I have two questions concerning my Yamaha 9.9 four-stroke outboard.

First concerns possible overcharging from the alternator and what to do about it.
The alternator has a max output of 10 amps. Even feeding a bank of two wet-cells
in parallel, that's a lot of current to feed in over an extended time. The batteries get
up to 14 volts and possibly higher. Will this high charge rate hurt the batteries, although they
will build up resistance as they charge up? Would there be any damage to the alternator if it were
disconnected from the batteries at any time?

Second question concerns the susceptibility of this engine to develop blocked jets
in the carburetor. Although I have and inline filter from my tank and another filter
in the engine fuel line, I had to clean the jets today after doing the same job a month
ago. Although I did not use the engine hardly at all in the interim, I was made sure
to run it for a few minutes every week, but it got progressively worse. My gas is
typical gasohol, which I bought the beginning of the season. About mid season I
added a carburetor cleaner and gas preservative to the main gas tank. Both my filters do not look
very dirty. Pulling the carbs and cleaning the jets is a half day job,
so this is getting a bit tedious. Maybe they will someday design a carburetor with a
built-in cleaning mechanism, like a needle plunger which can be operated without pulling the carbs.
Seems like these types of carburetor problems are almost an
epidemic, as engines are lined up at my mechanic for this same problem. Four strokes are especially
susceptible to this problem because of their fine diameter
jets. Any ideas on how to minimize this problem?

sherwindu wrote:
I have two questions concerning my Yamaha 9.9 four-stroke outboard.

First concerns possible overcharging from the alternator and what to do about it.
The alternator has a max output of 10 amps. Even feeding a bank of two wet-cells
in parallel, that's a lot of current to feed in over an extended time. The batteries get
up to 14 volts and possibly higher. Will this high charge rate hurt the batteries, although they
will build up resistance as they charge up? Would there be any damage to the alternator if it were
disconnected from the batteries at any time?

The typical 12-volt system doesn't really operate at 12 volts, your
reading of 14 volts sounds normal with the engine running. The
alternator is designed to operate with a load (the battery), but I
suspect no damage would occur if run briefly without that load.

Second question concerns the susceptibility of this engine to develop blocked jets
in the carburetor. Although I have and inline filter from my tank and another filter
in the engine fuel line, I had to clean the jets today after doing the same job a month
ago.

With two fuel filters in place I can't imagine any solid contaminant
getting through, so I would suspect a reaction between the gasohol, the
carb cleaner, and the fuel preservative. Can you identify what is
blocking the jets? I'd drain the tank and try fresh, straight, gas.