MERCURY 100 (1990)-running rough, no prop power

owlcritic · #1 February 9th, 2007, 01:09 PM

[u]History:[/u] My boat was out the water for a couple of months. I replaced the control cables as well as the oil pressure switch. Also overhauled the control boxes (quicksilver). The oil pressure alarm continually sounds as soon as the ignition is switched on.
Problem:
One engine, since then , is running rough and delivers no contribution to propulsion. I replaced all the plugs to ensure firing on all cylinders - after the prolonged inaction. Makes no difference however. The engine idles okay although it will emit a hiccough every now and then... Open throttle fails to produce the required revs.

Suggestions please.

tashasdaddy · #2 February 9th, 2007, 01:54 PM

have you check compression, spark with a spark tester. is the engine reving up and producing no power at the prop. have you check link n sinc?

owlcritic · #3 February 9th, 2007, 03:36 PM

First two about to do...

Please explain " check link in sink"

Thanks for your help!

tashasdaddy · #4 February 9th, 2007, 06:46 PM

link n sink, is the synchronization of the electronics, (Spark) and the carboration. Gas. it is a step by step process cover in the manual for your particular engine, Mercs are very touchy about this. in replacing the control cable you could have gotten if out of adjustment,

tashasdaddy · #5 February 9th, 2007, 06:50 PM

are you sure the plugs wire are in the right position.

owlcritic · #6 February 10th, 2007, 01:04 PM

Have now checked spark etc in accoordance with specs...
Found that there is no spark on cylinders 2 & 4 - Firing perfectly on Cyl 1 and intermittently on Cyl 3.
Coil resistance test according to specs.
No response on static advance when operated by hand.
Ohms spec on TRIGGER not in my manual tables - could it be a factor and what steps do you suggest to isolate the problem?
Help will be appreciated