1984 75 hp. Mercury Outboard - not kicking in other two cylinders

[Wistickbowman]

I've been trouble shooting my 1984 Merc for the last week and a half. It will start fine and idle fine. At home w/the muffs on, it will also reve fine. When I put it in the water and run it on the boat, it will idle along at slow rpms. When I punch it, the other two cylinders will kick in for a second then out, then in, etc. Kind of like it's shorting and the cylinders are kicking in and out (too quickly in my mind to be any kind of a fuel issue).

First things first, I took it in and had the compression checked - all was okay.

2nd - replaced all fuel lines and bulb to rule that out - no better

3rd - replaced spark plugs - no better

4th - plug wires - same deal

5th - had mechanic test stator - said fine (will come back to this)

6th - replaced switch box (power pack) - no better

7th - bought a 2001 90 hp and mounted that - BETTER!!!!

Now I still want to get this thing going so I can sell the boat I robbed the other motor off of after I get my old motor running on it.

The mechanic at the marina I got the new boat/motor from suggested that the high speed coils in the stator are shot. Another suggested the trigger. Any thoughts before I shuck out another couple hundred bucks on a new stator and another $150 on a trigger???

I called the mechanic back who had tested the stator and asked if he had just checked the low speed stator, and he said yes, and that the only way to check the high speed stator was while on the water.

 

[Wistickbowman]

Re: 1984 75 hp. Mercury Outboard - not kicking in other two cylinders

Bueller????? Anyone??????

 

[Wistickbowman]

Re: 1984 75 hp. Mercury Outboard - not kicking in other two cylinders

As an update, I got my hands on a Clymer Service Manual and ran through the diagnostic tests for the trigger and stator, checking resistance and continuity.

Trigger checked out fine. One of the readings on the stator was supposed to be in a range of 56-72 ohms and came back at 140 ohms. Can't find any place where there's a short, so ordered a new stator. Will post if that does the trick.

 

[Wistickbowman]

Re: 1984 75 hp. Mercury Outboard - not kicking in other two cylinders

Wasn't Stator either. Taking to a retired Merc Engineer on Friday. Will see what he comes up with.

 

[CDI Tech Support]

Re: 1984 75 hp. Mercury Outboard - not kicking in other two cylinders

I've been trouble shooting my 1984 Merc for the last week and a half. It will start fine and idle fine. At home w/the muffs on, it will also reve fine. When I put it in the water and run it on the boat, it will idle along at slow rpms. When I punch it, the other two cylinders will kick in for a second then out, then in, etc. Kind of like it's shorting and the cylinders are kicking in and out (too quickly in my mind to be any kind of a fuel issue).

First things first, I took it in and had the compression checked - all was okay.

2nd - replaced all fuel lines and bulb to rule that out - no better

3rd - replaced spark plugs - no better

4th - plug wires - same deal

5th - had mechanic test stator - said fine (will come back to this)

6th - replaced switch box (power pack) - no better

7th - bought a 2001 90 hp and mounted that - BETTER!!!!

Now I still want to get this thing going so I can sell the boat I robbed the other motor off of after I get my old motor running on it.

The mechanic at the marina I got the new boat/motor from suggested that the high speed coils in the stator are shot. Another suggested the trigger. Any thoughts before I shuck out another couple hundred bucks on a new stator and another $150 on a trigger???

I called the mechanic back who had tested the stator and asked if he had just checked the low speed stator, and he said yes, and that the only way to check the high speed stator was while on the water.

After you've exhausted all mechanical issues:

CDI Troubleshooting Guide

Shortcut:

Mercury 4 Cylinder

Check the trigger DVA under "NO SPARK OR INTERMITTENT SPARK ON ONE OR MORE CYLINDERS:"

Keep in mind resistance is a highly unreliable check.

 

[jimmbo]

Re: 1984 75 hp. Mercury Outboard - not kicking in other two cylinders

Check see if any of the wires/connections short out/pinch as the stator plate moves as the throttle is advanced. an broken wire inside the insulation can create all sorts of intermittent problems

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Don S ‎(Moderator)
May 26th, 2011