Running boat on land with no prop?

[newtoboat101]

Hello all, have a 5.7 vortex new engine /alpha 1 gen 1 question is can I run an outdrive in a tub with no prop just to check shifting into and out of gear right now I have outdrive in 125 gallon tub ,boat on trailer when i put in gear it propels boat forward so can i run with no prop in tub .I prefer running in a tub instead of muffs ,i do change water when it gets to warm. About a 30 minute runtime,if I deflect exiting water I get about 50 minutes run time

 

[JASinIL2006]

No, you cannot run in a tub (unless you have a tub that allows most of the outdrive to be submerged). The water pump on an Alpha won't suck water up out the tub; with muffs, you have the water pressure from the hose forcing water into the pump and up into the engine.

Running the engine as you propose is a bad idea.

 

[Rick Stephens]

What he said.

 

[Rick Stephens]

Would add that you pretty much can’t test shifting beyond what you do on muff without loading the prop in the water. Most of the shift system is designed to accommodate always being under a load. Shifting out of gear is the difficult part when the entire drive train is always loaded.

 

[Scott Danforth]

raw water pumps do not suck/draw.

they only push water.

to push water, you need either 8" of water over the pump (such as the boat in the water and the drive would be submerged), or you need a garden hose forcing water to the pump (such as muffs)

running in a tub simply cooks your impeller and if you have the plastic pump housing, it melts that.

 

[Bondo]

Ayuh,..... Or,.... You could run it on muffs for hours if ya want,.....

Probably somewhat safer, with muffs on, prop off,.....

 

[newtoboat101]

This is my setup and shower top of outdrive to cool you think muffs are safer

 

[Scott Danforth]

This is my setup and shower top of outdrive to cool you think muffs are safer
View attachment 370118

So how do you get the static water level 8" above the impeller with your setup?

Answer - you can't. Yes, muffs are better and safer

 

[newtoboat101]

ok, not trying to battle you ,i understand that muffs force water up into outdrive and thats better ,when ever i use muffs ther seem to always be gaps in muffs to outdrive it seems i get less water exit water,,and temp runs higher ,than with the tub seems more stable ,but yes its maybe only 3-4 inches over opening in outdrive ,but totally understand your justification for muffs thanx for your help

 

[Scott Danforth]

Water inlet is 3-4" below the impeller. You need water 11-12" above the inlets

 

[Bondo]

Ayuh,.... The water has to be over the trim rams, Atleast,....

 

[Scott06]

ok, not trying to battle you ,i understand that muffs force water up into outdrive and thats better ,when ever i use muffs ther seem to always be gaps in muffs to outdrive it seems i get less water exit water,,and temp runs higher ,than with the tub seems more stable ,but yes its maybe only 3-4 inches over opening in outdrive ,but totally understand your justification for muffs thanx for your help

This probably says more about the muffs you are using than muffs vs a tub. As others have pointed out u want to ensure your tub has the drive well covered in the water you are probably 6-8 more water above what you have pictured here

 

[jimmbo]

The guy's mind is Made Up. Don't confuse it with Facts.

 

[muc]

Wow, over 30 years as a marine mechanic/technician. Almost 20 years as a MerCruiser Master Tech. Attended every factory class they had. Never heard the instructors say that the water level needed to be any higher then the anti-ventilation plate. Ran 100s of I/Os in test tanks. Where are you guys getting this info?

O.P.
Yes you can check shifting with the prop off. Just about every manual recommends to remove the prop when running the engine out of the water for safety reasons. Note that this won't check the shift interrupt system, there needs to be a load on the clutch dog to check that.

Pro tip to check shift adjustment out of the water.
Engine off,
shift into forward and try to spin the prop. Should lock in one direction and make a ratcheting noise in the other direction. Now do the same in reverse, same results but in a different direction. Should ratchet slightly easier in reverse then forward.

 

[jimmbo]

AV plate is below the Pump, and the pumps work much better if Primed, which means submersion

 

[muc]

Facts from the Johnson pump marine catalog.

The primary advantage of a flexible impeller pump is its self-priming ability. As the vanes of the impeller are depressed and rebound, they create their own vacuum drawing fluid into the pump. A dry pump can lift water up to as much as 3 meters. Thus a flexible impeller pump being used for engine cooling needs not be located below the water line or manually primed.

O.P. one of these is easier and just as safe as a tub.

I'm just asking all the people who posted this "can't lift water"
8"
11-12" above the inlets
water has to be over the trim rams
Where does this come from?

You can't get the water level above the trim rams in a test tank, yet MerCruiser uses test tanks at their factory schools?
I'm just asking the posters who jumped on this. Where did you get these "facts"?

 

[Rick Stephens]

I don’t know how high you need to be, but Alpha pumps are vented to self prime when submerged. they don’t lift worth a damn. I don’t have thirty years working on em though, so happy to accept contrary opinions.

 

[topgun3690]

"Pro tip to check shift adjustment out of the water." Good information right there.....

 

[muc]

I don’t know how high you need to be, but Alpha pumps are vented to self prime when submerged. they don’t lift worth a damn. I don’t have thirty years working on em though, so happy to accept contrary opinions.

That little hole isn’t for venting/primping, its on the pressure side of the impeller. It’s there for draining. This is one of the reasons MerCruiser tells you to lower the drive to drain it if the possibility of freezing exists.

 

[muc]

"Pro tip to check shift adjustment out of the water." Good information right there.....

I should mention that this only applies to the MerCruiser “R” thru Alpha 1 gen 2 drives due to the spring loaded shift spool they use. one of the common problems I see with DIY shift adjustments is people put too much pressure on the shift spool causing it to wear out. You should have a fairly light ratchet. People who are inexperienced in MCM shift adjustments should start with the troubleshooting section of the manual before moving to the shift adjustment section.