1990 Baja Islander 190
 

I have a 1990 Baja Islander 190 with a 4.3 having a couple issues with it wondering if anybody could help me out. The first issue I'm having is the charging system I have a single Deep cell battery which is brand new but according to the guage I can't get past 12.5 volts so as soon as I crank the radio up it cuts out. The second issue i'm having is at idle the temp gets up to about 220-230 but as soon as I hit the throttle it goes right back down.

This question might get better answers in the technical discussion area.

Now, with that disclaimer out of the way....

Regarding the battery issue, think of the battery as a storage box for energy. The alternator fills the storage box.
That alternator should be internally regulated, and the average alternator charges at a rate of 13-14v. Your guage may not be accurate, because when the diode/regulator goes, the guage will show a gradual loss in volts or a reading above 14.4v.
If the radio is cutting out while the boat is running, check the size of the ground and power wires, as well as the connections. If it cuts out when the boat is off, you may have to invest in a "lightning cap" (capacitor).

Regarding the overheating at idle, I'm guessing the boat is an open system (seawater cooled), and you are due to replace the impeller. Also, check for kinked hoses around the motor, manifolds, etc. If the impeller was just replaced, it's possible a broken impeller blade or other foreign article is restricting water flow.

The first step in resolving these issues yourself is obtaining a Mercruiser service manual.

http://mercmanifold.com/images/im3909h.jpg

http://www.grandvalleymarine.com/Mar...es/862031T.jpg

Thank you for the advice I took the alternator off last night and I'm going to get it tested today.

Alternator was bad that's fixed. Tonight i'm going to look at the impeller