Overheating?
Shallowminded
Posts: 58 Greenhorn
Yamaha f40 runs fine at idle. From the time I put the boat in the water, and idled to the end of the no wake zone was 15 mins. I take off, got up and running @4500 rpms for a mile or so, overheat alarm goes off. The tell tale was flowing fine, water coming out wasn’t hot at all. Impeller was changed last year around May. Before I tear into this, I’m thinking thermostat? Any other thoughts?
Replies
larrywitt
The T-stat is a moving part. For over 30 years when I run any of my boats (always in salt) I flush the motor, and have at the ready near the hose, a bottle of auto transmission fluid. After flushing for a minute or three, I shut off the water and quickly unscrew the hose and pour a tad of the **** fluid in it, then reattach and turn the water back on. It will exit the engine in a pink froth. Feel it, if you can. That slickness is also on your impeller and thermostat.
I once went six full years on a Johnson 150 T-stat when doing this, and decided it was due for an impeller..... I changed it, but the old one looked and worked just fine.
**** Catri taught me this trick.
I now know why the chicken crossed the road.....
It was to show the Armadillo and the Racoon that it could be done.
Did you notice a lot of crud come out when you did the vinegar flush? I overheated once at WOT a few weeks ago, so I changed my pressure control valve (poppit) and thermostat at the same time and started flushing with saltaway. It ran great for a couple weeks but now I'm getting a consistent overheat at about 5000 rpms. I'm thinking the saltaway may have broken down some stuff that got clogged further down the water passages.
I'm the first person I've heard of that started having overheating issues after doing the thermostat, poppit and saltaway.
The water isn't coming out the tell tale hot when I'm overheating now. It definitely was when I overheated a few weeks ago before doing the thermostat/etc.
When I did the vinegar flush the water had a greyish mirk to it but no hardcore sludge. I've used salt terminator before on flushes and ran it at boat ramps after salt water use so i don't think i ever had a multitude of gunk built up to speak of. When we took it out on lake harris I spent ample time putting it through it's paces to make sure the issue was solved. I have my boat listed on here and on CL for sale and I wouldn't sell it if it had any mechanical issues.
What I would do is another flush if I were you, might be a good idea to do a vinegar flush but turn the motor off and let it sit for say 30 minutes, then run it again, then sit 30 min then run again and then flush with fresh water.