Hypothetical Question about muffs

[bds85466]

What if...you ran your motor without muffs? How long would it take to overheat or damage something?

Question 2, is the water exiting your motor pee pee hole supposed to be warm? Like 80-100 degrees or so?

 

[BF]

Re: Hypothetical Question about muffs

#1 Not long. Anything above 15-20 sec and I'd start being worried. In most service manuals they have pict's of how impellers look when they've been run without water. IIRC, by 30 or 45 sec, they start looking deformed/cooked. The impeller is rubber and spinning in a tight enclosure (rubbing the sides). Without water it overheats quickly (way before the engine overheats). If the imeller is cooked, the danger is that next time it is run on the water, the engine overheats and has major damage.

#2 I think depends on the motor and where the tell-tale is plumbed.

 

[rndn]

Re: Hypothetical Question about muffs

Rubber running directly on metal?? Not a good idea for even a few seconds. Bottom line is you should ALWAYS have water available when running your motor, whether it is in the water or being supplied thru muffs. You could also cook your powerhead or many other very expensive items in a very short time.

 

[tashasdaddy]

Re: Hypothetical Question about muffs

i have seen impellers go in less than a minute.

 

[dingbat]

Re: Hypothetical Question about muffs

i have seen impellers go in less than a minute.

Much lesss than a minute. A few years back I had just installed a new impeller and started the motor by accident without water..... don't ask. :redface:

Ran for maybe 10 seconds and the rubber had melted to the inside of the pump housing.

 

[AguaSki]

Re: Hypothetical Question about muffs

Often in the make ready area I will see a genius skipper attempting to start their engine with the boat still on the trailer. My guess is that the skipper thinks running the boat dry for a few moments will help with a quick launch once the boat reaches the water. This is usually the same guy you see at the end of the day running the motor again with the boat on the trailer to flush out water.

I always took everyone's advice and only ran my motor with a water supply, but after I rebuilt my first water pump, I was able to see how the impeller worked. Once I saw and understood the mechanics of what the impeller is doing, I was even more determined to never run the motor for even a brief second without water. Rebuilding a water pump was a great lesson for me, and prevents me from making the same mistakes I see every time I launch.

 

[tashasdaddy]

Re: Hypothetical Question about muffs

agreed. i always, start mine at home, on muffs, before leaving for the ramp.

 

[jtexas]

Re: Hypothetical Question about muffs

ok, say you back down the ramp, crank awhile, figure it won't start and pull out.

During the course of your troubleshooting, you do some more cranking and the motor eventually starts. You shut it off right away and go fishing.

My theory is, the water pump is wet from your initial attempts, so you haven't done any damage.

Agree or disagree?

 

[tashasdaddy]

Re: Hypothetical Question about muffs

it does not take long for the impeller to get hot. you may get lucky, but you are definately shortening the life of the impeller.