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Help in Re-Propping Boat?

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Old 04-19-2011, 06:46 PM
  #1
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Default Help in Re-Propping Boat?

I want to thank everyone for helping me so far on getting my (new to me) boat up and going this season. I have taken it out 4 times now and it has been an absolute blast.

I want to make sure the boat performs the best it can. I want to go fast without sinking in too much money.

The boat is a 1995 22' Scarab with a Merc 260 and a Alpha Drive (1.55). I currently have a 22 pitch 4 blade prop on the boat.

I am going to always have the boat loaded with people. It seems to be setup for about 400-500 lbs in the boat. I have double that when I am running the boat.

The engine is rated to run 4600-4800 RPM. I am currently running a maximum of 4500RPM at about 50MPH. If I run the boat by myself, I can get it to 4800RPM right at 58-60MPH.

I have looked at several threads, trying to figure out what to do. In my mind I have two options:

Option #1 - More Power: I have read that I can buy 1996 or newer Vortec heads and intake and do a simple bolt on switch and get 300HP out of the motor for under $1000. IF this is true, this would be ideal, since I would be able to use my current prop and increase the power 40HP and get the RPMS up to 4800, and get the speed up to 60+MPH. Can anyone confirm this or give any advice??

Option #2 - Smaller Prop; I have also read that it is important to have the boat right at that "sweet spot" in the RPM range and that number is 4800RPM. If I go down to a 19 pitch prop, I should be able to get to that RPM number and since I am spinning a smaller prop faster, I might be able to maintain my current speed and maybe increase it a bit.

If Option #2 is the option to chose, what prop should I go too? My marine mechanic is recommending a "19 pitch High Five Prop". I even found a good used Stainless High Five for $250 here in Phoenix.

OR... should I go with a 19pitch 4 blade or even a 19 pitch 3blade??

I can sure use the advice!! Thanks again everyone!!
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Old 04-19-2011, 07:18 PM
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Cheap and fast don't really go together.

A big block drop in would be great if you can make it happen. Either way, good luck
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Old 04-19-2011, 08:40 PM
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Sounds like you are propped pretty good right now. 4800 rpm's by yourself is what your red line is according to your post. If you are loaded down with people might try a little more trim. If you go to a 19 P think you will have to many rpm's
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Old 04-19-2011, 10:01 PM
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Quote:
Originally Posted by firehawkcat View Post
Sounds like you are propped pretty good right now. 4800 rpm's by yourself is what your red line is according to your post. If you are loaded down with people might try a little more trim. If you go to a 19 P think you will have to many rpm's
X2.. Maximum RPM and speed is calculated with the Boat basically empty (1 person, 3 eyedroppers full of fuel, anchors left on the dock, etc). Don't try and replicate it with a full Boat, It's not going to happen.

If you want to go faster, more HP
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Old 04-19-2011, 11:44 PM
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Quote:
Originally Posted by firehawkcat View Post
Sounds like you are propped pretty good right now. 4800 rpm's by yourself is what your red line is according to your post. If you are loaded down with people might try a little more trim. If you go to a 19 P think you will have to many rpm's


X3. I'd leave it as is........ and spend the money on fuel. You'll be happier at the end of the summer.


Darrell.
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Old 04-20-2011, 12:09 AM
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I had the same hull I believe but a '97 with a 300hp 7.4liter, turned a 25 mirage plus @ 4600 rpm at 62mph 2 people 30 gallons fuel for a comparison. My scarab 22 liked the mirage plus best because it would lift the bow. I tried other props but it was always the mirage plus that would get the best performance. You might gain 2 mph with the 40 extra hp, and that would need to be a true 40 hp gain (torque) to turn a higher pitch prop. Best thing I ever did was not touch the motor in my scarab 22! Enjoy and then move up later to another boat.
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Old 04-20-2011, 11:36 AM
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I appreciate all of the posts.

The boat does move pretty good. I pass most of the boats on the lake with no problem.

90% of the time, I will be running the boat loaded and if changing to a 19P prop wont make a lot of difference, I will stay where I am at.

I was told that if I am running under the 4600-4800RPM range, that I need to get a lower pitched prop to compensate and bump it up a bit. The mechanic also said that it would give me a better "hole shot" as well.

I know it is good to have a spare prop (just in case), so I might just buy a 19P and switch it on and off and see how it does. If it makes it better, keep it on. If it make it worse, just use it as a back up prop. (Does that sound like a good idea?)

Thank you everyone!!
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Old 04-20-2011, 11:40 AM
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Quote:
Originally Posted by pitts1313 View Post
I had the same hull I believe but a '97 with a 300hp 7.4liter, turned a 25 mirage plus @ 4600 rpm at 62mph 2 people 30 gallons fuel for a comparison. My scarab 22 liked the mirage plus best because it would lift the bow. I tried other props but it was always the mirage plus that would get the best performance. You might gain 2 mph with the 40 extra hp, and that would need to be a true 40 hp gain (torque) to turn a higher pitch prop. Best thing I ever did was not touch the motor in my scarab 22! Enjoy and then move up later to another boat.
Appreciate the advice!! I believe you are right. I need to leave the motor alone and just pickup a 19P spare prop (I need a spare anyway). I will spend the money on a better stereo and more beer (for the passengers, of course!) :-)
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Old 04-20-2011, 01:05 PM
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Quote:
Originally Posted by chris50smith View Post
Appreciate the advice!! I believe you are right. I need to leave the motor alone and just pickup a 19P spare prop (I need a spare anyway). I will spend the money on a better stereo and more beer (for the passengers, of course!) :-)
A good all around prop would be a turbo 2+2th,,its a great all around prop..i reccomend a 20 pitch

http://www.turbo-props.com/products/...th-series_th22
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