Updates to the build....
I sold the 25HP Mercury on Craigslist and found a good deal on a used 40HP Yamaha at a local marina. Brought the Yamaha home, and installed it, and fired it up and it ran great. I immediately took it to the lake and took it out for a test run.
The motor ran great, was pumping water good and made plenty of power. After about 10 minutes, the overheat alarm went off, and I looked back and no water was pumping out of the telltale.....? I let it cool off, and restarted it, and still no water pumping. Had to be towed it. Really frustrating. Took it home and I pulled off the lower half and the impeller looked to be in great shape. Next I pulled the water line from the motor to the telltale and found it had salt & crud in it. Lots. Blasted that out. Restarted and water was pumping great again. Problem solved.
Took it out in Puget Sound to do a little crabbing and fishing and sure enough, after 10 minutes it was overheating again and no water from the telltale. I was baffled because it pumped water fine at home on the hose, and great when we launched it. For some reason it would quit though....? Ended up limping to the beach and calling for another tow.
Got it home and decided to tear into the motor more. I pulled the thermostat cover and exhaust manifold cover. Lots of salt and crud. I scrubbed all that out and rinsed and blasted out all the passageways with compressed air. I reinspected the impeller and it looked great. Also replaced the thermostat. Reassembled and ran it on the hose and it was pumping water better than ever. In the meantime, never wanting to be towed in again, I scooped up a small matching kicker motor on craigslist.
Good thing too. Because guess what, after another 10 minute test run in the lake, the 40HP Yamaha was overheating again. At this point, I was completely baffled. The inside of the motor was clean, no obstructions at all. Water pump impeller looked great. I was ready to scrap this motor and find a new one. I decided as a last ditch I would replace the impeller and whole water pump assembly, even though it looked fine. I disassembled the pump and removed the impeller and saw this...... see what's missing?
No key was installed between the impeller and driveshaft! So it seems like the impeller would spin and pump while it was cold, then once warmed up, it would start to slip. Super irritating because I had looked at the impeller several times and never considered that someone could have left out the key. I replaced it, and ran it on the hose, and now it really pumped water! Took it back out in Puget Sound and it ran great all day. Problem solved!
Next projects:
1. Relocate the kicker to the port side and mount it on a drop down bracket. Also need to add a steering connection to the main motor.
2. Relocate the fuel tank and battery to the front of the boat to even out the weight.