2004 BF 150 Overheat Alarm

[Honda BF 130]

Hi All,

I recently installed a used 2004 150 on my 21' deck boat. Motor has approx 450 hrs on it. Got it rigged and propped and it was running nicely. We went out through an unfamiliar channel and I hit a limestone rock at about 25 mph which stopped the boat immediately and left a quarter sized hole in the gear case which leaked out lower unit oil immediately. It started overheating after that happened. I purchased a used lower unit, changed the impeller, and the thermostats on the motor. Took it out and it was running great again. Went out 15 miles, running about 18 mph with a full load of people and gear. Turned around to come back to shore and as soon as I would try to get on plane the overheat alarm would go off. I slowed down and it was happy running at lower rpm, no alarm initially. After a while, the alarm would sound within 30 seconds of turning the motor on. As is right now, within 30 seconds of starting the motor for the first time today, I get the alarm so the motor isn't even warm and the overheat is sounding. I purchased a new temp sensor, and I have tried it in the 3 connectors that I can find. 2 at the thermostat, and 1 in the block on the starboard side next to the oil pressure sensor. I plugged the wire harness into the new sensor in all 3 of those places, (didn't install the sensor into the engine, just plugged it in) and I am still getting the alarm. The telltale is making plenty of water and the new stats are opening up.

I did have a loose battery connection and my voltage gauge was hopping between 14 -17 volts until I realized what was wrong last time out. I'm worried I might have messed up the ECU. I was told since it is an 04 that there's no way to hook up to it to get codes. I am fumbling in the dark at this point.

Any suggestions are appreciated.

 

[Honda BF 130]

I back flushed the motor with the lower unit off from the stats down and caught the water in a 5 gallon bucket. Maybe 1/2 teaspoon of sand came out after 5 minutes flushing through block and head stat openings. There are no obstructions in the hoses which leave the stats. I can blow air into small hose which leads into the poppet valve and it appears to be open with no obstructions. I don't want to open it up because the bolts which hold it shut are corroded. I put everything back together and it is doing the same thing. Immediate overheat alarm and shut down. I checked the lower unit intake and there is nothing in there either. Looking up at the hose which comes from the impeller housing into the bottom of the block the hose is connected, not kinked and everything seems to be tight. Given the immediacy of the overheat alarm upon starting, I am guessing something electronic is wrong and at this point I am thinking I messed up the ECU.

 

[Honda BF 130]

Update. I think I solved it this morning. I couldn't find the 4th water temp sensor that was being discussed (ECT). I had found the 2 on the thermostat housing and the one on the block. I missed the one in the exhaust/ muffler at the top on the back of the motor. Checked the ohms and I got 600. All of the other sensors registered between 1200 and 1400 ohms cold. Popped a new sensor onto the connector and so far no overheat alarm. I'll post again if it's not fixed.