engine vibration due to alternator?

[jim wick]

pair of 6cta/s running great, port started to vibrate at 1600 rpm, off and on. did not notice hitting anything.

shaft seemed smooth/balanced to the touch under way. engine had a noticeable intermittent vibration

back at the dock she had a small squeal coming from the alternator shield

all wheels including the alternator spun very free, belt is two years old with a little residue on the engine

1. would the alternator act differently when it is asked for voltage? (not spin so freely)

2. a new belt is a cheap way to start unless I can troubleshoot the alternator under voltage draw conditions. good or bad idea?

3. do you think I have two problems all at once or is the squeal related to the on/off again vibration?

Now that I think about it, maybe the vibration is intermittent because the alternator is intermittently getting asked for voltage? It seems like a little alternator would not be able to make that big engine rough…..

Topic

[Tony Athens]

1) Let’s “see” some good clear & in-focus pics of all the “things that turn” with that belt on the front of the engines..

2) How old “Marine Age wise” are those “things that turn”– You have a coolant pump, alternator, fixed idler and spring idler……….

3) You asked about the alternator– How old is that–Total Hours and “”Marine Age” wise. When an aternator loads, belt slippage can occur.

Let’s start with that.

Tony

[Author]

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