Run-Dry impellers

[jcollins]

Over the years I have been told to NEVER start the engine dry. Now I find this product.
Anyone have one?

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

Interesting product line: http://www.globecomposite.com/pages/products_marine

[jleonard]

I never had one. Two boaters (that I trust) told me they tried them and they burned up in seconds.
Therefore I do not have faith in their claim.

[twomey]

Last season I installed one of the Globe impellers after reading some positive reviews. On the last day of the season I changed the engine oil and fuel filters while on the mooring. When I finished, I tested the engine. All was well and I went home to clean up before moving the boat to a nearby marina where it would be hauled in the morning. Normally, I shut off the raw water intake when leaving the boat, but I was tired and in a hurry and forgot.

When I returned the wind had picked up, it was dark and starting to spit a cold rain. As I rowed out to the mooring, I was thinking about navigating the narrow dredged channel to the marina haul-out dock and then getting the boat secured to the dock in the wind. I got back on the boat, opened the hatch and opened the raw water intake... But what I really did was close it since I had accidentally left it open earlier. I was so focused on other things that I didn't even notice that I was pushing the valve down instead of lifting it up. I then closed the hatch and started the engine. Normally I check the exhaust to see if water is exiting, but it was dark, cold, I had already checked the engine just a couple of hours earlier, etc... I left the engine idling for 5-10 minutes while I secured the dingy and unhooked us from the mooring. I then traveled 1/2 mile down the river and then 1/4 mile up the narrow channel to the dock. I doubt if the engine was ever run at more than 1000 rpm during the trip. All when well and after I secured the boat, I shut off the engine. It was then I smelled that smell of an overheated engine. The engine was overheated, but just shy of the alarm point. I tested the engine with the raw water intake open and everything seemed to be working normally. After the boat was hauled I pulled the impelled out. Most of it looked pretty normal, but about 1/4 of the blades showed some damage.

My past experience with an impeller running dry happened when the raw water intake was blocked by debris from the outside while the engine was running near cruise speed. In that case, the engine was shut down within seconds of hearing the temp alarm, but the impeller had already disintegrated into many small pieces which managed to end up all through the cooling system and cause other issues later on.

Maybe any impeller would have worked as well as the Globe one, but the Globe did survive my carelessness. If the engine alarm had gone off while in the dredged channel, I would have been faced with shutting the engine off, which surely would have meant grounding the boat at night with the weather going downhill or continuing on knowing that you might be doing some expensive damage. So I got a new Globe for this season. I doubt if any impeller, Globe included, could survive long if the engine were running at high rpms.

Tim