High Temp Alarm

[MCKAYW]

I have an '84 Yamaha 70HP that runs well <br />1)at continuous trolling speed,<br />2)at continuous planing speed<br />But, after running at planing speed when slowed to idle, alarm comes on. After immediately shutting down motor it takes ~10-15 minutes for alarm to turn off. Have changed impeller. Still happens with new or no t-stat. Water comes out the pee hole. It's hard to tell if motor is actually hotter than normal during occurance. Suspect partially blocked cooling channels. Is there a way to power or chemical flush? Do I have to dissasemble the power head? Are the cooling channels accessible or buried internal in the castings? Other items to check?

 

[edodds]

Re: High Temp Alarm

arubasurfer, i would try a chemical flush. Remove the Lower unit, remove the thermostats-but put the covers back on--and fill up a tub with 1 pat acid (boat bottom cleaner) to 4 parts water. Now just get any old bilge pumpand rig it up so that one end (make sure it is the end sending water) fits on the water pick up tube, and that one end comes off the pump into the tub. Do this for about 15 minutes, then when the motor is through draining, repeat. Do this about four or five times, then do it with freshwater a couple of times when you are done. Tip throw your thermos in the tub, that way they get a good cleaning as well. A small water trough works well for this check your local feed store. I would do this once every 100-200hrs, especially if you run the motor in saltwater, just be sure to run freshwater through it before putting every thing back together. Also depending on the condition of you therm gaskets you might want to get some new ones, to have on hand, in case the old ones tear.

 

[MCKAYW]

Re: High Temp Alarm

edodds,<br />Thanks for the info. Late getting back. It's cold here in MA. In your suggestion, do you have to drop the lower end, or can you just run the engine with the chemical bath in a tub?

 

[edodds]

Re: High Temp Alarm

No, you must drop the lower unit. Then on use any old bilge pump, and fit a hose on one end (pick up end)place it in the chemical tank, and the other end the side that shoots water out, fit it to the water pick up tube, that runs up the intermediate housing up to the powerhead. Remember to remove the thermostats, but put the covers back on. You do not even turn the engine on. Hook the pump up to a battery, and flush for about 15-20 min. then stop until it is through draining, then repeat several more times. Remember it is critical that you run freshwater through it severak times at the end, just empty your tank clean it out and fill with water. Also, this may be a no-brainer, but i will mention it, place the tank under the motor so all the water that drains out will fall in to the tank so you can reuse it during the flush treatment. If you have any more questions, do not hesitate to ask, this is fairly easy, but a mechanic wil charge you a hefty price for it because it takes about two hours.

 

[MCKAYW]

Re: High Temp Alarm

edodds,<br /><br />Thanks again! I'll give it a try when it gets warm enough here in the frigid Northeast.

 

[jjdluz]

Re: High Temp Alarm

edodds,have u hear about use vinager to clean the cooling system?and u think boat buttom cleaner work better?

 

[vanner]

Re: High Temp Alarm

I had this problem on my 70 hp yam also. the fix i came up with was to pull the waterpump apart and look at the gaskits. they are not a good fit and need trimming as they hang out inside the water channel and impead the water flow. use a extoknife and beware the gaskit will wont have mutch left on it

 

[bowhuntrrl]

Re: High Temp Alarm

Also check the poppit valve if it has one. Yammy's are known for that symptom with P valve problems.

 

[vanner]

Re: High Temp Alarm

would like to be more clear on my post yesterday I run a mid 80s 70hp yamaha. The guy I bought it from had a hightemp alarm at low speed or idle but it did not go off at planing speed or w.o.t.it also had a good tel at the p hole, at first he tryed the impeller that did not work so he thought it had an obstruction in the water circuit and tryed pulling the head and exaustmanafold and just busted his but trying to fix this thing I dont remember just what he did that made him think he fixed it but I ended up with it in the spring and as the water started heating up the problem came back Mckayw if you pull the t stat housing and it looks clean take a look at the gaskets on the impeller housing that gasket should be even with the insides of the channell or the water will cavatate at low speed. I think a dremel tool would clean that up good but I did not have one then.good luck