25hp Bigfoot Overheat

[Wallyg8r]

Got warning horn after five or ten minute run at near WOT, but of course didn't notice until stopped. Shut motor down and warning stops. Restart motor and horn doesn't come back on any time soon. Telltale stream is good, but having trouble getting up on plane, so something is not good. I'm not afraid to work on this engine, and I'm probably a bit handier than the average bear (ten years as an aircraft mechanic and currently an Engineer)A few questions:<br /><br />1) This engine has a thermostat, but where? <br /><br />2) Are any of the aftermarket manuals as good or better than the $71 Mercury Manual?<br /><br />3) With all freshwater use, is corrosion likely an issue anywhere in the cooling system (read the posts on similar troubles)?<br /><br />Thanks,<br /><br />Roy

 

[ehenry]

Re: 25hp Bigfoot Overheat

How old is the engine and have you ever put an impellor in it?

 

[ehenry]

Re: 25hp Bigfoot Overheat

If you pull the cover off and trace the tell tale hose from where it exits the cowling back to where it attaches to the engine, thats the termostat cover. <br /><br />The after market manuals are generalized and cover a number of engines. say from 2.5 hp up to 40 hp. I bought the Mercury manual for my engine and like it way better that the Seloc or Clymer manual that I had.

 

[Wallyg8r]

Re: 25hp Bigfoot Overheat

Thanks, E.F., Probably would have been good to ask BEFORE I ordered the Clymer book! Oh well, I guess two books are better than one. Thanks for the help.

 

[Wallyg8r]

Re: 25hp Bigfoot Overheat

It's a 2000 model, and no, I've never changed the impeller, but I don't know if the previous owner did or not. I sort of paicked here and took it to one of the local shops. They aren't even going to look at it for a week or two", so I figure I have some time to do my homework. The only reason I haven't gone and picked it back up is becuase it was also loosing power. Nother drastic that I could put my finger on, it just didn't want to get up on plane unless my passenger went forward. After that it still took longer than normal, but it did eventually plane.<br /><br />Could this be related to the warning horn going off, or do I have more going on here? If I thought I could fix this with an impeller change and/or a new thermostat, I'd go get it; I'm missing prime walleye fishing here, and it's no longer under warranty.<br /><br />Any words of wisdom?

 

[Wallyg8r]

Re: 25hp Bigfoot Overheat

That's "panicked"

 

[Wallyg8r]

Re: 25hp Bigfoot Overheat

Hey, what do you know...it's still under warranty! Still, I'm concerned about the power loss and whether that could be related to the overheat. Would a weak impeller cause power loss somehow? What about a sticky thermostat? I noticed a little prop damage I didn't previously know about, could I have a spun prop and would that contribute to the overheat/loss of power? How can I tell if it's really spun?<br /><br />Thanks,

 

[Wallyg8r]

Re: 25hp Bigfoot Overheat

Well, my warranty has now expired and I have done the following:<br /><br />Took my boat to the local dealer who couldn't find anything wrong with it and charged me $137 for my trouble.<br /><br />I changed the thermostat, heat sensor, and impeller.<br /><br />I still get a warning beep....beep......beep in the throttle handle if I run WOT and drop down to idle quickly. If I back off slowly, it doesn't do it, and if I shut down for a few seconds, it stops. <br /><br />Any suggestions?<br /><br />Roy

 

[Lasse Lehtonen]

Re: 25hp Bigfoot Overheat

Have you lost only a little of its power or very much? I think that a small loss of power is only a dirty hull or water somewhere inside your boat giving you extra weight.I have heard about ten times when a boat owner says his motor has lost its power, but after cleaning his hull or looking into his bilge (may be water also in 2 hull boat between hulls) most of these people had said that there is nothing wrong with their motor(s). If the powerloss is sudden and you are losing much of power it usually means losing a cylinder.

 

[HSEMJ]

Re: 25hp Bigfoot Overheat

just a question but would this outboard be a 4-stroke model? Generally A beep beep beep on a mercury ob is a oil alarm, either low oil level for a 2 stroke, or low oil pressure for a 4-stroke.

 

[Wallyg8r]

Re: 25hp Bigfoot Overheat

Yes, it's a 4-stroke model. The Mercury manual is strangely silent on what the alarm means. If it's oil pressure, what is the likely culprit, and how difficult is it to fix?<br /><br />I don't think I've lost any power; we added some weight to the boat since last year (to ourselves as well).<br /><br />Roy

 

[Dunaruna]

Re: 25hp Bigfoot Overheat

Is it an EFI?

 

[pwiseman]

Re: 25hp Bigfoot Overheat

2000 bigfoots are not EFI. In fact none of the 25 bigfoots are EFI.

 

[pwiseman]

Re: 25hp Bigfoot Overheat

How much does the boat weigh now? What boat model is it? If you say it is not plaining well, you could be stressing the motor. Might help to know RPMS, speed, Prop info etc. <br /><br />My merc manual had info in the back regarding alarms and what they meant. This was not a bigfoot though.

 

[Wallyg8r]

Re: 25hp Bigfoot Overheat

Over the Winter we added some weight to the boat, and unfortunately, ourselves. I added a battery, trolling motor, Bimini, horn, radio, antenna, power distribution center, and GPS. Probably 100 lbs or more of stuff. Plus we both quit smoking and put on around 30 lbs between the two of us. When I'm by myself she jumps right up on plane, even into the wind, but with another person on board she struggles, and with three we may not get on plane at all (depending on how big the people are). When on plane she will cruise at 5000 RPM or a little less, with maximum at around 5700. I'll have to see what Prop is on her, but 10 X 11 rings a bell. I have a Stingray Jr fin on her, which helps somwhat. I've found that if I back down off the throttle real slow after a long run, I get no alarm; if I come down quick: beep....beep...beep. Very imbarassing.