PROP’s Wow can this get confusing!! HELP

OK, So I have been on a crash course with props over the last few days. Perhaps I am overthinking this but I just do not know. here is what I do know:
I currently have a 2000 Johnson 130 on an 18′ H56 Xpress boat with a manual jack plate. The current prop is a Raker 14-1/2 x 20pitch The RPM’s run at the 5800-6000 right now which engages the rev limiter, in essence it causes a cylinder to drop cutting the motor power so you do not over rev the motor. I also have a porpising issue at the top end.
Trying to resolve both issues, dropping the RPM’s by 200-400 the power band is supposed to be at 5500rpm, and to help the porpising has brought me to:
Needing to increase the pitch to a 21 and possibly a 22 with a 3 blade prop. A 4 blade prop I would also be looking at a similar 21-22 pitch (from what I am told)I have been told that every pitch jump should reduce the RPM’s by about 200. Now do I need to stay with the 14-1/2 diameter, I am told this is not necessary but depends on the type of prop.
OK so I am looking for recommendation of type of prop etc. Money is a bit of an issue so I am not looking to spend huge $$. So can anyone help? The more I learn the more confused I get!
Thanks
Jeff

Well the first thing I would do is lower your jack plate and see what that does for you. It should reduce some rpm’s so you arent hitting the rev limiter. The other problem is when running a jack plate if the motor is set high the prop should be double cupped to hold the water better. Cupping usually cost $60-80. Cupping will also decrease rpms’s depending on how much and given boat.

You could try a bigger pitch like mentioned but I would stick with the same prop you got now just bigger pitch. Cause even if you have 2 different props that are 20p they wont pull the same rpms. By switch to a different brand in a 21p could change your rpms ????.

Thats where I would start hope it helps.

Perhaps this post should be in the Outdoor Gear forum? Can someone help me move it?
Thanks

Well you might not get alot of replies as not many guys change anything from the what the dealer set up. If I wasnt of any help I would call a prop/performance shop and see what they say.

Thanks Skeeter,
YOur reply was helpful. I have spoken to BBlades in Prinston WI. Really nice guys there, but again the more I know the more confused I get!!

I would not bother going to the 21P I don’t think it will drop your RPM’s enough – I’d try the 22P – That may get you within the RPM range you want to be in. Droping the motor down may be the best option

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Thanks Skeeter,
YOur reply was helpful. I have spoken to BBlades in Prinston WI. Really nice guys there, but again the more I know the more confused I get!!

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The whole understanding props beyond just pitch takes awhile and it can make the head hurt . There are alot of good sites on the web that go in depth about props. Google search “prop pitch” along with prop pitch on most sites they talk about cup, diameter, rake, # blades….etc Another key thing to any prop and boat setup is the prop slip. There are calculators on web just search it. You wanna be between 10-15% slip 10 being better.

It sounds to me as though you have pretty close to the right prop but you just need to lower your jack plate. The porpoising at top end is caused by the prop not be able to hold enough water.

I would try lowering your jack plate by a quarter inch, and if that helps but isnt quite there gone down another 1/4″. That should help the porpoising issue and also cut a few hundred rpms off.

If none of that works than i would start playing with props.

Gotta agree 100% with Eric.

-J.

Thanks, I will give it a try.

i agree with eric also; i’ve only put in a couple of jack plates, but their height was very sensitive. I think you can get all the RPM reduction you are looking for with no more than 1/2″ max lowering…

Eric is right on with lowering the jack plate at 1/4″ increments. You will definitely know when your set down too far as the steering will begin to dramatically pull.

If you use your boat a lot throughout the year, you may want to consult with a true prop expert. I have all my props engineered and re-cupped with john at DHA Pro-pellers in Rochchester, WI. Its a little pricey up front to have done, but you will have a prop that is set up 100% spoecific to your rig and your expectations. An added bonus to an engineered prop that is done right is the significant improvement to your fuel economy. Most guys don’t consider that, but if your doing 6% to 8% better, that’s about $10 to $15 per tank.
These are the only guys that will ever touch one of my props!

Before calling, there is some info you will need to know
1. Weight of engine
2. weight of boat
3. Gallons of fuel you usually have on board
4 . capacity in gallons of live wells
5. Approx weight of gear
6. close estimate of average weight of passengers including yourself.
7. What are your expectations – Top end speed? Hole shot? best fuel economy?….

John was part of the Mercury racing team for many years and then was designing their props. He then moved on to his own company and is a super guy to work with.

D.A.H.® Custom Pro-pellers
34111 Washington Ave.
Burlington, Wisconsin 53105

John or Jeff Janaky
phone (262) 534-4440

Thanks for the help guys.
I just “stumbled” across this and it seemed pretty informative:
http://www.veradoclub.com/smf/index.php?topic=137.0
Transom height, and prop settings