Engine under load???

[hockeyfan55]

Is a motor under the same load if it is just in a barrel of water compare to when the whole boat is in the water??

I had a motor last summer that had no power under load but ran nice with muffs on it

 

[Home Cookin']

Re: Engine under load???

no.

 

[hockeyfan55]

Re: Engine under load???

what is the difference? do you suggest only buying a motor if you see get to see it pushing a boat in water?

 

[glengold]

Re: Engine under load???

Several differences, mainly you can check WOT. A motor on muffs is not under load!! You can't compare a motor reving up in neutral to a motor reving up while pushing a boat (under load). Running on muffs creates no back pressure from the motor being submerged. To run WOT in a barrel you need a test wheel (prop). Google it.

That being said I've bought a motor without testing it on a boat. test compression. check LU lube.

 

[glengold]

Re: Engine under load???

I should add u don't want to rev up on muffs anyways!!

 

[hockeyfan55]

Re: Engine under load???

so putting the motor in gear while it is submerged in a barrel is not under load? which starts another problem because you cannot test WOT in a barrel because it will just thrown the water out and have no pressure again. so a barrel and muffs are pretty much the same, you wanna get the motor on the water?

 

[444]

Re: Engine under load???

Well if you put it in a barrel you can't put much load on the prop before spraying all the water out of the barrel. Tried that with my mercury 90hp, blipped the throttle a little too hard in the barrel and threw 10 gallons of water all over myself. Really the only way is to get the motor in the water. If that's not practical then you do a compression check, lower unit oil check and take your chances.

 

[QC]

Re: Engine under load???

I see three questions:

1) Load on muffs? Equal to damn close to zero.

2) Load in barrel? How bigga barrel? Significantly more than muffs, but depends on ability to seriously mover the water with out evacuating all of it. Maybe a better way to ask is what load in an Olympic size pool with motor attached to a bracket on the side? Full load and deep lug concern. Same as tying a boat to the dock and mashing it.

3) Load on a boat? Well, we all know that.

 

[Home Cookin']

Re: Engine under load???

I saw a home made test tank that basically covered the barrel so the water wouldn't splash out. I still don't think it would give you the pressure, especially with all the air. Still you don't put the force of pushing a boat against the engine.

On muffs or a tank, you can put it in gear in idle and listen for clunks, feel how firmly it shifts, etc. That's all you need to do to test one, and compression.

If you did run it up to WOT, what would you learn? the RPMs would be off with no load; may as well run it up in neutral BUT DON'T!

I read here about the consequences of running a motor up in neutral or with no load--it can take off and keep running until it flies apart literally--a big ol OMC grenade.

If your motor isn't giving you power under load it is likely starved for fuel, but there could be other problems as well, like bad compression.

Typically, anyone buying just a motor isn't going to be able to test it on a boat. A big motor is too much trouble to rig; a small one isn't worth the bother. A "poor man's boat yard" here sells old motors of all sizes with a 30 day return policy; I'd think other dealers would do the same. But not the typical private seller.

 

[Frank Acampora]

Re: Engine under load???

When you rev-up and engine in gear in a barrel, the water is churned, entraining air, and exhaust also mixes with it, reducing the prop's "bite." Load is very much reduced unless you have a special test tank or test wheel (not a prop).

I have seen marinas that attach a positive displacement pump to the prop shaft and run the engine like that--something like being on a dynamometer because the pump provides the correct load on the propshaft.