Trim pump short questions

[airshot]

Today had my first ever electrical issue, for me that is scary, as a toolmaker I can make anything, but electrical stuff is foreign other than basic stuff. So launched my 16' tinnie with 1992 Merc 40hp classic with power trim/ tilt. Trimmed motor down, ready to start....dead... Checked battery ok, started looking at wires going into motor and see a heavy wire pinched and rubbered thru to bare wires and they are touching. It is the wires comming out of the cowl, going down to the trim pump under the mounting clamp. Cut the wires to eliminate any more chance of a short. Brought it home, removed the damaged portion, the 20 amp fuse was blown, replaced that, connected wires back together to test. I know I will need to replace that section but for now just testing. Hooked everything back up and nothing...no trim, no start....battery is 12.8 v. Are there other fuses I don't see ?? What do I check next ?? Please be kind as I am not an electrical wiz, but can follow instruction if in laymans terms. Yes, I do have a factory service manual and can only see the 20 A fuse insidevthe engine cowel. This engine has been perfect since buying it last summer, it is also in near mint condition, stored inside it's whole life. Thanks in advance for any help you can offer !

 

[airshot]

OK...posting an update, bought some new fuses rather than trust the old pkg I had on hand. With a new 20A fuse in the engine the trim does work now both on engine itself and at that throttle control. Push the key and the choke clicks, turn the key and the engine turns over without plugs. This happens only once, then on the second turn of the key the fuse blows. With the plugs in, the fuse blows when key is turned to start.
Without plugs it will turn over, but when you turn the key a second time the fuse blows. The pinion gear is free as does the bendix feel free....by touch anyway. Starter bad ?? Thanks again in advance for any suggestions..

 

[airshot]

Still updating this issue....after fiddling more with this, it appears the fuse is blowing when the starter is engaged. Can starters be tested ?? Or another component that needs tested ?? Just trying to update my issue to give as much info as possible to find a cure.

 

[airshot]

Went out this morning and tried again, another new fuse, put plugs back in and disconnected trim pump...turned over without blowing fuse !! Tried numerous times and all was good. Reconnected trim unit and that worked from engine and remote controls with no issues !! Tried cranking engine and it worked perfect, no blown fuse......so.....what did I do ?? I figure the second shift gremlins must have came in and solved the issue last night !! Took all covers off and looked carefully for any damaged or burnt wires found nothing. Replaced the damaged trim pump wires and all is good... Gonna do some serious driveway testing before going out on the lake.

 

[QBhoy]

Interesting read there. Sorry I’m late to the viewing. Had similar issues (among other and current issues) with my merc. The trim motor heavy duty wires can have a huge affect on lots of things, if compromised. They can damage and short out many other items along the way. From the trim switch on engine and/or the remotes (latter causing issues inside the remotes there after), harness multi plug pins, main power relay, trim sender…also the trim motor can also share an earth with a few things and/or try and earth through the fine metal bonding wire adjoined to the trim anode under the transom bracket. Worth having a look at the latter mentioned their airshot. Just in case that’s been damaged at all. Best of luck with her. Feel your pain currently. Mine has caused so much damage around and to the boat itself

 

[airshot]

Thanks for the update, will be doing a lot of testing before heading out in big water. And thanks for pointing out some places to look !! So far, no signs of anything, everything looks brand new, but will continue looking !