Prop Data (new and old) Do I need to go lower?

Just put a new prop on that I picked up off ebay for about 50.00 bucks and took boat out this morning. With the old prop I thought the RPM's were too low. Looking for some input to see if I should go lower or leave it alone. Everyone on here said to either go with a 15 or 17 pitch prop. Found a good deal on the 17. Do I need to go down to the 15?


Boat
1996 Sunbird Spirit 170 17.5 ft
Dry weight
1900 lbs- per internet
Engine
1996 Evinrude 88 SPL

2 people in boat/10 gallons fuel/50 lbs stowed gear

Old prop
Material-SS
13x? - Had no markings on it at all
RPM's- 4100 WOT
Speed-32 MPH- Boat speedo
Got on plane ok

New Prop
Material- ALUM
13 1/4x17
RPM's-5000 WOT
Speed-35 MPH GPS
Jumps on plane quick

Re: Prop Data (new and old) Do I need to go lower?

Your right in the middle of the rpm rating your slip is about 13% a little high but acceptable.
Is the anti vent plate about even with the bottom of the boat?
If you don't have any venting issues you may be able to go higher.
Could add some rpm and speed.Have you played with the trim.
If its manual trim usually one notch isn't quite enough but one more notch is too much.
You can buy or make wedges to make it more or less 1/2 a notch.
Of course you can move around or remove weight.

Re: Prop Data (new and old) Do I need to go lower?

Yes the anti vent plate is even with the bottom. As far as I know this is the original package that came with the boat brand new. Nothing has been moved as far as I know. It also does have power trim. The numbers I listed were with it trimmed as best as I could, it was a little rough on the lake today. I am pretty happy with the performance of everything, my main concern is that i wanted to opereate the engine at the correct RPM. What do you suggest to go up too. I thought if I went higher I would loose RPM's. This prop stuff is like a science.

Re: Prop Data (new and old) Do I need to go lower?

JGra said:

I thought if I went higher I would loose RPM's. This prop stuff is like a science.

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I think those OMC engines were rated 4500 to 5500 with 5000 being where you could realize rated hp. Used to be that way anyway. When you add pitch you load the engine more. Loading drops rpms unless the increased pitch increases the boat speed which usually gets the boat higher on the water. With less water contact, there is less drag for the available hp to push against, more mph, allows the rpms to come on back up and if everything were perfect, you would hold your rpms and get more speed. But things are seldom perfect.

Mark

Re: Prop Data (new and old) Do I need to go lower?

Yes going to a higher pitch than your 17 would very likely lower your rpm as mark says could result in more speed though but then the mystery is at what rpm.I feel lower than present. You could try a 19.You just may end up with a brand new spare.
Again if your not having any venting issues you could try raising the motor a hole and see what you get.
You could go to the Turning Point site and select a Hustler prop they are said to give SS performance at AL prices.Get the newer style. As I understand it the old style is being discontinued.

Re: Prop Data (new and old) Do I need to go lower?

Thanks for all the info, I am pretty satisfied with the RPM and speed so I think I am just going to leave it where its at and have some fun with it.

Re: Prop Data (new and old) Do I need to go lower?

5000-5200 rpm is perfect for that motor. Leave things alone.

Re: Prop Data (new and old) Do I need to go lower?

JGra said:

Thanks for all the info, I am pretty satisfied with the RPM and speed so I think I am just going to leave it where its at and have some fun with it.

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Smart answer. You don't have to spend any $$$, don't have to fool with anything, and you know the outcome and are satisfied with it.

Happy camper.

Mark