Motor flusher question

[TownsendsFJR1300]

And that Skeg guard, if you were to putty and smooth out the crevices and bumps you will get improvement. This will spoil the look though. But I suspect where the extra drag comes from can't be much improved, and that is at the guard's trailing edge. It has a dubious airofoil section (chord) not in harmony/compatible with the speed it travels at.

The stock skeg, is probably 1/3 the thickness of the Skeg Gard, hence, a bit more drag.

It should be noted that it fits like a glove (had it custom made with the drain at the left side, rear-it's usually up front).

For 1 MPH (at WOT), to protect the skeg, (keep me from re-painting every time I run aground, additional protection for the prop), is IMO, well worth the cost, installation, etc..


BTW, the bolts that secure it are designed to shear off if something hard enough is hit vs ripping your LU apart..

[panasonic]

Water pickups effectiveness is quite an aerodynamic science - requires the equivalent of wind tunnel testing. Often what you think happens does not. Eg. The leading edge of an airfoil like the outboard leg is not where the maximum pressure is.
I have had first hand experience with Radio Control boat cooling systems, none of which seem to be employed in full sized boats.
The pickups: there are basically three. One uses the rear under hull pressure. Second uses a hole in the side of the rudder similar to Townsend description photo.
And the third is simply a vertical tube with the end cut off at 45 degrees facing the flow of water. This one is where it is interesting. If you were to have bent this tube 90degrees with the end opening fully facing the flow of water (as seen on small outboards) the efficiency of this arrangement is abismal. The 45degree version is many times more effective! It has all to do about the turbulence, drag call it aerodynamics, at that opening!

A lot more to it then we know....

[zenoahphobic]

The stock skeg, is probably 1/3 the thickness of the Skeg Gard, hence, a bit more drag.

It should be noted that it fits like a glove (had it custom made with the drain at the left side, rear-it's usually up front).

For 1 MPH (at WOT), to protect the skeg, (keep me from re-paining every time I run aground, additional protection for the prop), is IMO, well worth the cost, installation, etc..


BTW, the bolts that secure it are designed to shear off if something hard enough is hit vs ripping your LU apart..

It's a balance between pros and cons. I myself look after my original skeg, but have thought about putting a guard on but at this point decided against. There is the loss of top speed that is not so important, but that drag will use more fuel at a broader range of speeds.
There was also the question of upsetting stresses on the leg. Firstly, if I hit something hard the skeg might survive, albeit severed and sunk unrecoverable, the damage perhaps far greater on the gear case, and the propeller! than if it were just the original alloy snapping, The original skeg can partially snap that can be built up again without the need to strip the gear case out. But also the vibration fatigue that may fracture the skeg over time, because of the added mass.
Of lesser relevance perhaps, the new "3 times thicker" thing is directly in the water flow preceding the propeller ; the changed turbulence must have some effect on the performance of the propeller. You may even reduce the drag of the skeg!, but have lost the gain by turbulence at the prop blade!
If I was to have one made, there was the opportunity to measure the drag; even replicate the existing skeg for drag comparisons.
All of this is academic discussion, and not meant to be anal obsession about " to have or not to have".

[TownsendsFJR1300]

The only difference noticed is the top end, which is minimal... (White knuckle ride over 40 MPH anyway)...

As noted earlier, the securing bolts are designed to shear away.

As you can see, where it bolts the LU, is pretty meaty.

For some boating in "rocky conditions", this may or may not be the best option.

Down here, in the river, before I get out to the Gulf of Mexico, is mostly sand and oyster bars. No large rocks to take out a LU..