80's 25hp Johnson lost power after battery terminals hooked backwards

walleyereaper

Recruit
Joined
Apr 29, 2013
Messages
3
Hi all I sent a boy to do a mans job, and now my fishing boat has lost performance. The terminals were hooked up backwards, on my 80's 25HP Johnson. I was told by my buddy as soon as the terminals were connected backwards there was a loud pop and white smoke billowed from the motor. I took the boat out to run it and make sure all was well, however it wasn't. The motor started right up no problem and idled fine, but when I went to open it up across the lake I only had half the horse power. On my way back to the dock one last time I cracked on it and a short burst of Full horsepower came, however it hasn't returned since. Could someone with more knowledge on motors please give me some input into this problem???? The walleye spawn is on and I need this boat to perform again!!

Thanks-Tom
 

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,129
Re: 80's 25hp Johnson lost power after battery terminals hooked backwards

Doing this often burns through some wires, they catch into flames. Inspect the insulation wires for burn marks and rejoin where necessary.
It will often burns up the rectifier so test that too.

you will be able to find the test for that by searching on this site
 

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,129
Re: 80's 25hp Johnson lost power after battery terminals hooked backwards

check you are getting spark on all cylinders too
 

walleyereaper

Recruit
Joined
Apr 29, 2013
Messages
3
Re: 80's 25hp Johnson lost power after battery terminals hooked backwards

Thanks for the information I will check this immediately and repost my findings.
 

walleyereaper

Recruit
Joined
Apr 29, 2013
Messages
3
Re: 80's 25hp Johnson lost power after battery terminals hooked backwards

I checked for spark on both cylinders and both do have spark, all wires appear to be fine, do you recommend testing the rectifier??
 

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,129
Re: 80's 25hp Johnson lost power after battery terminals hooked backwards

Yep.
On some motors a broken rectifier seems to disturb the electics
 
Top