Prop Testing

[Capt. Crash]

Got the mostly stock boat back out. Tested that cut down (partial de-tongue) 40x52/3 Grim Racer prop this weekend. It was pretty good. I had 10-15mph cross winds to deal with, but never let up on the throttle. The boat was doing the sponson to sponson hop but the water was choppy. I moved the rudder linkage up to the next hole to give me more rudder. I got about 30% more by doing that. I ran my boat full throttle through all the turns and she handled them without a hiccup even with the tighter turn radius. I’m now able to navigate my tight course a lot easier. The new fiberglass modifications are working great and she is rock solid.

I did not get the 46-47mph I was looking for with the prop mods, but got close at 45.5mph. I will leave the prop alone for now and try it again when the conditions are better. The boat ran nice and cool, got on plane pretty easy and had plenty of torque through the turns. :buttrock:

I'm getting 50mph out of the Grim 40x57/3 but it runs too hot to use in the summer for anything more than all out 1 mile run so I want to find the next best thing.

[detox]

Have you tried different strut settings? It looks like your strut is set very shallow or not deep enough. Thanks for posting the cool pics

[Capt. Crash]

I have the prop as far up (shallow) as I can get it....factory setting...about 15/16". I may cut the notch in the bracket some more to get it shallower. I have as little angle as possible too. I want her light on the bow...on the verge of blow over....but not quite. Isn't that when she is fastest? Why would I want the bow down?

She is still running a tad heavy on the bow with this set up and the GPS placed aft.

This is the same place I ran the 40x57/3 and got pretty good runs with her...but she was more stable at 1". She was a tad harder to get hooked up at this setting though.

Enlighten me! :bowdown:

[jingalls007]

I have the prop as far up (shallow) as I can get it....factory setting...about 13/16". I may cut the notch in the bracket some more to get it shallower. I have as little angle as possible too. I want her light on the bow...on the verge of blow over....but not quite. Isn't that when she is fastest? Why would I want the bow down?

She is still running a tad heavy on the bow with this set up and the GPS placed aft.

This is the same place I ran the 40x57/3 and got pretty good runs with her...but she was more stable at 1". She was a tad harder to get hooked up at this setting though.

Enlighten me! :bowdown:

you shouldn't need to cut anything to get the strut down further. are you adjusting the strut where the bracket meets the transom?

[detox]

I may cut the notch in the bracket some more to get it shallower. I have as little angle as possible too. I want her light on the bow...on the verge of blow over....but not quite. Isn't that when she is fastest? Why would I want the bow down?


Being TOO loose is not fast. If boat is real jumpy on sponsons the prop will also jump out of the water making you slower. Keeping the bow down will help keep the prop in the water. I would lower the strut deeper in the water 1 1/8" to make boat run a little tighter or less flighty. Strut angle will also increase slightly when strut is lowered. Just My Opinion...I am no expert.

[TCR]

Being TOO loose is not fast. If boat is real jumpy on sponsons the prop will also jump out of the water making you slower. Keeping the bow down will help keep the prop in the water. I would lower the strut deeper in the water 1 1/8" to make boat run a little tighter or less flighty. Strut angle will also increase slightly when strut is lowered. Just My Opinion...I am no expert.

When you say 1 1/8", from what two points are you measuring? TIA.

[Capt. Crash]

When you say 1 1/8", from what two points are you measuring? TIA.

sponsons and bottom of strut resting flat on table...."measure" bottom of hull to table top at the transom.


I will need to test again in smoother water before I make changes. It was too choppy to see if I was getting prop walk.

[Capt. Crash]

I got the UL-88 Navy out again Saturday. Conditions were ideal for the fast boats. I used the same modified 40X52/3 but lowered it down to 1" after a disappointing first run at around 44.5 mph. I got three long runs at 1 1/2 - 2mi ea. Best time was in my target zone (46-47) at 46.8 mph. She ran great without the sponson to sponson wobble but like I said, the conditions were much better than last time. Temps were very good too. This is a good enough setup to play with for the summer. No turtle kills today although we saw a monster loggerhead stick his head up.

[LuckyDuc]

I'd say that 46.8 is pretty good for the grim 40x52 with the stock motor. I'm getting 48-51mph with that prop on my Medusa 36-60-2200.