Tuning a 1974 Merc 75 7.5HP

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Bracing248

Recruit
Joined
Jun 15, 2010
Messages
4
Can anyone advise me as to how to tune my 7.5HP, has been running great at idle, in reverse, and at WOT. Just the other day it has no WOT and almost need to feather the throttle to get any RPM's out of it, and at best get about 1/4th the normal. I've put in new plugs and a new gas line. At the beginning of the year had a similar problem but after a few sputters she ran like a champ, the sputter was as if it was only running on 1 cylinder. Any ideas, and how do you tune a carb for WOT with only 1 jet screw?
 
Wingedwheel

Wingedwheel

Lieutenant Junior Grade
Joined
Jun 16, 2009
Messages
1,071
Re: Tuning a 1974 Merc 75 7.5HP

first thing I'd do is pull the plugs and see if they're wet or show indication of firing. I worked on a 7.5 that had the same type of problems and it had a failed coil. When I pulled the plugs I noticed one was shiny and new and the other was a nice grey color. If your not sure clean the electrodes and try and run it. If there is a difference when you pull them back out it will be an indicator. A motor needs fuel and spark to run properly so you need to figure out if you have both. Simple tests can keep you from replacing things that don't need replacing.
 
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