Re: Force 70HP 1992 - 20A Fuse blows while running?
I see no one has replied yet so I'll try and help.
If I'm looking at the correct wiring diagram, you have the HP type II ignition system?
According to the diagram, the 20 amp fuse is inline on the red and purple wire. Red wire with thin purple line (known as tracer color). That wire is your main ignition wire to the ignition switch from the starter relay.
Correct me if I'm wrong but it looks like that wire attaches to the starter relay at the same connection as your positive cable directly from the battery? If so, that wire is the battery voltage feed wire to the ignition switch.
The problem is that there is also a solid red wire at the same connection on the starter relay that ties into the rectifier, stator, and switch box.
So I would start by looking for any chaffing or breakage along the entire length of either the red/ purple wire and the red wire where they could be touching other bare wires or grounding to bare metal. Also look closely at the back of the ignition switch. Hope you find the problem here. If not you're going to have to get into more advanced diagnosis.
In fact check all the engine wiring for shorts to ground, burned marks, damage, etc. Check up under the stator for any burn marks to windings and wiring and the rectifier wires. The fact that you say it happens while it's been running is what makes me think you might have other issues. But don't worry, anything is "fixable".
BTW, do you have an amp/battery gauge on this boat? Are you "over charging" after running the engine for a few? Are you leaving a battery charger connected to the battery for long periods of time when you're not using the boat?
Let us know what you find and report back. BTW- My advice is not to run this boat until you resolve the issue. Depending on what the problem is, you could run the risk of frying your whole electrical system. Also, DO NOT replace the 20 amp fuse with a bigger fuse.
