Will this prop work?

[glastronomic]

Propellor Question;
Have a 21ft boat, 165HP mercruiser, that runs great on it's original prop; 17 Pitch 16 diameter. (48 66450 AS4 17P) but getting worn out a bit.

Have also a still new 13 3/4 diameter 21 pitch propellor. (48 79576 A4 21P)

Would it run similar with the 13 3/4 21P as with the original 16" 17 pitch or better to get another 16x17P?
Thank You all in advance for your wisdom.

 

[achris]

Re: Will this prop work?

Putting a 21" prop in place of a 17" will drop your max revs by around 800rpm, and cause your engine to be SERIOUSLY overloaded... If you are getting close to 4300rpm with the 17" then get another one of those. If your only at about 3900-4000, then drop down to a 15"....

Love the Savage Bluefin.
Is that the Hillarys marina?

Chris.......

 

[ziggy]

Re: Will this prop work?

generally speaking.
an inch of prop pitch is worth aprox. 200 rpm. like achris is describing.

i had a 21p on my 165hp when i got it. a 19' boat. my wot was 3900. the low end of the spec. i went to a 19p and gained 400 rpm. now my wot is 4300. right at the top of the spec. 3900-4300. generally speaking. you want your wot rpm right at the top of the spec.

your boat is 2' longer than mine and probably heavier. i'd think stick with the 17p too. it just depends on what your wot rpm is. speaking of which, what is your wot rpm? that will give folks something to chew on so they can offer their ideas..

Love the Savage Bluefin.

ya, ditto on that. very nice boat..

 

[steelespike]

Re: Will this prop work?

You guys are missing he says the 17" pitch is a 16" diameter 2 1/4" inches bigger.I think he needs to measure the 17
to confirm the diameter. I'd have to wonder if the 16 barrel is bigger than the 13 3/4?If you measure from center to the tip of a blade and double it will give the diameter.A 16 X 17 would surely turn slower than a 13 X 17 A 21 isn't going to work and the 16 diameter would normally be found on a heavy application perhaps like the boat in question.

 

[glastronomic]

Re: Will this prop work?

Measured the prop and it is a 16" one on the boat.
the spare one is 13 3/4".
Does the smaller diameter compensate for the steeper pitch?


To Achris; Picture taken @ Ocean Reef Marina, 6km's further North.
Best boat i have ever owned.
Lived, with previous owner, for a great many years @ Hillaries Yacht Club!
Yersterday morning, 1-1-2012 first session of the year! out of O/R

 

[steelespike]

Re: Will this prop work?

Wouldn't hurt to give us the details of your present performance.
It will give us an idea of how well your setup is working.
Diameter will make up for some but
I don't think the it can make up for a 4" pitch change Won't hurt to try it
And it will give you some different numbers to work with. I believe the 165 is rated at 4600.
That a lot of boat for a 165.

 

[glastronomic]

Re: Will this prop work?

engine runs WOT @4200 rpm and 30 knots.
accelerates seriously fast
Boat could be 2 ton all up with 200ltr fuel and 50ltr of water.
I realy never run WOT almost all times between 2500 @ 3000rpm doing 17-20miles/h which the boat clearly like to cruise on.
I guess the best way is to bolt the prop on and go for a testride.
If I get another new 16"/17P prop then it will be a Stailess Steel number as these pollised up are also acting like a teaser while trolling I think.
But, they are pricey here in Australia.
Boat's max HP rating is 200HP from factory back in 1978 I believe

 

[achris]

Re: Will this prop work?

You might find it hard to get a new 16"x17" prop nowadays. They were originally designed for large boats with high torque engines, like the 454s. The change in diameter won't cause much difference if the pitch is the same. I would go for a 17" SS prop, either a Vengance or a Laser II with the vent plugs in. If the boat benefits from the larger diameter (which gives bow lift) then a 15" Mirage MIGHT work quite well. A Merc dealer should be able to give you a loaner and you just keep changing them until you find a prop you like, then buy that one. What I did when I changed my engine was to find a good 2nd hand one on eBay and go from there. If you don't like it, resell it....

I forgot to ask... It this '165' a six inline or a 4 inline?

Chris......
I'm usually out from Cockburn to the back of 5 fathom bank or south of Rottnest. Sometimes I trail mine up to Port Gregory and head over to the Abrolhos for a couple of days.... Some FANTASTIC diving and fishing out there!!! And I'm currently in Norway freezing my bits off. Today we will be signing onto a boat heading out to do some deepwater trials (4,000metres) between Scotland and Iceland... How much fun will THAT be????

 

[achris]

Re: Will this prop work?

You guys are missing he says the 17" pitch is a 16" diameter 2 1/4" inches bigger.I think he needs to measure the 17 to confirm the diameter. ....

We didn't miss it, it just not that relevant... And yes, they did make them that big, they were referred to as 'elephant ears'....

 

[achris]

Re: Will this prop work?

Wouldn't hurt to give us the details of your present performance.
It will give us an idea of how well your setup is working.
Diameter will make up for some but
I don't think the it can make up for a 4" pitch change Won't hurt to try it
And it will give you some different numbers to work with. I believe the 165 is rated at 4600.
That a lot of boat for a 165.

165 was recommended max rev 3900-4300rpm. I had a 165 in my boat for the first 8 years of owning it, and got 4250rpm at 30knots with a 15" prop. His boat and my boat are very similar in hull shape and mass. And I have seem 165s put in a lot bigger boats than ours.

 

[glastronomic]

Re: Will this prop work?

I can get a 16"- 16 Pitch no problem Michegan Match 031051 in ali.
So it is 16" and not 17P.
This why I posted the question as no perfectly matching prop is around it seems.

 

[achris]

Re: Will this prop work?

17P means 17" pitch... Most of the large diameter props were even pitch, I've never seen one with an odd pitch....

 

[glastronomic]

Re: Will this prop work?

You might find it hard to get a new 16"x17" prop nowadays. They were originally designed for large boats with high torque engines, like the 454s. The change in diameter won't cause much difference if the pitch is the same. I would go for a 17" SS prop, either a Vengance or a Laser II with the vent plugs in. If the boat benefits from the larger diameter (which gives bow lift) then a 15" Mirage MIGHT work quite well. A Merc dealer should be able to give you a loaner and you just keep changing them until you find a prop you like, then buy that one. What I did when I changed my engine was to find a good 2nd hand one on eBay and go from there. If you don't like it, resell it....

I forgot to ask... It this '165' a six inline or a 4 inline?

Chris......
I'm usually out from Cockburn to the back of 5 fathom bank or south of Rottnest. Sometimes I trail mine up to Port Gregory and head over to the Abrolhos for a couple of days.... Some FANTASTIC diving and fishing out there!!! And I'm currently in Norway freezing my bits off. Today we will be signing onto a boat heading out to do some deepwater trials (4,000metres) between Scotland and Iceland... How much fun will THAT be????

Mine is a 6 cilinder 165HP engine.
In Oil & Gas for a job?
So am I; instro/elect tech.

 

[steelespike]

Re: Will this prop work?

engine runs WOT @4200 rpm and 30 knots.
accelerates seriously fast
Boat could be 2 ton all up with 200ltr fuel and 50ltr of water.
I realy never run WOT almost all times between 2500 @ 3000rpm doing 17-20miles/h which the boat clearly like to cruise on.
I guess the best way is to bolt the prop on and go for a testride.
If I get another new 16"/17P prop then it will be a Stailess Steel number as these pollised up are also acting like a teaser while trolling I think.
But, they are pricey here in Australia.
Boat's max HP rating is 200HP from factory back in 1978 I believe

Assuming a 1.7 gear ratio 4200 @ 34.6 mph is about 13% slip respectable for a heavy boat.
A boat with quick hole shot that stays on plane at @ 2500/17 mph with wot right on 4200 and apparently trolls well seems like it would be hard to improve on that.Maybe I'm too easy to please.

 

[achris]

Re: Will this prop work?

...In Oil & Gas for a job?
So am I; instro/elect tech.

Yep, ROV supervisor/pilot....
Heading out to the North Atlantic (in mid-winter!!!) with a couple of brand new Schilling HDs on board....
(goggle 'AMC Connector')

 

[glastronomic]

Re: Will this prop work?

Assuming a 1.7 gear ratio 4200 @ 34.6 mph is about 13% slip respectable for a heavy boat.
A boat with quick hole shot that stays on plane at @ 2500/17 mph with wot right on 4200 and apparently trolls well seems like it would be hard to improve on that.Maybe I'm too easy to please.

http://youtu.be/ba_kvI88OHw short video of it cruising

Gear ratio : 1. 65:1.
Yes It feels good and like to keep it the same, Do not want to "Improve" just a new prop as this one seems from 1978 and has seen better days.
I am going to go to a Mercury dealer here and have a chat to see what is available, as close as this, to replace.

 

[steelespike]

Re: Will this prop work?

I guessed 1985. Under certain conditions an al prop can actually become undersized from wear especially in silty conditions.
I guess in over 30 years a prop could be over due for replacement and maybe even an improvement in technology.

 

[rolmops]

Re: Will this prop work?

48-66450-as4 (48-66440) is the Mercury equivalent of Michigan031051 and 992003,993043,993023 and 993203 with this info go to the Michigan website below and look at pages 20/21 and 31/32.
http://www.propline.com/Propeller-General-Information/Michigan_Wheel.pdf

 

[glastronomic]

Re: Will this prop work?

Now the next question;
How do you pull the propellor, after having undone the nut and washer, of the driveshaft when it has been there for a great many years, without damage to the shaft and 90degree drivecog & bearing?
It refuses to leave it's place and it being aloy plus the shaft being SS , there might be a wee bit corrosion.
Heat prop up? or is there another method like a kind of bearing puller/prop puller?
Rolmopsie, my favourite fishy snack bye the way, I have the Michigan Wheel 2010 catalogue , Thank you for your effort never the less

 

[achris]

Re: Will this prop work?

If it hasn't been off for a good few years you may need to convince it with an CIG tools kit (hot spanner).... That will likely destroy the hub, but it may be the only way to get it off. A puller in conjunction with the hot gun will be the way to go...

I make my own rollmops .....