What Now?

[pallen58]

After a wonderful summer we are looking forward to fall sailing. The A4 has been a real champ for us this summer. It started and ran every time we asked it and even handled a storm. After a new fuel system, carburetor and water pump the skipper, (wife) was so confident that it would run that she has taken thr boat out herself for some single handing.
So what now?
After I changed the water pump it got to engine temp, 180, and all was good. After a couple of trips the temp would not come up, stayed right on 140. Not a huge deal but I began searching this site for fixes. I also noticed that there seemed to be more exhaust. I was getting ready to pull the thermostat when I noticed the #4 spark plug connector was not seated and could of been considered off. I pushed that back down hard and the engine fired right up and went to operating temperature (180) and the exhaust was back to normal. So does only running on 3 cylinders have that result?
Late last year I put a new solinoid on. Yesterday the engine was not starting. My engine guy was on the boat and he suggested that we tap the solinoid and starter and he did the tapping. He suggested a new solinoid. Do those only last a year? The starter was also re-built within a year so they are both new.
What are thoughts on both of these.

[hanleyclifford]

From your narrative it is clear that running on only 3 cylinders has several bad effects - reduced heat generation, unburned gases in the exhaust not to mention reduced power and increased fuel consumption. As to the solenoid: before replacing it (again) make sure all battery cables and terminals are sound and that the path from the engine block back to the battery negative is present and adequate.

[ILikeRust]

So does only running on 3 cylinders have that result?

I would say your evidence indicates "yes".

But sure, it makes sense to me. Three cylinders firing will produce less heat than four. And you'll have unburned fuel coming out the exhaust.

Late last year I put a new solinoid on. Yesterday the engine was not starting. My engine guy was on the boat and he suggested that we tap the solinoid and starter and he did the tapping. He suggested a new solinoid. Do those only last a year? The starter was also re-built within a year so they are both new.

Question might be whether the solenoid is "bad" or just needs a little lubrication or tweaking.

The solenoid should last far longer than one year.