starting a pump dry

[67 baron sprint LD 390 FE]

I've been told both things about starting up a boat with a jet for a few seconds is the it's hurts the pumps and that is doesn't hurt it. Any info about this would help

 

[90 Laveycraft]

brother, starting a v-drive, jet or I/O-ob without H20 is asking for problems....
v-drive - impellor
jet - bearings
i/o - o/b waterpump

Its just grandstanding..........

 

[RiverDave]

I've been told both things about starting up a boat with a jet for a few seconds is the it's hurts the pumps and that is doesn't hurt it. Any info about this would help

I'm not a jetboat guy.. but I don't think anything good could come from it. My friends that are "serious" about jetboats, have historically disconnected the jet, when running the motor at home.

RD

 

[90 Laveycraft]

not a big deal....the jet pump supplies water psi to the motor. Look at your pump and see the 3/4" hose from the pump to the motor.....most have a tee to connect a garden hose.......run it all day..... PM me for pics - if needed.

 

[92 cole]

The most MOST important clearance in a jet pump is impellar to wear ring and impellar to bowl. If you remove the lube things will get warm and metal or aluminum will transfer or flash away. If you run your'e pump dry just put your'e hand by the nozzle at idle and feel the air it is blowing. this is created by tight tolarances that will get hot and do funny things without coolant and lube, WATER. If you choose to run dry for more than a few seconds atleast put as much water to the pump as you can. just keep in mind that the impellar to bowl feels air only. The wear-ring is getting a portion of what it is designed for. I well understand that alot of drivelines are a pain in the ass to disconnect but alittle time will save alot of money for a rebuild. I dont know if you have ever been behind a jet at idle to feel the volume that is produced by a pump but be careful cause at 800 rpm it will knock you down. I personally will not run my boat or any pump boat I have owned more than enough time to assure fire without disconnecting the pump. For more go to berkeley.com reference maintanance and go from there!!!

 

[jetboatperformance]

In a perfect world... one would never run the motor with out the jet in submerged in the water or being disconnected at the driveline or "jetaway" (if your fortunate enough to have one ) , have I ever done this ? of course! will I do it again probably , do we recommend it as a matter of course , no. Here are some things to consider ... the build clearance between the impeller skirt and the wear ring will be around .025 ttl (about the thickness of a piece of good printer paper) , this amounts to
.0125 (12 and a half thousands) at any given point around the circumferance between impeller and wear ring (dis-allowing for pumpshaft and bearing runout) , Given There is a small amount of runout in the front thrust bearing and the desired "allowable" clearance for the tailshaft bushings vs the pump shaft is .004. soooo the impeller to wear ring clearance is actually pretty " skinny" (in a perfect world ) if one simply lites the motor prior to launch for example odds/chances are nothing will occur assuming that the last time it was towed on the hiway or retreived from the shallows to the trailer for example some road grime and beach grit/sand didn't get into that "skinny space" between the Impy and wear ring to start a scoring or galling process . If a guy is going to "break in a cam" for example depending on the condition of the jet chances are there could be some isssues ,don't loose sight of the fact that the impeller will "grow" slightly as rpms increase ( buzzing the motor) so a guy "rapping" the motor on the trailer runs the significant risk of some potential problems . My opinion is still to play it safe ,disconnect the driveline just my 02 Tom

 

[92 cole]

I should have also stated, ask Tom at JBP!!!! But if everybody takes care of there pumps his rebuild business will slow down!!!

 

[Dominator]

Looks like you got it covered here.:thumbsup

 

[67 baron sprint LD 390 FE]

thanks for all of the info guys. I never start my flat bottom with out water, or my old carrera i use to have with a bravo 1. My cole I have now with the jet has the t to connect water to so you can start it with water to the engine and the pump. I've only done it once for about 30 sec at idle to check everything out . Everytime before I take it out i just make sure it fires and shut it off.

 

[90 Laveycraft]

In a perfect world... one would never run the motor with out the jet in submerged in the water or being disconnected at the driveline or "jetaway" (if your fortunate enough to have one ) , have I ever done this ? of course! will I do it again probably , do we recommend it as a matter of course , no. Here are some things to consider ... the build clearance between the impeller skirt and the wear ring will be around .025 ttl (about the thickness of a piece of good printer paper) , this amounts to
.0125 (12 and a half thousands) at any given point around the circumferance between impeller and wear ring (dis-allowing for pumpshaft and bearing runout) , Given There is a small amount of runout in the front thrust bearing and the desired "allowable" clearance for the tailshaft bushings vs the pump shaft is .004. soooo the impeller to wear ring clearance is actually pretty " skinny" (in a perfect world ) if one simply lites the motor prior to launch for example odds/chances are nothing will occur assuming that the last time it was towed on the hiway or retreived from the shallows to the trailer for example some road grime and beach grit/sand didn't get into that "skinny space" between the Impy and wear ring to start a scoring or galling process . If a guy is going to "break in a cam" for example depending on the condition of the jet chances are there could be some isssues ,don't loose sight of the fact that the impeller will "grow" slightly as rpms increase ( buzzing the motor) so a guy "rapping" the motor on the trailer runs the significant risk of some potential problems . My opinion is still to play it safe ,disconnect the driveline just my 02 Tom

My jet has a hose fitting in the supply line from pump to motor. I connect the water hose and get water flow both ways, through motor and out exhaust and through and out the Dominator jet.

Is this not enough to protect the jet internals for short test runs?

 

[jetboatperformance]

My jet has a hose fitting in the supply line from pump to motor. I connect the water hose and get water flow both ways, through motor and out exhaust and through and out the Dominator jet.

Is this not enough to protect the jet internals for short test runs?

Honestly no IMO you still run the risk of Impeller/wear ring damage .... Tom

 

[92 cole]

My jet has a hose fitting in the supply line from pump to motor. I connect the water hose and get water flow both ways, through motor and out exhaust and through and out the Dominator jet.

Is this not enough to protect the jet internals for short test runs?

To add to Tom@JBP response. Let us not forget about the stern end of the pump shaft. Water lube only and if a sealed unit-remember the heat that will happen out of water and the grease will heat up in a heart beat. Short test fire-ups should not be a MAJOR problem, but you have to define "short". Remember it is a propulsion unit designed to run in water, If you take a fish out of water for to long what happens?

 

[farmo83]

Other then to light it off to see if it will start, mine is never run out of water. I have known plenty of people to do so and they still seem to get along just fine.

 

[oldmxdog61u]

newbie here. I have been looking at threads with this question for the last few weeks trying to get some concensus (ha) on this subject and I guess I cannot, so I figure if a pump guy (Tom) tells me "bad" then I will limit my dry fire to when I pull the boat out of the water and I fire it up for 2-3 second to blow some water out of my logs. No more tune it with the hose jacked into the pump and the driveline connected like the prior owner said was fine and as seen in many other threadrs elsewhere :-0

Thanks for the wisdom here.

 

[RiverDave]

newbie here. I have been looking at threads with this question for the last few weeks trying to get some concensus (ha) on this subject and I guess I cannot, so I figure if a pump guy (Tom) tells me "bad" then I will limit my dry fire to when I pull the boat out of the water and I fire it up for 2-3 second to blow some water out of my logs. No more tune it with the hose jacked into the pump and the driveline connected like the prior owner said was fine and as seen in many other threadrs elsewhere :-0

Thanks for the wisdom here.

Welcome to the board..

RD

 

[Flat Broke]

My jet has a hose fitting in the supply line from pump to motor. I connect the water hose and get water flow both ways, through motor and out exhaust and through and out the Dominator jet.

Is this not enough to protect the jet internals for short test runs?

The first problem with this idea is that the water will be entering the pump behind the wear ring, and there is nowhere near enough volume to ensure that water gets between the impeller and wear ring in this fashion.

The next problem, as was previously stated, is that the water certainly won't be adequte to cool the rear bushing, and in the instance of a water lubed bowl, will be completely inadequate for lubrication.

Last but not least, when the impeller isn't loaded with water, the entire assembly is far more likely to demonstrate some degree of deflection which would allow the impeller to contact the wear ring and erode the relatively tight tolerances you would hope to have there.

So yeah, if you want to bump it to see if it will light, that's about as far as I would go without disconnecting the driveline or making sure the pump was submerged.

Chris

 

[oldmxdog61u]

amazing how hot those log to transom rubber hose connectors get if you dont have water in there. Doh!:bowdown:

 

[jetboatperformance]

amazing how hot those log to transom rubber hose connectors get if you dont have water in there. Doh!:bowdown:

And to add to that though all you folks with thru hull systems whether the be Jets or otherwize would do well to inspect your rubber hoses between you tips and rizers with some regularity Poor or inadequate water flow will/can cause them to "Blister" and delaminate internally , they may "look" fine from the out side but a glance up thru the tip will give a good idea as to the health of the connector hose . a blown exaust hose is a quick trip to the bottom Tom

 

[Abc123]

Great advice by Tom!

Also, while pulling a boat to the river a ton of crap gets sucked into the pump like a vacuum on the highway. Not a good a idea to fire it up out of the water with all that junk in there. When I get up there, The 1st time I launch I back in, pull it out real quick then back it down to kinda wash all the junk outta the pump before starting it.