13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

[MickLovin]

HI guys, I have a Chrysler 100HP 1979 model on a 17ft Carribean Half Cabin 1980 model. My question is, before this s/s prop the old Chrysler had a 23" pitch and I was getting around 45MPH, I changed to my 21" prop which came off my 75hp Chrysler. To be honest I haven't done a complete water test with the 21" prop, what could I expect to find with the s/s prop. the 23" was an aluminium original and the s/s 21" prop is a volvo penta prop #511-21 and the number for my 23" was 528-23.
Also I do a lot of fishing either outside or in the river, are these the best props for my set-up or am I better obtaining a 17" or 19" s/s prop? I found in my manual that the 100 HP should have a 19" so why would it come standard with a 23"?

 

[steelespike]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

Unfortunately we need more information.If you read the stickys at the top of the prop forum and get his as much info as possible
we can help you.
It does seem to me that a 23" pitch is a lot of prop for a 1/2 cabin.
Very likely some one was fiddling with props and not understanding prop theory.
Any motor needs to be propped to produce the rated rpm at wot.
Your manual should list this and also we need the gear ratio.Higher pitch numbers are harder for the motor to turn lower pitch numbers are easier to turn.
We need your wot rpm and gps speed with your 21" prop because it is closest to the manual suggestions.
The 19" suggestion may not work if you run with a heavy load or perhaps ski with a load of people.
As your motor ages you may have to lower the pitch.

 

[MickLovin]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

Ok I was getting 4500 rpm at 45 mph with the s/s prop 21", but I do run a heavy load, it has a 80 litre fuel tank, 2 x batteries and a bag of heavy tools in case .
My manual has spec'd a 19" aluminium, so at 19" I might get the 5500 rpm specd? I doubt it would make 1000 rpm difference. My motor has 150+ compression and it is running fine.

 

[jestor68]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

I assume your manual says that it develops it's rated hp at 5000 rpm, with a range from 4500 to 5500 rpm.

The industry standard expectation is 150-200 rpm change per inch of pitch change.

It probably didn't come with a 23" prop; more than likely someone put it on there thinking more pitch means more speed; which is true to a point.

 

[krakatoa]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

I believe that 21 pitch it too much for a 100hp, just test last Sat a Stiletto 13x21 in my OB 115HP and I found that this pitch is too heavy to perform, it allow to run the OB in very low RPM, that may cause to overheat the engine, for me the best option is 13x17 or 13x19....

 

[Frank Acampora]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin



You know, Mick: I have been staying out of this thread for a while. I really don't think that your numbers are accurate OR, your engine is not a 100HP.

In my experience with Chryslers, 21 pitch on all but the smallest boat is too much prop for a 100 HP engine. The photos above show a 15 foot light (700 pounds bare) Glastron deep vee with a 105 and 19 pitch prop. She just about touches 45 at (if I remember correctly) at about 5000RPM with me alone in the boat. Second photo is a 14 foot flat bottom with a 90HP Force. SHE uses a 21 pitch prop and turns 55 at 5500 RPM. A 125 turned the prop at 5900 and gave 60 MPH.

HOWEVER Prop design is important. I have used a Ballistic prop and it dropped the RPM down to 4500 but speed remained the same. Also, speed was measured with a GPS on a river and not both ways averaged so subtract a couple of MPH for current.

 

[MickLovin]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

My tacho could be wrong, it is a new digital which you have to set it's parameters by putting in the number of poles and rpm which is numbered to scale the tacho. It may have been 40 mph but I was sure I saw 45. I think it would be wise to buy a 19" anyway or even a 17" .
Actually I am buying a 85hp Chrysler Charger for $200 next week, hopefully it will have a 17 or 19 on it.

 

[MickLovin]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

ok just thought I would post a pick of the old and the new props

old prop

The new prop is a 13 1/4 x 17"
The old one 13 1/4 x 21"

 

[jestor68]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

Now I know where all the nice Chrysler motors have gone.

A 19 should get you around 5000 rpm, while the 17 should get you closer to 5500 rpm.

 

[Frank Acampora]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin



Don't mean to make it a pissin contest but I have one too! Only, mine is better 'cause I have two: One with the flare washer (stock) and one without (Ballistic)! Nya-Nya!

I see that the new prop is fully cupped. I think that makes it a bow lifting prop.

 

[krakatoa]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

View attachment 228229View attachment 228230

Don't mean to make it a pissin contest but I have one too! Only, mine is better 'cause I have two: One with the flare washer (stock) and one without (Ballistic)! Nya-Nya!

I see that the new prop is fully cupped. I think that makes it a bow lifting prop.

I cant wait to test one of those ballistics props...

 

[MickLovin]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

View attachment 228229View attachment 228230

Don't mean to make it a pissin contest but I have one too! Only, mine is better 'cause I have two: One with the flare washer (stock) and one without (Ballistic)! Nya-Nya!

I see that the new prop is fully cupped. I think that makes it a bow lifting prop.

Just because it has a RED nose cone doesn't mean it will go faster , so nya, and I have the flare washer (stock) and another nose cone which is white so nya. Mine is a Michigan dunno what that means , but I love the way the nose cone pops it's head out.

 

[Frank Acampora]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

Yeah! The red one pops out kinda like a dog around a ***** in heat. LOL edit---OOOOH! It won't let me use the proper term for female dog! Come on iboats. A male is a dog and a female is a witch with a "B". That's life and American language, and the family and kids should know the proper terms AND their proper use.

 

[Texasmark]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

View attachment 228229View attachment 228230
I see that the new prop is fully cupped. I think that makes it a bow lifting prop.

Rake makes for bow lifting with Rake defined as the slope of the blade (fore to aft) after it leaves the root. The attached thubmnail is my 24P Ballistic which I ported. Note how the trailing edge of the blade is far behind the start of the root. With no rake, the blade would be positioned directly out from the root like a fan in your house.
Cup helps helps to prevent ventilation at high mounting/trim angles and in tight turns where there is turbulence from the hull. Thin blades cut the water easier and thus run higher rpms for a given prop.

The 21 SS may run better than your 23 assuming both are not too much prop for your engine due to thinner blades, blade geometry including rake which will reduce the wetted area of the boat and thus reduce drag resulting in more rpms and speed. The cup of the 21 will probably put it's thrust at or near that of the 23 if everything else were identical.

My 2c and learned via experience.

Mark

 

[MickLovin]

Re: 13 1/4" x 21" pitch stainless prop on Chrysler 100HP 17ft Half Cabin

Thanks Mark for your comments, just waiting to try the 17" now, let you know how it goes.