Thanks for the info:
The information you suggest on glow plugs is similar to my experience on tractors. I have a tractor I have had for over 30 years and never replaced the glow plugs.
I'm a bit new to boating
so thought it might be different.
I tested the 4 glow plugs of this engine earlier as you suggested. None warmed up. I used the jumper clamps that came with one of my inverters. I screwed the positive end to the top of the plug
using the thumb screw and washer that had been cleaned and brushed. I used a small vice grips to hold the other end onto the body of the plug.
When I found your reply I just got done doing it again I also hooked up the leads to the inverter
just to make sure they were good and the inverter
worked just fine with them hooked to the same battery attachment points.
Any suggestions appreciated. At this point it seems my glow plugs are bad. I just got the boat a few months ago and it starts poorly so i have been trying to figure out why.