjerry05]

First do a compression and spark test.
These 2 cyl. can run pretty good on 1 cyl.

Rough idle: could be a dirty low speed jet, or the reeds are bad, the recirc system dirty, low compression, water in the fuel,

Reg. test.
1. At 800-1000 RPM, check output on the gray wire, reading should be at least 8 volts with a DVA meter. A low reading usually indicates a bad regulator if the system is charging the battery. 2. Check the resistance between the gray wire and engine ground. You should read above 100K (100,000) ohms. Gray to red, and gray to the yellow wires should be a high reading, usually in the M range.

If this tests OK then the tach is probably bad.
​Get a timing light with a tach readout or a Tiny Tach .

The plugs are called surface gap plugs and have been around for YEARS!!!
​The parts diagrams call for Champion or the NGK equivalent
Champion L76V or QL76V
Both Champion or NGK work well.

Oh yea welcome.