1991 Welcraft 186.4.3 mercruiser speedometer not working help?

I have two questions if possable,
First question is,
My speedometer don't work.Where is the sinser?What can I do to fix this as what to look for?(Sinser,Fuse).

Next & last question,
Does these 4.3 mercruiser alpha 1 engines have a thermastat in them?(Example 185/195 thermastats).I'm guessing nr am I wrong?
The tempature guage reads around 200 F.When,idel or running slow.Is this normal?When I go fast of course it goes lower.

Re: 1991 Welcraft 186.4.3 mercruiser speedometer not working help?

Speedometer measures off of a tube that runs from the back of the speedometer to the back of the boat, where it will connect to a "arm" that sticks down below the boat. The speedometer actually just reads pressure. The faster you go, the more pressure is built up in the tube. Since you're not complaining about water coming into the boat, look for a kinked tube. If it was simply cut or something, you would be getting water in the boat.

Yes, there is a thermostat. It's inside the housing at the center front of the engine where all the tubes come off to the risers and manifolds. It is usually a pretty low temp thermostat - My boat runs 145 or so normally. You probably need to replace your impeller. Mine would climb in temp at lower speeds too, but found a bad impeller (it was my first season with the boat). Since replaced, it keeps temp all the time.

Re: 1991 Welcraft 186.4.3 mercruiser speedometer not working help?

Your impeller is a regular item to replace every other year if you run the boat it wears if you store the boat it hardens. So if don't know when it was last replaced it is past due.

Re: 1991 Welcraft 186.4.3 mercruiser speedometer not working help?

"Sensor" . . .not sinser . .

Actually the speedometer gets is pressure from a 'pitot' hole on the leading edge of the outdrive. Sometimes there is a separate pitot unit attached to the transom, as Struc mentioned.. If the hole gets clogged, or the tube leading into the boat is separated, then the speedometer does not work.

So, check out the pitot hole/tube to see what is going on.

BTW- 200 degree temp seems a bit hot . . . so some attention to the cooling system is needed.