1988 Mercury 70hp overheat?

[christopher1]

I have a 88 Merc 70 hp that has been well taken care of (owner since 2004). I am not mechanical but have repairs/upkeep done by repair shop. Have not used the boat in a bout a month and could not find my muffs to run it ( since it is an older motor/boat makes me feel better when it runs well...always done) Could not find my muffs so went out and bought a new pair. Ran the engine and put it in gear 1/4 throttle ( I now know not good to do) Overheat alarm went off for first time ever, shut her down. Started up few seconds later and alarm was still on...put back in garage.

Question is......water was peeing constantly but now looking back the new brand of muffs probably did not supply enough water since in gear.

Can a one two minute overheat do major damage?? I baby the engine because it is old (88 bass boat looks brand new)......Looking for some reassurance.

Thanks

 

[sschefer]

Re: 1988 Mercury 70hp overheat?

One thing about two strokes is that any overheat alarm situation takes a toll on the engine. It may not be severe enough worry about but you took some hours off the total engine life for sure.

Hope I didn't scare you too badly. Yes it probably did some permanent damage but it will probably be fine if you find the problem and fix it so it doesn't happen again.

The first thing you want to do is pull the lower unit and change the impeller. Don't even bother to think about why, just do it.

I run my big motor and my little ones in a pasture trough that I got at a local farm supply. It's deep enough to submerge the L/U and I can test with or without the muffs. I don't have to worry about having enough volume comming out of the hose this way and I can truly see if the pump is working correctly or not. I welded a hose bib on the side near the bottom and I drain it into the garden when I'm done.

I have had critics tell me that I'll suck up oil into the cooling system. Heck I get more oil than that ideling around waiting for a spot at the fuel docks. So to that, I say baloney.

 

[christopher1]

Re: 1988 Mercury 70hp overheat?

Thanks for the response

 

[Jacket4life]

Re: 1988 Mercury 70hp overheat?

How long did you run it before the alarm went off?

 

[christopher1]

Re: 1988 Mercury 70hp overheat?

I would say max 3-4 minutes...maybe 2 minutes in gear (I now know not smart) I was always taught that if water coming out of pee hole you are good. Alarm went off for maybe 10 seconds put in neutral....water not hot...shut down.

 

[Jacket4life]

Re: 1988 Mercury 70hp overheat?

Did you happen to put your hand on the cowl? If you did, and it WASN'T hot, you may have a faulty alarm, not an overheating problem. That doesn't sound like long enough for it to have reached 220, which is what I THINK the overheat is set at. (Someone on here can tell you that for sure) BTW, the instructions for my muffs and in my Clymer say not to run over 2500 RPM, 1/4 throttle should not have been that high. If you still had wayer at the telltale, the I doubt you exceeded that anyway. The deal is, on the muffs, if you run too high RPM's, there isn't enough force being generated by your hose to maintain a constant stream, so the impeller 'sucks air' then picks up water, so on and so forth...I'm really thinking you may not have overheated at all...

 

[christopher1]

Re: 1988 Mercury 70hp overheat?

I hope that is all I did. I took it in to the shop and have not heard back. I wish I could do repair/maintenance. I told him to check themostat etc. It was one of those days I wanted to head to the lake (45 minutes) away. I think these new muffs I bought and the scenario you mentioned of sucking in water and air is the culprit. Amazing how you fall in love with old boats and dump money into them.

 

[christopher1]

Re: 1988 Mercury 70hp overheat?

In response to above question I did put my hand on cowling but really have nothing to compare it to as far as temperature?????