Hi Roym,
Although a lot of my business' work is with standby generators of 1 Megawatt and larger, I must be honest and say that I don't know a whole lot about small, gasoline generators. My limited experience is with repairing some electric system sections for friends and family, Below is based on what I do know:
The circuit breakers in generators usually have a very specific time/current curve. Installing a fuse in line won't have the same time-current curve. This could cause the alternator windings to burn before the fuse opens. Conversely, a fuse (even a dual element TD fuse) may open on inrush. A standard circuit breaker also won't match, You can ask Yamaha directly for the specifications and search for a generic circuit breaker to suit.
The next best plan would be to search on line for the breaker specific for your machine. You may be able to find a used one. Check also Electrical Advertiser magazine and call some of the many used and refurbished circuit breaker sellers. My house Wacker I bought used with a bypassed breaker. I found the exact one from a seller in that magazine (Salinger Electric) for 12.00 USD- new in box.
I have some experience with the older Yamaha portable generators and they are excellent machines and well worth repairing. I don't know if the newer ones are still made by Yamaha or by a mystery manufacturer, as so many name brands are now.
OR-
Plan B:
If budget allows, buy a nice, new machine for yourself. Get the Yamaha running by any means necessary.
When the power next goes out, sell it on Craigslist, explaining about the non-compliant circuit breaker.
When power goes out, people fight to buy anything. I had an old, trash picked, cheap Generac 5,000 watt with a rod knock, a melted main circuit breaker & much missing wiring. A craigslist ad- stating the problems- brought dozens of buyers offering rather high dollars. I guess people know how to fix little engines and don't mind bypassing breakers.
If You Buy New-
I recommend Honda with a Wacker alternator or Wacker with a Honda engine. Wacker alternators last forever & tolerate a lot of abuse. They use far oversized wiring. Honda engines are premium beauties, especially the small GX series.
If you go with dual fuel or tri-fuel, keep in mind that natural or LP gas will not produce the output as when gasoline. Usually there is about a 9% - 11% reduction. And, if you use LP, you will go through a lot of propane bottles! PS: Avoid Generac.
Please post back how you make out with repairs or with Plan B.
Paul
