I thought this was a bad Idea...

[Daver29]

OK, fairly new to boat ownership so I still watch everyone at the ramp while I'm there to get ideas to improve efficiency and 'what not to do'.

I see quite a number of guys who start the boats up in the staging area (some for longer than others). Now I understand starting on muffs before you leave the house, just to make sure she's not gonna go finicky on you; but I always thought running them 'dry' was bad for the I/O impellers...?

Just wondering, am I uneducated or are they?

 

[04fxdwgi]

Re: I thought this was a bad Idea...

OK, fairly new to boat ownership so I still watch everyone at the ramp while I'm there to get ideas to improve efficiency and 'what not to do'.

I see quite a number of guys who start the boats up in the staging area (some for longer than others). Now I understand starting on muffs before you leave the house, just to make sure she's not gonna go finicky on you; but I always thought running them 'dry' was bad for the I/O impellers...?

Just wondering, am I uneducated or are they?

1st rule. Never run without water. It will roast the pump impeller.

 

[Friscoboater]

Re: I thought this was a bad Idea...

That is one thing I rarely see. Yes that is a horrible idea.

 

[H20Rat]

Re: I thought this was a bad Idea...

but I always thought running them 'dry' was bad for the I/O impellers...?

Not all I/O's have impellers in the outdrive. Some use an engine mounted water pump that is somewhat more tolerant of running dry. (Anyone know which I/O's use which?) Also, all true inboards use engine mounted pumps.

Most jet boats use a line tapped into the high pressure area in the jet pump, they have no water pump other than that. Running them dry is usually fine other than the fact of the engine heat building up.

 

[04fxdwgi]

Re: I thought this was a bad Idea...

On Mercruisers, the Bravo drives all have engine mounted pumps. They may be a little more tollerant to being dry, but not for long. If he doesn't have a jet drive, then refer to rule #1

 

[MAXXIE]

Re: I thought this was a bad Idea...

I will run the motor on the muffs every now & then at the house. The only thing I might do in the staging area is just bump the key to make sure I have power, I would never run the motor out of the water. Just like 04fxdwgi said, You'll smoke the impeller real quick without water. I would just watch those other guy's & laugh or You should walk over to those guy's & let them know, they may have no idea the damage their doing to their engine's.

 

[ezmobee]

Re: I thought this was a bad Idea...

The only thing better would be if they were doing it with I/O's with the drive tilted all the way up

 

[seaboo]

Re: I thought this was a bad Idea...

jet boats, and jet skis it's fine to crank without water. A boat with a closed cooling system maybe (never owned one and I do not know). A boat (i/o or outboard) BAD idea!!!!!!

 

[Daver29]

Re: I thought this was a bad Idea...

Thanks for the confirmation guys. Wanted to make sure I knew what I thought I knew. I didn't pay attention to type of I/O, or if they had it up or down... just knew that running it dry was not a good idea.

 

[robert graham]

Re: I thought this was a bad Idea...

If you ever notice how tight those impellar blades are inside that stainless steel pump cup, then it's easy to imagine how quickly heat would be generated during a dry start. I'll bump the key to check for power, but never start it up. Hang around a ramp and you'll see lots of stuff that'll raise the hair on back of your neck! Good Luck!

 

[04fxdwgi]

Re: I thought this was a bad Idea...

jet boats, and jet skis it's fine to crank without water. A boat with a closed cooling system maybe (never owned one and I do not know). A boat (i/o or outboard) BAD idea!!!!!!

Even with the closed cooling, there is still a raw water pump to pump the raw water to the heat exchanger, same as a raw water cooled engine.

 

[superbenk]

Re: I thought this was a bad Idea...

Here's why you don't run them dry:

 

[jmarty10]

Re: I thought this was a bad Idea...

I saw the best of both worlds last Friday. Guy on a lift starting his boat with motor all the way up and out of the water. Livin dangerously

 

[Fireman431]

Re: I thought this was a bad Idea...

They do make a higher silicone content impeller which the manufacturer says it OK to run for up to 15 minutes out of water. I'm sure these guys are not all equpiied with them, just an FYI.

http://www.globecomposite.com/pages/products_impeller

 

[dockwrecker]

Re: I thought this was a bad Idea...

I'm all over this one, thanks fireman! I'm gonna give one a try, not that I run dry, but I'm sick of doing impellor replacements every other year. Yes I said every other year and I know its recommended annually, but it's still a huge PITA at that.

 

[oldjeep]

Re: I thought this was a bad Idea...

I'm all over this one, thanks fireman! I'm gonna give one a try, not that I run dry, but I'm sick of doing impellor replacements every other year. Yes I said every other year and I know its recommended annually, but it's still a huge PITA at that.

Recommended annually? Last time I checked Mercruiser said to inspect it every 3 years. Even after 5 years mine still looked like new when I replaced it last year.

 

[MAXXIE]

Re: I thought this was a bad Idea...

I guess the yo-yo that owned the boat before me didn't give too much thought to the impeller. I had to swap it out mid season last year, didn't even realize it until I added a tell-tail to my Force O/B. Almost nothing was coming out of the tube, thank God I happened onto that thread when I did. This is my first boat & really did not know of such things (that's why I'm a member here). Now with the new impeller I have split the exit tube for the tell tail & get about a 12' stream of water out of both tubes. Looks kind of cool & I get a lot of strange looks at the launch when I fire it up.

 

[Fireman431]

Re: I thought this was a bad Idea...

I replace mine every 100 hours, without fail. It's strange, though. I have pulled out impellers with 100 hours on them and they look great (they become emergency spares) and I have pulled ones out with 100 hours and they look like crap, with vanes about to fall off. Same water, strainers working and clean, same temps. I guess there's no common denominator. To me, it's cheap insurance.

 

[ziggy]

Re: I thought this was a bad Idea...

here's mercruisers idea on running w/o water applied... (scroll down to pp 2)
myself, i'm w/ fireman. i R&R my impeller once a year. cheap insurance agreed. + imho. it's a good idea to seperate the halves to inspect other items too.
i try very hard to not run my i/o w/o water applied... certainly never at the ramp till it's in the water...
here's three years of impellers out of my boat.. all have one season on them.

this one got run on low water pressure from the hose. it almost overheated me...

all have a set to them, the one with the most is newest, one year old, the other two are either 2 or three years old since service.
all had creases on the inside of the impeller blades... showing signs of wear...

 

[shrew]

Re: I thought this was a bad Idea...

jet boats, and jet skis it's fine to crank without water. A boat with a closed cooling system maybe (never owned one and I do not know). A boat (i/o or outboard) BAD idea!!!!!!

The impellor still needs to draw raw water to cool the heat exchanger and in most cases the manifolds and risers. When they run dry they heat up and burn out quickly just the same. Then there is little or no raw water to cool the heat exhanger which cools the closed cooling. Still equally as bad an idea.