loss of power 1981 75 hp mercury ob

[mercrude]

1981 mercury 75 hp ob <br />I was cruising across the lake and all of the sudden I lost some power more than half the boat used to go about 40 mph now it will go about 15 to 20 mph could this be a power pack failer? and if so how do I check this ? any suggestions?

 

[ob]

Re: loss of power 1981 75 hp mercury ob

mercrude, The first thing I would do is perform a spark test to see if you in fact dropped a cylinder.Any further dignosis from my view would just be speculative.Post back with results.If your not clear how to do it you can do a search on these forums . Lots of good info.

 

[tmcalavy]

Re: loss of power 1981 75 hp mercury ob

Buy a spark tester that lets you test spark one wire at a time, while the wire is on the plug. Don't pull the plug and try to ground it to the block to test spark on your Merc. You can burn out the power pack this way, or so I have read on this very forum. A while back someone posted on how to make a spark tester, but no one answered my query whether it is safe to use on electronic ignition Mercs. Another post mentioned spark plug boots that light up as the spark goes through them. I need to do this myself, to test a sluggish Merc 500 50 hp engine from the mid-70's. Can someone advise on how to safely test spark on these Mercs?

 

[mercrude]

Re: loss of power 1981 75 hp mercury ob

I have not had a chance to test for spark nor do I know how but I did pull #1 plug wire while Idling and had no change in performence