motor wont start

kshra

Recruit
Joined
Jun 16, 2006
Messages
5
i have an 86 45hp mercury, when i first took the boat out it would only run about half speed and when it got hot and i turned it off it wouldn't start until it cooled off. i bought a new power pack and it would not run but about half speed. i messed with wires and the next time i took it out it ran great for about 1hr. when i turned it off and tried to start it wouldn't start. bought a new rectifier and still cannot start it. any ideas for me?
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: motor wont start

Simply throwing parts at the engine and "messing with wires" is not an effective way of troubleshooting. Do yourself a big favor and invest in a service manual for your engine. If that's not an option, try your local library as they often have them. The engine needs fuel, spark, air, and compression to run and everything needs to happen at the right time. First, a compression check is in order. If compression is ok check for spark on all cylinders. If that's not ok you need to troubleshoot the ignition system. Check the plugs to see if some are wet with fuel (too much fuel) or dry (not enough fuel). Check the cooling system (is there a good stream at the tell tale). If not, an impeller change is necessary. Is the engine overheating? If the alarm is not working you have no way of knowing but it sure sounds like you are running the engine hot. It then loses compression and an engine with little or no compression will not start. If you have spark, try squirting a little fuel/oil mix directly into the carbs while cranking. If the engine fires, you have a fuel delivery problem.
 

GA Paramedic

Petty Officer 2nd Class
Joined
May 30, 2006
Messages
103
Re: motor wont start

you just got yourself the best troubleshooting guide I have seen in a long time all rolled into a few lines. Methodical testing is the key. You'll spend more money doing it the other way and may not even find the problem.
 
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