prop and pipe questions

[Rick Sowell]

couple of questions for the more experienced boaters. the boat is a Bob Tuttle sport 20, Mac 21, AB parabolic, prop is 40/53. I have been having problems with losing speed the longer it runs, will run like stink for about half of a heat and then lose power, tried richen and lean on the needle and it doesn't get better. I think I might have the pipe too long, it's at 8 1/2 right now, have tried to shorten and lengthen still doesn't seem to get much better.fuel tanks are good, all new no change, new BV needle, bearings are good, no air leaks, plug doesn't show lean. The big question I have is the relationship with pipe length and prop pitch, If I shorten the pipe more will I lose the ability to run this prop? shorter pipe bigger prop? or shorter pipe smaller prop?

 

[shoboat]

Rick,

Wrong propeller, try a 1614/3 chopper, that is what Bob used to run.

Shorter pipe less cup that the boat will pull. FYI, ABC 40 x 53 has

a lot of cup in the T.E. stock. Reduce cup and it will run better.

Pipe should be about 8".

Have Fun Testing,

Mark Sholund

 

[Rick Sowell]

thanks Mark for the reply, do you have those props in stock and how much? I tried one of your M440 props and had similar results, I tried a different pipe a OPS 3280 and it made the boat much better, I was just wanting to know why this pipe and prop combo that used to work now loses speed after a few laps. the boat is pretty heavy so I need the pitch to get any speed out of it. thanks Rick

 

[LarryConrad]

thanks Mark for the reply, do you have those props in stock and how much? I tried one of your M440 props and had similar results, I tried a different pipe a OPS 3280 and it made the boat much better, I was just wanting to know why this pipe and prop combo that used to work now loses speed after a few laps. the boat is pretty heavy so I need the pitch to get any speed out of it. thanks Rick

What shape is your engine in? You might be losing compression as the engine heats up. I had the same problem with the Mac 45 in my Eagle after it got over heated with a plugged water pickup. It would go like a bat out of he** for 2 laps and fall flat on its face.

 

[Rick Sowell]

Larry: I have checked the temp as soon as I get it to the beach and if anything it is too cool, warm but not overly hot, I have even restricted the water going to it to get more heat in the motor, motor has good pinch at top, so it is in good shape.

as stated in the above post I tried a OPS pipe and it didn't do the same thing with that pipe, it ran great for the whole tank, looks like I will have to stay with that pipe for now. just curious as to why the other pipe decided to not work any more no matter where I have it set in length. maybe there is something wrong with the internals of that pipe.

 

[shoboat]

Rick,

Have you ever cleaned your pipes?

The 3280 is a better pipe.

Thanks,

Mark Sholund

 

[LarryConrad]

Larry: I have checked the temp as soon as I get it to the beach and if anything it is too cool, warm but not overly hot, I have even restricted the water going to it to get more heat in the motor, motor has good pinch at top, so it is in good shape.

as stated in the above post I tried a OPS pipe and it didn't do the same thing with that pipe, it ran great for the whole tank, looks like I will have to stay with that pipe for now. just curious as to why the other pipe decided to not work any more no matter where I have it set in length. maybe there is something wrong with the internals of that pipe.

Rick,

I have the last version of the boat that Bob built,I believe he made five different designs. Should finally hit the water with it next week. He told me he ran his with a long Parabolic and a Prather 215, and also a 1614 as Mark suggested. The only .21 Parabolics I have any experience with are the long and the fat. Both work very well on my Valvola in a Speedmaster mono The OPS 3280 is one of the best 21 pipes available, though my experience with them has only been on Novarossi engines. The 45 Mac I mentioned had lots of compression...When it was cold. 2 laps and you could spin the motor over turning the prop by hand with the plug in.

 

[Rick Sowell]

Larry: I have the M&M's boat that Bob had in his avitar, boat runs well and handles the rough water like a dream, just a little heavy for my tastes. been trying to get more speed out of it to maintain my position in the dist. points race. what length are you running your parabolic at? I have ran mine at 8-8 1/2 and it just loses speed after a few laps.the boat used to run great and then with no changes it went to running like a turd, can't figure it out. I have been playing with my new flow meter from Boris and noticed that the BV needle that I had that was mounted on the carb didn't have a very sensitive range, checked it against a OS needle and the sensitivity is very noticeable. I have changed needles and hope this will be the fix for the problem, we will see on Saturday at the race. Rick

 

[LarryConrad]

Larry: I have the M&M's boat that Bob had in his avitar, boat runs well and handles the rough water like a dream, just a little heavy for my tastes. been trying to get more speed out of it to maintain my position in the dist. points race. what length are you running your parabolic at? I have ran mine at 8-8 1/2 and it just loses speed after a few laps.the boat used to run great and then with no changes it went to running like a turd, can't figure it out. I have been playing with my new flow meter from Boris and noticed that the BV needle that I had that was mounted on the carb didn't have a very sensitive range, checked it against a OS needle and the sensitivity is very noticeable. I have changed needles and hope this will be the fix for the problem, we will see on Saturday at the race. Rick

Rick,

I was running the long parabolic on my valvola at 8". I am now running a fat parabolic at 7 7/8". As soon as I finish painting my cowl I'll have my Tuttle sport 20 in the water...early next week, Mac 21/long parabolic/ prather 215 to start with. I'll have to weigh mine after I add weight to balance it, right now it's lighter than my PT SS21. How do the tuttle boats turn with the straight turn fin?

Larry

 

[Rick Sowell]

Larry: my boat turns great with a straight fin, the fin has a curved leading edge sort of a semi circle shape, hope you like yours, there is another one in our club and it runs great as well, good boats too bad Bob quit building and racing.

 

[LarryConrad]

Bob sure did build some nice boats, I'm looking forward to running it.