will these two props be about equal?

[FP1201]

The current prop is an "AIR-PROP" 66x34 that's ~8" wide at the widest area and the other is an old Kirkland 66x38 that's ~6" wide at its widest surface.
The idea is the narrower prop with more pitch and less surface will push the same as the wider prop with less pitch.
It's all really a moot point and I won't be able to really test the performance until the re-rigging is finished, but it's fun to conjecture about the anticipated results.

 

[hmgm123]

Man I hope LEO doesn't see this..LOL You have pretty much answer your own question. The only thing that I can add is that one prop will wind up faster than the other prop thus giving you more snap.

 

[Geneva0550]

It should be pretty close. When I had my gpu I ran both a 72x38 stick and a 72x34 paddle and they were about the same rpm. The paddle pushed better but the stick had more snap.

 

[leo_081103]

as geneva said... my bet's on that side --- a case of beer!

 

[FP1201]

as geneva said... my bet's on that side --- a case of beer!

As before, that's kinda what I think too, hell half the fun of airboats is tinkering around with stuff that ain't broke. 8)

"If it ain't broke, find out why."

 

[T-REX]

now thats funny..........."if it aint broke find out why" thats the funniest thing ive heard in months!!!!!
thanks for the smile.

 

[bondsman]

it is not so much finding out why it aint broke its just there are so many great ideas on this site that every time one pops up i think wow that is a great idea.and next thing you know $10 here $100 there.this forum is worse than a meth addiction.

 

[FP1201]

FWIW: The narrower 66x36 didn't make as much thrust as the wider 66x34, both turned the same RPM's (~2,500) The PE90 just won't spin any faster and at that speed it still sputters....gotta have that mag checked out.

 

[leo_081103]

as expected. there may be some descrepancies but it is general in nature.

flatter pitch props have better thrust. this on a basis of trading extra pitch for blade area. as the example the 66 x 38 ( or is that 36?) narrow prop has four more inch pitch than the 66 x 34 prop. so, in order to load the engine similarly as 66 x 38, the 66 x 34 must have a wider blade since it has a lower pitch.

wide props push more because they sweep a larger volume of air but at a lower slipstream speed thus you compromise top end. on the other hand, narrow pitchy props has better snap because their air volume effectivity is much dependent on rpm and they load the engine less at lower rpm thus it seems they pick-up rpm better. pitchy props will throw less air volume but at a higher slipstream speed. this of course considers that you dont have stalled blades.

by this, as well as an accepted fact that to get better thrust, a prop must throw a large volume of air at reasonable speed rather than move a small amount of air at very high speed. this reminds me the claims on the superwides paired with a 2.68 now, if only we could trade that tons of pitch for area :thumbleft:

well, we can only go so wide....... later

 

[goldhunter_2]

FP1201,
do you still have Gpu cylinders and pistons and single mag on there?

on my PE-90 I tried a 66x36 and was not enough prop so went to a 68x38 and as long as I was carefully I didn't spin it over 3000 I was going to try a 72" prop but then started the new boat......... I guess what I am tiring to say is I would have thought you would swing that 66x36 super easy at 3K

 

[hmgm123]

A 68x38 prop is a 200 lycoming prop that is a big prop for a pe90.

 

[FP1201]

FP1201,
do you still have Gpu cylinders and pistons and single mag on there?

on my PE-90 I tried a 66x36 and was not enough prop so went to a 68x38 and as long as I was carefully I didn't spin it over 3000 I was going to try a 72" prop but then started the new boat......... I guess what I am tiring to say is I would have thought you would swing that 66x36 super easy at 3K

Other than the addition of a 2V Holly carb, I'd say she was bone stock with a single (L) Slick impulse mag and one hole cylinders. See the 66x36 was a spair prop from my Uncles old boat and it had a 125hp Lycoming and his primary was a Sensenich 66x36 he had no trouble turning either one. The 66x34 was made by "Air-Props" and is noticably wider than the 66x38 ~2' wider.
The engine breaks up at WOT almost like it' running out of fuel or hitting a rev limiter.
Plugs: new and gapped @ .018
Wires: Belden with proper ends inside an AC dist. cap (which I haven't removed, yet)
Fuel pressure: ~5psi pretty constant, little higher above 1K. Fuel is a 4:1 mixture of 93 and 100LL, new fuel/water seperator, 3//8" fuel lines.
Carb: Clean as new, starts right up every time, no smoke at idle, some blackinging on the cage & prop, but nothing that concerns me, little puff of blue on the (R) bank at start up, leaks more oil than it burns.
Overall it seems to run strong and constant up to ~2,400 RPM, after that you instinctivly back off because it's just not running right.
Past history: This boat sat un-used in a storage barn for three or more years until I bought it and the day we drug it out to listen to the engine, the owner fiddled around trying to squeeze the primer bulb on the hose, but the are harder than radial tires when the temp is twenty degrees outside. :shock: That said, once the bowl was filled and a battery hooked up, about three or four turns and it was running. (and I know it wasn't run or tried before just becasue ou all the debris we had to clean out before turning it over).
If this were a tractor or maby any other old engine with points and condenser, they would be top on the list to replace, but I'm a bit shy about tearing into a Slick "Throw Away" mag, especially when I don't have a replacement or 2~3 hundred dollars to have it overhauled. On the downside is "Paddleing" sux.

 

[FP1201]

A 68x38 prop is a 200 lycoming prop that is a big prop for a pe90.

Seems my Dad had a 68x38 on his O-320 Lycoming, and it was a very strong engine.(he said it was 160hp, but ran the same as his friends O-360) he had to be carefull not to overspin the 66x36.

Horsepower rateings seem to be all over the place with PE90's: 110, 125, 150,... capable of 200 :shock: I would certainly like more power, but as long as it'll spin the prop on it now, it'll be alright....just cure the breaking up.

 

[hmgm123]

check your mags then your intake tube for leaks, then your fuel pump for fuel delivery.

 

[goldhunter_2]

A 68x38 prop is a 200 lycoming prop that is a big prop for a pe90.

It ain't all that big. I believe Sensenich rates there 68x38 prop at 180 to 200 hp


FP1201

Horsepower rateings seem to be all over the place with PE90's: 110, 125, 150,... capable of 200 Shocked I would certainly like more power

the PE-90s are easy to upgrade and depending on what you do is where all the different ratings come form . You can do lots of stuff one thing at a time for money reason , pistons, 470 or 520 jugs , 2nd mag

if you just the motor and it set that long probably would not be bad idea to pull in apart it pretty easy even I can do them :lol: those lifters are bad after sitting and could need cleaning also the oil leaks with those old paper gaskets if they have set an dried out they are going to leak buckets... I can testify to that fact personally :lol:

 

[FP1201]

check your mags then your intake tube for leaks, then your fuel pump for fuel delivery.

Feelers are being sent out right now to have the mag tested.
The clamps and rubber sections on the intake tubes seem to be tight and in good condition...somewhere I've got some silicone hose that would make and excellent replacement, and that'll happen as a matter of course.

I made an in-line fuel pressure tester that used a low pressure gauge from an actylene regulator. pressure is good, flow wasn't tested, but seems to be acceptable. It doesn't really act like it's running out of fuel...that's kind of like bogging down and jumping back up and should just about starve the engine out by running the bowl dry before enough can be pumped back in...hasn't sputtered until it died, also the sputtering while consistant, doesn't always do it all the time, once in a while it'll go like hell, then it's back. when that happens, it'll snap up ~2,800 but doesn't hold it....maby it's just tach flutter. :?

 

[FP1201]

A 68x38 prop is a 200 lycoming prop that is a big prop for a pe90.

It ain't all that big. I believe Sensenich rates there 68x38 prop at 180 to 200 hp


FP1201

Horsepower rateings seem to be all over the place with PE90's: 110, 125, 150,... capable of 200 Shocked I would certainly like more power

the PE-90s are easy to upgrade and depending on what you do is where all the different ratings come form . You can do lots of stuff one thing at a time for money reason , pistons, 470 or 520 jugs , 2nd mag

if you just the motor and it set that long probably would not be bad idea to pull in apart it pretty easy even I can do them :lol: those lifters are bad after sitting and could need cleaning also the oil leaks with those old paper gaskets if they have set an dried out they are going to leak buckets... I can testify to that fact personally :lol:

Are or do you know if the jugs from the PE150 (220hp) are the same?
With dual plug O-470 cylinders aren't the intake and exhaust on the bottom?
Dual mags would be nice and there IS a noticeable improvement in performance, but the jugs in this engine won't accept another plug hole (unless I completely missed something)
The oil leak(s) aren't too bad, after ah hour or so there are several drops, but not more than can be wiped up with a paper towel or two. (it's also got AeroShell W65/SAE-30 in it).

 

[goldhunter_2]

The Pe-150 (220) jugs are the same exact jugs as the Pe-90 so there is no benefit to changing that way. the 470 jugs yes are dual plugs and the intake is on the bottom witch you could run a aircraft carb then or I saw one the other day that had long intake pipes come form the bottom and curve around to the spider on top. the 470 jugs will bolt right on with out any machine work , that's what the Pe-150 are doing to get the 220 name . there was a thread on ere a few months ago where someone turned over the jugs so intake was on top but that is all I can tell you about that method . if you try 520 jugs you need to have the case bored witch you need to strip in down to the bare case for that also

is there a difference in performance?......... I personally say yes and think others would agree the dual plugs, dual mags and upgraded piston and jugs there is a difference. look at it this was your trying to turn a 66x34 and cant get it over 2500 rpm on my PE-90 with the upgrades I was spinning a 68x38 and wanting to move you to a 72 witch I believe it would swing so I would say there is a difference

 

[FP1201]

... there was a thread on ere a few months ago where someone turned over the jugs so intake was on top but that is all I can tell you about that method ...

Sounds like the one about the "Lyconentinal" where a set of GITSU jugs were hung on a Lycoming block (cam on top vs bottom)
The local FBO mechanic was working on a Continental and when I told him about it he gave me the biggest WTH look, then started thinking about it. :lol:
Thanks again for all your input!
P.S. Just to make sure, I'll run a compression test & leak-down test this afternoon, maby even use the cyl. inspection scope a late friend gave me. 8)

 

[Tony480]

If your RPMs are flucuating between 2500-2800 I would almost guarantee you have a burnt distributor block in your mag.Easy fix though.