Cannot get motor past 3300 rpm.

[slamoflange]

I have a 88' 45hp Classic. Cylinder 3 gets no spark. Have had in shop 3 times and am getting a little pi**ed. They have replaced coil, plugs, wires and high speed stator. last time they said it was repaired we took out yesterday and same problem. Any ideas would be nice so I have ammo to take with me when I go back? Thanks, Bob

 

[verado7]

Re: Cannot get motor past 3300 rpm.

my thoughts are that you have a bad switchbox - they should have done a complete test of the ignition - if you have a regular multimeter you can put the positive at the switchbox terminal that leads to the coil and cyl. with no spark -and ground the other lead to the block or a starter bolt - since you have no spark you shouldn't get anything on the meter if you see some movement take it back and have them test it with a dva meter -again they should have done this .

 

[Faztbullet]

Re: Cannot get motor past 3300 rpm.

Could be a bad trigger, bad switchbox or bad rectifier. Here is internal diode test for switchbox.

 

[backyard mechanic]

Re: Cannot get motor past 3300 rpm.

Check the compression before you go any further. Meanwhile; if # 3 isn't firing and you've replaced wires, coils and plugs. If it's a Merc it's gonna be an electrical component like the trigger. Usually the switch box works or it doesn't. The trigger sends an impulse from the stator to the switch box to the coil to the plug. There is a dva test meter that can be hooked up to your quality multimeter. The hook up and reading values are in the manual.

Be sure all the other stiff is right before you spend a lot of money on a switch/component part only to find a blown engine.

 

[EazzeO]

Re: Cannot get motor past 3300 rpm.

Hi
I had a 20 hp merc with the same problem. It was the trigger that was faulty. It can be check by testing
The resistance between both wires (ohms). it sounds like they did not test anything and just throw
new parts at it I would suggest going somewhere else.
Well good luck with it.
Cheers

 

[verado7]

Re: Cannot get motor past 3300 rpm.

switchboxes can work or not but thats not written in stone - you can lose 1 or 2 cyl. depending 3cyl or 4 - ive diagnosed a many like that -and 1 time on my 4cyl. when i lost the bottom 2 cylinders - new switchbox away i go .