Prop questions for a 2157 Carver Montego

[Tagerman]

Okay so I just bought a 2157 Carver Montego and I LOVE IT. I paid $4500 for it which considering the condition of the boat motor and interior I feel like I stole it. Now here is my question! The boat has a 5.7l Mercruiser with thunderbolt ignition and power steering. The boat is a 1990 and the outdrive is an alpha one. My prop is in awful shape just from being used it is the original prop I know since I bought the boat from the original owner. I can still get on plane pretty quick with the trim tabs but it could be better. How do i figure out my gearing and what size prop this should be I can't read the labeling on it anymore. Also would a 4 blade prop help me with the hole shot over the 3 blade. I'm not worried about top speed I'm coming from a 17ft boat that did roughly 20mph so this boat screams as far as I'm concerned once planed I barely run it over half throttle. Any help would be appreciated. I'm going out tomorrow and I'll grab the manuals off the boat (they basically have nothing useful in them) so if you need any other info tell me and I'll try to find it. The hull ID number is CDRB5096C090. I am a mechanic so I'm determined I will put this prop on myself and the marina mechanic wants to charge me to look at it.
Thanks!
Trent

 

[Bondo]

Re: Prop questions for a 2157 Carver Montego

Okay so I just bought a 2157 Carver Montego and I LOVE IT. I paid $4500 for it which considering the condition of the boat motor and interior I feel like I stole it. Now here is my question! The boat has a 5.7l Mercruiser with thunderbolt ignition and power steering. The boat is a 1990 and the outdrive is an alpha one. My prop is in awful shape just from being used it is the original prop I know since I bought the boat from the original owner. I can still get on plane pretty quick with the trim tabs but it could be better. How do i figure out my gearing and what size prop this should be I can't read the labeling on it anymore. Also would a 4 blade prop help me with the hole shot over the 3 blade. I'm not worried about top speed I'm coming from a 17ft boat that did roughly 20mph so this boat screams as far as I'm concerned once planed I barely run it over half throttle. Any help would be appreciated. I'm going out tomorrow and I'll grab the manuals off the boat (they basically have nothing useful in them) so if you need any other info tell me and I'll try to find it. The hull ID number is CDRB5096C090. I am a mechanic so I'm determined I will put this prop on myself and the marina mechanic wants to charge me to look at it.
Thanks!
Trent

Ayuh,... Take the prop off, 'n bring it to a Prop Shop to match it up with a new 1....
While you've got it off, ya might be able to read the part numbers, under the nut...

Ya should have a 1.50:1 gear ratio...

 

[Tagerman]

Re: Prop questions for a 2157 Carver Montego

Thanks!

 

[Tagerman]

Re: Prop questions for a 2157 Carver Montego

Okay new question on this topic that maybe someone can help me with. The prop is a 15" x 17 pitch. I have never owned a boat with a pitch that low but the motor wide open never revs above 4000 assuming my tach is correct. I'm looking to replace it with possible a 4 blade prop which I've heard good things about but I'm still a little iffy about changing prop styles. Would I notice a huge difference going from a 15" 17p 2 blade to a 14.5 17p 4 blade? Will this help my boat plane faster? and is stepping down a half inch in diameter okay? or should I go back with a 15" 17p identical to what is on the boat. She's never been in a hurry to plane but this current prop is ROUGH. Any help or suggestions welcome!
"

 

[Maclin]

Re: Prop questions for a 2157 Carver Montego

If you get a lot of slip taking off then a 4 blade will help, but I expect the RPM's would go down at the top end, unless the slip is bad there too.

To do proper calcs the formula needs accurate WOT RPM and MPH along with the prop pitch and drive ratio.

 

[Tagerman]

Re: Prop questions for a 2157 Carver Montego

Ok thanks, I'm hitting the water this weekend and I am a mechanic I'll take my tach from the show along with my gps and get some accurate readings! This thing needs a new prop bad I just want to get the right one especially since once you hit the water with them nobody will take the damn things back.