Hi guys.
Wanting help to diagnose an overheating issue. The boat is a 1999 bass tracker with a 40hp Mercury 2 stroke. It's the original motor and had no major work done to it. I bought it 1 year ago and it had all 22yrs worth of service paper work done on it. This past summer I only got to take it out 6 times due to having to add onto my house to get ready for VERY unexpected little girl that was on the way. But I had absolutely no troubles with it. I have taken it out 2 times in February with no issues, but barely had it above an idle. Today I took out on a little bigger lake. Opened it up and after about a half mile the alarm went off. I stopped and shut it off. Waited a while and started it up and idled around a while again with no issues. Opened it back up to run across the lake. And again after about half a mile it got hot again and the alarm went off. It is peeing water, maybe not quite as strong as I remember it normally. But still a decent stream. Not sure if it matters. But the local lakes I am fishing are REALLY low so all the docks are sitting on dirt. So you have to beach the boat while I pull the pickup off the boat ramp. When beaching it I lift the motor up as far as I can and still keep it peeing a stream. But it does stur up a lot of mud that I assume is getting sucked into the system.


I have no idea how these water systems work, but am fairly good at working on things. Wondering if I could get a little help for a starting point. Thanks

Rusty Robinson

When was the last time impeller was changed? Hook up water hose to backflush port on back of motor and flush for 5 minutes. Take to lake and op's ck.

Start with replacing the water pump and not just the impeller, need to do the whole kit.

Thanks guys. I will get one ordered. I am wanting to get it up and running good. Heading to Texoma with my 2 boys the end of April.

Might replace poppet and thermostat also.