Overheating problems?

[bevansh]

I have a boat with an 80 HP Mercury outboard motor that I got last year to ski and tube with. Every time that I take it out, we run it for about 45 minutes to an hour and a half, and then it almost seems to "die". It loses all of its power, and we cannot go full speed. I have no temperature gauge on it, so I'm not sure if it is overheating. I tend to think that it is overheating, and that is why it has trouble after we run it for awhile, because it always runs great when we first put it in the water each time. If it is overheating, I wonder if it is due to a bad impeller?? I have not replaced it, but when I start the engine up, it pees out a nice stream of water immediately, so maybe it isn't the impeller. Or maybe it isn't heating up at all.<br /><br />Any ideas??

 

[oldboat1]

Re: Overheating problems?

I wonder if you might have a problem with your fuel tank. You must have the vent open or the engine would die much earlier. But as the fuel level in the tank goes down, maybe the engine is not able to get gas? On a full tank of gas, does the engine behave normally when hot?

 

[bevansh]

Re: Overheating problems?

I have a 10 gallon tank, and the same problems happen even when I start with a full tank. By the time the problems start, the tank is probably down a couple gallons. But it is still pretty full at that point. <br /><br />I also thought I might have had alcohol in my gasoline mixture that was causing boiling in the fuel lines and overheating, but I now use BP gas, which isn't supposed to have any alcohol, and that didn't help any either.

 

[Franki]

Re: Overheating problems?

If you want to check for overheating.. <br /><br />next time you are out and about and just before you get to the point where it seemingly overheats, whip the cover off and touch the cylender head.. (do it carefully in case you are right. or check it by putting a drop of water on your fingertip and drip it onto the heads, if it doesn't sizzle, then try your finger.)<br /><br />you should be able to touch the heads for a slow 5 count.. if you can't its too hot..<br /><br />if the engine case and head are smoking, its too hot.. (much)<br />if your head and block have turned black and are crackling.. then its wayyyyy to hot..<br /><br />Find out if it is actually running hot before you stress about why..<br /><br />rgds<br /><br />Frank

 

[bevansh]

Re: Overheating problems?

Thanks for the tips oldboat1 and Franki-ESL10072. I'll try them and see if we can't figure this thing out.