Logo
FULL SITE MENU

1985 3.0 l

B

bstevens

New member
Hope that someone may be able to help me out here. This is getting real frustrating with our 140 hp Mercruiser. It ran real good for about a half hour after we launched it for the first time this year. Was in the shop and had a new impeller and timing reset with new points. At first she run the best that it has in some time with rpms at 4500 wide open. Then was time to pull the kids around and the boat started falling on its face. Every time you hit the trip switch up or down it would make the motor miss and later on all it would do was 20 mph at WOT. If it stalled then was a bugger trying to restart. Put a Volt meter on batt and it was fine with upwards of 18 volts showing on battery when reved up. But when you hit the trim switch it was really drawing the juice and you could see that fall right off. Trim switches are only few years old and would say if there was a bare spot on those wires that it would blow a fuse like it used to. One of the questions I have is how much Volts should be at the coil? That was only showing like 9 so wondering if its the coil breaking down or where else I should start? Thanks, Brian
 
Re: 85 3.0l

"Volt meter on batt and it was fine with upwards of 18 volts showing on battery when reved up"

Coil voltage is fine. Alternator voltage is over the limit of 14.8 volts which means the regulator is not functioning--get it fixed.

Carb may need some work.
 
Re: 85 3.0l

What would explain the trim switch making the motor cut out then? And if carb it runs so good for 20-30 minutes then falls flat on its face. Thanks for the help. Brian
 
Re: 85 3.0l

If the battery is on its last legs, the "internal impedance" is high. Placing any load on a battery in this state will cause the voltage that the battery puts out to drop to a low value, i.e., engine running, hit switch... big load from trim mechanism causes the battery voltage to drop . If the alternator has been putting out high volts for a long time, it will damage the battery.

The quick, cheap thing to try is to also check for, is a loose or poor connection to the battery or engine block.
 
Last edited:
Back
Top