Changed Drive Shaft ???????? - Page 7

Burty · 10-03-2007, 07:32 PM

Choppers are a bow lifting prop, Cleavers are Stern lifting

RossM · 10-03-2007, 07:36 PM

Quote:

Originally Posted by Peterjfinch

"Over the hub props create slip, massive slip in the low RPM range 4500 and lower.

Peter

Yes an over hub prop will slip when your getting on plane, but once your up its fine.

Quote:

Originally Posted by Peterjfinch

"
You do not have a HIGH RPM engine.
The over the hub prop will not make use of the torque your engine has.
Only making use of 1500-2000 rpm

Not true

Quote:

Originally Posted by Peterjfinch

"
If all you want is top end, and not caring weight give one a try.

True, kinda.... a chopper is a bow lifting prop which is used for high speed, but you need more bowlift to get the boat to run right!

make yourself some setback with a few bits of wood, make about 2" of setback, then put it between the engine and transom....then see how it goes.

Peterjfinch · 10-03-2007, 07:47 PM

Thanks Puppy, That's a good idea. I'm gonna run some more tests next week, will make them up and try that also. At least it will give a good idea.

I've drained the belly tank (over 80 ltrs) and will use a 30 ltr tank behind the back seat, to try it.

I'll post the results as they happen.

Thanks

Peter

RossM · 12-03-2007, 02:02 AM

o.k then dude, keep us posted.
try to get some vids as well.
any weight you can shift back or remove from forward part of the boat will help! even try removing the passenger seat and kick board as there only 4 bolts each and weigh a few kgs.

RossM · 14-03-2007, 02:01 PM

here ya go dude
http://cgi.ebay.com/ebaymotors/T-H-M...em320011319388

Peterjfinch · 15-03-2007, 11:12 PM

More trials tomorrow, weather permitting. Belly tank drained (about 90ltrs)

I've got two 25kg bags of salt tablets, that will go either side, low down under the splash well. I've got a plastic container for fuel, about 40ltr, that will be roped to the rear seat, central. I will try it with them and do a couple of runs, in each direction, checking max speed and revs after each. Then I'll move the fuel to one side and take the salt out from that side. After a couple of runs like that, I'll take the other salt bag out and put fuel (what's left of it) back in the center and do a couple more. All these runs will be without the forward weight of the fuel, in the belly tank.

All this will be on video, so those who know, please be ready to give your opinions.

Peterjfinch · 17-03-2007, 08:49 AM

OK, Videos uploaded. Sorry about the camera person, I couldn't drive and video.

Belly tank was drained. A 40 litre fuel container, strapped to the rear crossmember.

Pass # 1... As above. 54.3MPH.

http://www.youtube.com/watch?v=KMm2hzoQP9M

Pass # 2 + 3...As above plus 25kg under splash well. 54.2MPH.

http://www.youtube.com/watch?v=Mqx_ILzVv9o

and

http://www.youtube.com/watch?v=dd0k3Yj23Q8

Pass # 4, 5 + 6... As above plus 50kg under splash well. 53.7MPH.

http://www.youtube.com/watch?v=mIakt4vesdc

and

http://www.youtube.com/watch?v=gAikpBjGiGY

and

http://www.youtube.com/watch?v=UEbtoxijhNY

All reved around 5700 RPM. Didn't trim out as much as the last test runs. Water pressure stayed up. No warnings.

What's your opinion?

Peter

Burty · 17-03-2007, 11:45 AM

i'd say thats pretty good. Bow is out pretty well. not sure why the speed is so low though. you should be doing 60+ recon if you removed the flag you would speed up a bit though

Peterjfinch · 17-03-2007, 10:44 PM

Hi Burty,

Do you honestly think the flag would cause such a reduction in speed? Is there anything else you can think of, It's been suggested that, being an ex government engine, it may be timed slightly retarded.

Any other ideas, anyone. ?????????

The Docta · 18-03-2007, 10:10 AM

Still looks like your running with a little rooster to me - try trimming in even further?

Looks like its running nice and level though.

Peterjfinch · 18-03-2007, 10:40 AM

Hi Docta,

As you can see from the video, I trimmed out as far as needed to stop the porpoiseing, under that amount of trim, it wouldn't stop.

I'm in the UK in about a weeks time, only for a week. I'll be picking up a set of trim tabs and the bow tank pick up and control. Maybe after getting them set up, it may be easier to stop her porpoiseing.

Also got a 23" Yamaha prop, on its way from the states, that may also help.

Keep the ideas coming, Please.

Peter

Burty · 18-03-2007, 02:32 PM

It has been said by lots of people that you do not need tabs on a P21.
I don't know of any that run with them.
It was a joke about the flag but i'd expect it to make a slight difference. don't know about the engine timing being retarded but a prop can make 5MPH difference

Burty · 18-03-2007, 02:35 PM

Plus why do you want tabs?? they will just keep the Bow down which you don't need and stop the boat rolling onto its side which you say you have sorted. I run tabs but only because the P20 has a tendancy to list in the wind and certain sea conditions, but the P21 doesn't suffer from this!!!

Peterjfinch · 18-03-2007, 04:37 PM

Hi Burty,

I'm putting tabs on so that I can keep the speed down a bit, when towing my son. He's brave but not that brave.

Also, I'm hoping that the new prop will give more bow lift, that may need calming a bit when running slower.

I may have just found the few MPH that's missing. The first picture below is with the throttle arm at max movement. The second picture is me holding the carb linkage on full. Do you think this could be the problem???

Peter

Burty · 18-03-2007, 05:28 PM

best way to check is to remove air box and look at the carb butterflies they should be fully horizontal at full throttle

Peterjfinch · 18-03-2007, 05:44 PM

Hi Burty,

Took air box off earlier and NO, they were not. I done the following procedure and now they are closed at no throttle and fully open at WOT, with .25mm clearence between shutters and stop.

CARBURETOR SYNCHRONIZATION
1. Loosen 3 carburetor synchronization screws to allow shutter plates to close completely.
2. Position throttle lever so that idle stop screw is against idle stop and move roller arm
until roller lightly touches throttle cam. Adjust idle stop screw on throttle arm to align
mark on throttle cam with center of roller. Without moving roller from this position, retighten
carburetor synchronization screws.

Will I now have to adjust the idle speed? I'm gonna try to set up the timing etc, when I get back from the UK.

Peter

Burty · 18-03-2007, 05:50 PM

Quote:

Originally Posted by Peterjfinch

Will I now have to adjust the idle speed? I'm gonna try to set up the timing etc, when I get back from the UK.

Peter

Yes you probably will, shame you couldnt just adjust the throttle stop without adjusting the butterflies individually. i'd run it on the hose and check the idle before taking it out again

Peterjfinch · 18-03-2007, 07:20 PM

Hi Burty,

Have been reading through the entire synchronization and timing setup. I think I'll be better of setting it up from scratch, when I get back. Do you think the gap on the carb linkages would have caused the loss of power?

Following the manual, the procedure is not a 5 minute job.

Peter

Burty · 18-03-2007, 07:53 PM

If you wern't getting full throttle then yes you would notice a speed increase

Peterjfinch · 05-04-2007, 05:25 PM

Hi all, back in Mallorca. Just spoke with Bobs machine tech, not sure if this will be of any use to anyone but, he said that although the point of the nose cone should be in line with the centre of the prop shaft, it would be ok if it was around 1/8" below but not above, as above would cause stern lift.

Prop is in the capital here, in customs. Will pick it up next week.

Hopefully my next postings will be the next trial run.

Thanks all.

Peter