Dhadley, and all, Set-up . Rpm Results and Questions

[KYHunter2]

I ran my boat yesterday, finally.

I raised the motor one hole as instructed .

I can't believe the difference , its like a new boat.
I can get 5600 rpm's at WOT. But at about 5400 there is starting to be some steering torque to the stbd. side.

The sweet spot is around 5400.

I never did trim it enough to blow out , but I'm sure I can ,as there is trim left.

The hole shot is still very good. I have a hydrofoil on it , and wanted to know if I need to take it off.

The old owner didnt have it on. I installed it to get on plane faster. But I think it was due to a weak ,motor not need for it.

My gps speed was 51 mph at 5500 rpms .

Whats next ??

Do I need to go to a 17p prop. The one on it is a 19.

The boat is a 15'6 procraft bass boat.

Also what is an average load exactly ?

I have 3 batteries , (during test run , I had 10 gal gas.) Probably 150lbs. of gear , and my 200lb butt.

Does it sound like Im OK ?

Or do I need to get the other 2-4 hundred rpm's.

Or do I have more then a average load ?

Thanks ,

KYHunter d

 

[ob]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

Can't comment on the engine rpm range without knowing what engine is in question.As far as the steering torch at 5400 rpm,there is a trim tab on the lower unit that needs to be adjusted in the direction of the pull and then water tested to fine tune.I would determine whether you are going to retain the hydro-foil though before making the final adjustment.

 

[deejaycee_2000]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

Leave the hydrofoil it won't decrease your speed, go with a stainless steel 17' prop ... you will fly like the wind

 

[steelespike]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

If your getting 5600 rpm at WOT I don't think you should drop to a 17 in. prop.I've had good luck with foils but they should be considered a last resort after careful trimming of motor and weight.If you feel you still need some help give the smart tabs some thought they are a world better than the foil.If you are lucky you may get one more hole without blow out trouble.Give it a try the worse that will happen is you go back.Just be sure it pumps water.Be sure to remove the foil until you get the final trimming all set.When refering to average load they mean what is your average load.(typical load)Roughly speaking you were at about 550 lbs on your test run.
My guess that is about 1/2 the rating of the boat.

 

[KYHunter2]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

Sorry about not posting the engine.

I had all the info. in a earlier post .

The engine is a 115 johnson / evin. 1978 .

Actually it is a motor I rebuilt from bottom up . It has a bored evinrude block . 020 , new pistons , rings . etc. everything except con-rods.

I've put around 30 hours on since breakin.

I'll try adjusting the trim tab .

OB, do you mean if I have torque to the right , I move the tab to the right ?

The reason the foil is on is as I said before rebuild , I had trouble getting on plane.

I doubt I'd have any trouble now without it. I plan to remove it and try it out.

The plate on my boat says 1000 lbs. gear/ motor / persons. Max .

Thanks,

KYHunter

 

[ob]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

That's correct.The rear or fin of the trim tab ,should be adjusted toward the direction of the pull to correct torque steer.You'll want to run the engine at or near WOT with it trimmed out to see if torque steer is present.Many adjusted correctly will tend to pull a bit at slower to mid speed and settle out at higher speeds once the prop is pushing the most water through the tab.

 

[KYHunter2]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

When I get it to what I call the sweet spot. ( no torque either way ) It is at roughly 5300-5350 rpms.

After that the torque starts and kind of builds , up to , my present WOT rpms , 5500-5600.

Its not , by any means , hard to control. But, enough to pull to the right.

When you mentioned , pushing the most water.

I'm wondering , could the way the foil works cause torque ?

I know the foil is out of the water at WOT, but it still seems to deflect the water.

Thanks,

KYHunter

One thing I just noticed , I have a habit of hitting the question mark a few times. Now I see why my other posts have a emoticon with its mouth like this O. LOL . no more 3 Q Marks.

 

[ob]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

When you mentioned , pushing the most water.

I'm wondering , could the way the foil works cause torque ?

Thanks,

KYHunter.

Absolutely.Anything that influences the flow of water aft can effect handling or boat posture.

 

[KYHunter2]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

ob,
Thanks alot for the help.

I'm going to try it minus the foil , then if necessary . Adjust the trim tab.

KYHunter d

 

[moderator1]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

I'd consider going up another hole as well..providing the engine is in the second hole from the top now...
should gain another 75-100RPM, and the third hole, in most cases, won't negate water pressure.

 

[phatmanmike]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

lose the foil. its just adding drag

 

[Texasmark]

Re: Dhadley, and all, Set-up . Rpm Results and Questions

If you want a better hole why not port your prop (drill holes in the side; one per blade). Any reputable prop shop can do it for you. Porting forces prop cavitation/ventilation at the lower rpm's that allow your engine to develop it's rpms rather than lug under the load. This results in much faster hp development which turns the prop harder/faster and planes out faster. Once up to speed, the flowing water (by the holes) seales them off and you don't know you have them.

Mark