Merc that misses and tach goes wild...

Hello,

Looking for suggestions on how to fix a problem with my 1977 AMF Crestliner Crusader that has a Merc 188 HP Ford 302 c.i. motor with a Rochester 2 barrel carb. All was working fine for the first couple of months this summer then all of a sudden the tach bounces and is way off from what the motor sounds like it is doing for rpm. Also, when I throttle it above a crawl is starts to cut out (sputter). I have replaced the fuel filter in the carb and tried disconecting the tach with no positive results. I tried running it with the gas cap removed and that did nothing. I get spark at all cylinders and am using new gas. Flame arrestor is clean and there is nothing obstructing the prop or impeller.

It feels like the carb is not getting enough gas. The accelerator pump looks like it is working fine. However when I throttle, after the initial spurt of gas, there appears to no steady supply of gas, just enough to make it sputter along and if I give more throttle it dies. It does this in forward, reverse and neutral but idles and starts just fine. I did no work on the boat before the problem started so I believe it is still timed correctly.

I think it might be the fuel pump but why is the tach acting to goofy?

Could there be a problem with the coil or distributor making the tach think the motor is running at a higher rpm than it is?

Any help would be greatly appreciated.

thanks
sonner711

Re: Merc that misses and tach goes wild...

Might have a look at the coil tower, if it's cracked or has carbon tracking on it it may be arching to the negative terminal of the coil. Your tach is hooked there, so you would have a miss, and a tach problem.
Many times the tower will crack because of a faulty plug wire or a plug not firing.

Re: Merc that misses and tach goes wild...

Check the condition of the points and the point gap.

No load,less electrical load, in gear and throttling in gear requires moree electrical load and the points arc and miss-fire, causing the engine to stagger and the tach to read erratic.

Also check the condition of the plug wires with an ohm meter.

Poor wires willl cause simular misfires and erratic tach.