SAW prop

[Gary]

I have a 30 inch hydro that has gone 70 mph on a M645 prop but it seems to drag the transom alot untill its on plane. If it does not get up it will run 63-65 mph. Will a 3 blade give me added lift or should i stay where im at? I was thinking of a 1742 3blade with 1.7 pitch in it. The motor is a NEU 1521 1.5 D on 22 volts and boat comes in a 6.8 lbs. What do you guys think?

[Ub Hauled]

change the angle of the strut a hair or the CG a bit... keep the prop and make sure you are not happy with it.
Usually Hydro SAW props as 3 blades, but not exclusively.

[Fluid]

Put the boat on a flat surface resting on the sponsons and the strut. Add 1-2 degrees of down angle at the prop end to lift the transom, but be careful. Too much and the transom may hop - this is for the prop you have. Lifting props probaby won't need any down angle.

70 mph is about right for that setup, it depends on the hull. Some will run faster with the same setup, some slower.

You may not like the 1742/3, it has no more pitch than what you are running but a lot more lift. It can be tough to get on plane too. Try a v942/3, it has less lift than the 1742/3 but more pitch. Be careful with SAW setups, don't run for more than two passes. BTW, how long is your straightaway?



.

[Gary]

I will send it out about 75-100 yards and slowly go to full throttle. If this was your boat would you waste time with another prop? I hate the learnig curve of a big change. It just seems sometimes the boat flys and other times it does not get up out of the water.......i mean 64 is fast but at 70 it screams and i know when its on a good run from the motor pitch. Another thing is this seems to happen,runs faster, when the boat hits a little turbulance in the water and it forces itself up higher .....mabe im wrong.

[Gary]

Fluid ...is it worth while to take out the teflon liner in the stuffing tube? I tried it one time but didnt get a gps reading and it made a mess with the grease as well.

[Fluid]

If you remove the teflon you must replace the brass tubing with the next smaller size. Otherwise there is too much radial space for both thrust transfer and cable windup - not to mention the greasy emulsion.

Your description tells me that the boat is probably too stuck down on the water...for the highest speeds anyway. It is probably safer from blowoff though. Have you wet-sanded the sponsons to true them up? My Larsony had concave sponsons bottoms. How deep are you running the strut measured from the bottom of the hull to the bottom of the strut?


.

[Gary]

It is 1/2 inch from bottom of boat to bottom of strut with 1 degree down angle like you said. The boat seems to plant the right sponson down on a 63-65 mph run like its twisting to the side. This boat comes in at almost 7 pounds. Is that to heavy?

[Fluid]

I ran between 7/8" and 1-1/8" deep on mine, depending on the prop and setup. You're too shallow, that's why the transom is dragging. I had to bias my packs to the left side to keep the sponson from digging in. Seven pounds is not light, but then my 4S Sport Hydro weighs almost 10 and it runs ~60 in oval trim. You need enough weight to keep the boat on the water.




l

[Gary]

Ok i am going to shift some weight around and lower the prop a little more and see what happens. Before my batts died today i tried the prop more shallow to see what would happen and it was real squirly all the time and only ran 60 mph so you must be right........... I had marked my prop setting and never moved it because i figured it made that 70 mph run a few times so it should do it every time but i guess not...must have been luck. Like i said though she will go 64-65 all day. I also found she runs faster against the wind but will blow over most of the time so it must be the extra air lifting it up. BTW what combination did /do you run..motor, props? Thanks for your time.

[Fluid]

I ran the Larsony on an 8XL with 12 very good NiMH cells, and usually an x440 or x442 prop for oval racing. For straightaway I ran an m645. The deeper the strut the less likely to blow off, but run it too deep and the front of the sponosns will dig in.....


.

[Gary]

So how fast was your m645 prop setup? Was there work done to it.... i cut mine down a little smaller and sharpend it to a razor.

[Fluid]

Actually I set up the boat for drag racing with the 7XL and m645. It launched very hard and IIRC it hit about 62 mph on radar after 165 feet from a dead stop.

For oval running that would probably be too much prop. The Larsony likes to lift the left sponson from prop torque with an x440.....


.