Test Tank Gearcase Loading?

[johnyrude200]

Question – I am getting ready to build a large test tank. Can someone explain to me the how the forward motion of the boat puts load on a gearcase (to help evaluate if it is worn, say, to jump out of gear), and how a static position in a large tank (say, 3,000 gallon tank) is not putting a lot of load on the motor.

Is it because when in a static position, the water flow AHEAD of the motor isn’t strong?

I would think that in a test tank you also aren’t creating the same back pressure on the exhaust, unless somehow the motor was set in the middle of a pool on a static fixture.

Thanks

[vintin]

Seems a test tank with a normal prop would put more load on the gear case at all rpm’s than in the water as the motor is not moving forward when in the tank.

[outbdnut2]

In a test tank, the propeller easily cavitates because water can’t fill in in front of the prop as fast as the prop pushes it back, taking load off the prop, and thus sending RPMs up high. There are dummy load props for use in test tanks that handle the water a bit different to maintain a load on the motor.
Some newer test tanks have baffles that get rid of cavitation like the ones in this link:

http://www.specialtymotorsmfg.com/outbo … ttanks.htm

[garry-in-michigan]

Yes – before there were special test props, a standard propeller cut down to get the proper RPM to use for 1000 hour testing of pre production outboards at Evinrude. . . 🙂

[johnyrude200]

All good info. The truth be, I’m acquiring a property with a home-made in ground pool (cement block) that is raised 24" out of the ground, but is 4 feet deep overall. It’s a 5,000 gallon pool I have no use for. I’m converting the entire property to a workshop and am considering utilizing the existing pool as a giant test tank by fitting it up.

Not too worried about water splashback or ventilation issues of the motors since it is outdoors (I have a couple of industrial fans too which are powerful).

Needless to say it’s going to be a lot of work. The big thing for me is loading the gearcase to make sure it doesn’t have any slippage issues. Final calibrations (for motors above 25hp) always occurs on the test boat.

[outbdnut2]

Keep a bottle of liquid dish soap handy to squirt into the pool occasionally to break down the floating grease and oil.
Dave

[vintin]

I’d be worried about creating a mini SuperFund site.

Something like this could be hell to pay when selling the property in the future.

I looked into the possibility of having fuel tanks on my property for a small business and found out the fact that it would be recorded on the property deed. Portable tanks were suggested.

[johnyrude200]

great reference, vintin! Not looking for any EPA or DES flags, still in the planning stages to figure out the best route. I have no plans on moving from this location in the next 30 years (or more). With some elbow grease and patience may be a final stop.

[jeff-register]

VinTin,
I know of a gas station on Rt 66 that did exactly that. Biggest problem was to get the above ground tanks needed to be 500 feet away from the public.
Then again in a one horse town the highway dept wanted to make 4 lanes from 2. They had tanks where the outside lane was to be. The state buried the tanks without cleaning up the site. They are still there 50 years later. All depends on who is doing what eh? Kind like UFO’s, never seen one!

[sydinnj]

Maybe that big, if you make a decked over section so you could mount the motor away from the end and this would give it enough water to pull in and work out ok

[Author]

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