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1973 Evinrude 6hp mounting

H

huronpete

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"I just bought my first outboa

"I just bought my first outboard and am confused as to how far in the water it should be. I keep reading about the cavitation plate but I am not sure what that is on this motor. any help would be appreciated. I have ordered a manual, I am just curious."
 
"Still confuses me sometimes!

"Still confuses me sometimes!

Basically the water pump must be submerged at all times.

The water pump is located in the very top of the lower unit (LU) assembly.

Above the propeller there is a horizontal cavitation plate and a couple or inches or so above that there is a joint between the LU and the bottom of the leg if its a standard shaft or the bottom of a 5" tall extension if its a long shaft. The water pump is just inside that joint so if you keep that submerged you wont go far wrong. If you go much deeper than that the pressure on the exhaust outlet may make it difficult to start and inefficient in use.

Also as a rough guide standard shaft models are designed for a transom or bracket height of 15" above the waterline, longshaft models for a height of 20" and extra longshaft models where they exist of 25".

Having said that as an auxiliary on a small sailing vessel it is quite common to mount them deeper than ideal because pitching in a bit of a sea otherwise lifts the propeller out of the water (I use a long shaft 6hp where in theory I should be using a standard shaft for that reason.)

i hope that helps a bit."
 
"The cavitation plate that exi

"The cavitation plate that exists just above the propeller should be approximately 3/4" below the bottom of the boat at the transom/keel, no lower than 1" below."
 
"[i]"The cavitation plate

""The cavitation plate that exists just above the propeller should be approximately 3/4" below the bottom of the boat at the transom/keel, no lower than 1" below"

But in normal trim the bottom of the transom of my boat is about 2" above the water if I mounted the engine like that the cavitation plate would be above the water and the prop would be thrashing air even in calm water let alone in a choppy sea. I think what you suggest may apply to a power boat hull that's designed to plane but not necessarily for other boats.
Surely the water pump must be submerged?

But as I said i have always been confused"
 
"All of the boats that I'v

"All of the boats that I've been associated with since around 1960 to the present that would be outboard powered..... the bottom of the boat at the transom has been flush with the waters surface when underway. I have no knowledge of any boat having a transom whereas the bottom of the boat at the transom would be 2" above the waters surface while underway, and I'm really not interested in being educated of such at my age.

My statement holds and does not pertain to pontoon or sailboats, various tri-hulls as I'm aware that a difference may relate to those type crafts and possibly a few others.

It's best to incorporate the K.I.S.S. system (Keep it simple).... sophistication breeds problems. If the cavitation plate on the higher hp models was placed too low on the transom, a "rooster tail" would be the result when underway..... not a choice factor."
 
""My statement holds and d

""My statement holds and does not pertain to pontoon or sailboats"

That's it I am talking about a small sailing yacht. Fairly normal for the bottom of the transom to be above the water level. Then you can't use that as a guide you have to ensure that the motor is mounted so that the LU is at a suitable depth. As i said earlier it is also common practice to use a long shaft instead of a standard shaft to deliberately put the prop down deep.

The sail versions (I have a yachtwin) are designed with additional exhaust outlets well above the prop, at the bottom of the leg extension and just below a second cavitation plate in fact. I suppose that's the plate which should be just below the water level but I run mine deeper. If the boat is pitching in a bit of a sea and the prop keeps coming out of the water you go nowhere. I had a stanard shft engine at first and swapped to a long shaft for that very reason"
 
"<font size=""-2"">Quote</font

"<font size=""-2"">Quote</font>
"we should be,BOATING"

Couldn't send a truck load of boating weather to the UK could you?
sun.gif
Wet and windy again this weekend!"
 
"we,are in a bad drought here

"we,are in a bad drought here in s central texas,very bad.100 degree days...sweating my a$$ off by 930 am in the shop,but---good boating weather,taking out my searay this wk-end...will think about ya'll."
 
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