hwsiii---Need proping advice

[Proselect]

Re: Need proping advice

Re: Need proping advice

Ok Hwsiii, I finaly got out in the boat after turkey hunting last week and dealing with cool temps and terrible winds the last couple weeks. Tonight the water was like glass. I was really looking forward to letting it rip in the boat tonight. All I got was some disapointment.
First off I did a couple runs across the lake and consistantly ran the same numbers. Tonight I ran with what I consider my normal load. I had one bigger guy with me and my son and a bunch of fishing gear. We had over half a tank of gas.
I consistantly ran wide open trimmed up at 41.8 mph gps at 5250 rpm. I had my buddy try to take a few pics of the motor running in the water at WOT but he only got one. Of coarse my camera batteries died so he had to take the pics with his camera. He is going to email me the pic hopefully tomorrow. From what I could tell looking at the pic on the little camera screen the motor is pretty far down. It doesn't look like you can see the cav plate at all.
Now for the disapointment. The boat porpoised terribly. When my buddy was trying to take the pics it was really bad. When he moved up to the back seat it was pretty bad. If he moved up to the seat next to me( in the middle of the boat) it still porpoised. My son was always sitting on the step up to the front deck. I assume that is the reason the previous owner put the hydro foil on this thing. Now with it off with full load on very calm water, it bounces up and down the whole time regardless of speed and trimming one way or the other has little effect. Now I really want this thing fixed.

 

[Proselect]

Re: Need proping advice

Re: Need proping advice

H,
You must be pretty busy, you havn't been around as much on here. I am looking forward to seeing what you think about this situation.

For now I put the foil back on to stop the porpoising. I took it out again last night, same lake, same conditions. The foil killed my speed and rpm even more, but up on plane and nice and straight the whole time, no bouncing.

 

[Proselect]

Re: hwsiii---Need proping advice

TTT

I think hwsiii forgot about me.

 

[hwsiii]

Re: hwsiii---Need proping advice

Pro, I am sorry I have been busy. You need to move the motor up two notches on the transom and let see what we get speed wise and RPM. We need to get those RPM as high as we can, and the speed will follow, we also need to see how the porpoising is at that height and what blade geometry we need.



H

 

[Proselect]

Re: hwsiii---Need proping advice

Sounds good H, I will do that. I assume take the foil back off too once I move the motor up. I put it on for the time being to tame the beast. There goes my beautiful paint job Oh well, its only paint, once its figured out I guess it goes back in the shop for a respray of the rear end.

H,
What do you feel is a good speed for this boat/motor combo, not really looking for more speed as I am the rpm to be where it needs to be.
Also, is it likely I am going to have to change props at all? If possible i would like to save up for a SS prop in the future rather than buy a new aluminum. I have a week long anual fishing trip in a couple weeks and I am stashing money away for that.

 

[Proselect]

Re: hwsiii---Need proping advice

Here is a pic of the motor at WOT on calm water trimmed up. This is the original motor position. I will try to get a pic after I move the motor as well.

 

[hwsiii]

Re: hwsiii---Need proping advice

Pro, we don't need to do anything with the prop until we get the motor height right, so there is no rush on that.



H

 

[Proselect]

Re: hwsiii---Need proping advice

Well I moved the motor two holes up last night and tonight I took it out with the normal load again. I had little to no change in speed and rpm. I may have gained 50 rpm on one run but that was it. It still runs WOT at 5250 and gps speed of 41.8. I ran it without the whale tale on it and the porpoising was much better than it was before without it on. It does, however, still porpoise most of the time, but not nearly as bad. When we came across the lake right at dusk tonight the water was very calm. It planed off nice and we flew right across and then it started to porpoise a little. I trimmed all the way down and it still did it. When I backed off nearing the no wake zone it started to porpoise really bad at about half throttle. I am glad I know the results, but I was hoping it was going to be a lot better.

 

[hwsiii]

Re: hwsiii---Need proping advice

Pro, theoretically speaking, you have moved the motor up enough to put the whale tail back on the boat for your fishing trip, so it will stop your porpoising for right now.

Also, is it likely I am going to have to change props at all? If possible i would like to save up for a SS prop in the future rather than buy a new aluminum. I have a week long anual fishing trip in a couple weeks and I am stashing money away for that.

Right now your prop slip is at 1% and that tells me that you have more blade surface area than you need, because it is an aluminum prop with no real heavy duty blade geometry, unless it is a Turning Point Prop. Exactly what manufacturer and model is your prop?




H

 

[Proselect]

Re: hwsiii---Need proping advice

I believe the prop is an OE prop. It was put on (from what I was told) last year or late the year before. It is aluminum, painted black and has a part # 763463 on it. It also has the size- 13.25x17.

 

[hwsiii]

Re: hwsiii---Need proping advice

Pro, that is a BRP prop and they are very good, but if your numbers are right and I ams sure they are, then a SS semi cleaver will be perfect for your boat. When you get ready to order it just let me know.



H

 

[Proselect]

Re: hwsiii---Need proping advice

This prop would bring my rpm up where it is suppose to be? I assume if my rpms go up, my slip would go up, and my speed would go down a little?
Lastly, what is a SS semi cleaver? Is this something that is bought this way or something that has to be done to it? What size is it? I assume SS is stainless? Are there any aluminum options? I just want to price things out.
Thanks for your help.

 

[hwsiii]

Re: hwsiii---Need proping advice

Pro,

Also, is it likely I am going to have to change props at all? If possible i would like to save up for a SS prop in the future rather than buy a new aluminum. I have a week long anual fishing trip in a couple weeks and I am stashing money away for that.

I got lost, you said you wanted to purchase a SS prop, but now I don't know. An aluminum prop will run about $ 100 to $ 150 dollars and the staoinless prop that I will recommend will probably cost double that.

This prop would bring my rpm up where it is suppose to be? I assume if my rpms go up, my slip would go up, and my speed would go down a little?
Lastly, what is a SS semi cleaver? Is this something that is bought this way or something that has to be done to it? What size is it? I assume SS is stainless? Are there any aluminum options? I just want to price things out.
Thanks for your help.

Yes, your RPM will be much closer to where they should be. No, just because your RPM go up doesn't mean your prop slip will go up. And your speed shouldn't go down.

A semi cleaver is a type of prop, and you buy it like that. And it depends upon which one you get what pitch it is.



H

 

[Proselect]

Re: hwsiii---Need proping advice

Sorry about that, now I am having second thoughts on whether I should get a ss prop or not. The only thing I use the boat for is fishing and I spend a lot of time in the shallows. I try to troll out to deeper water before firing up the outboard, but you never know whats underneath sometimes. I am just thinking that aluminum is a little more forgiving if something should happen. Im torn on this.

 

[walleyehed]

Re: hwsiii---Need proping advice

You'll pay for a stainless (which the hub is more forgiving in a blade-strike) with the savings of not having to repair the aluminum which also wears MUCH faster. I want to talk with hwsiii then I'll post back.

 

[Proselect]

Re: hwsiii---Need proping advice

I guess I didn't think of a stainless with a hub that was forgiving. So what stainless prop does this come down to? PM me if you don't want to post over the board. I would like to check it out and start puting money away for it.

 

[walleyehed]

Re: hwsiii---Need proping advice

OK, here's what I've pinned down.
#1, you give GPS speed-FACT
#2, Your engine gear ratio is 2:1-FACT
#3, Your prop is a known 17P-FACT
#4, I am figuring a realistic 14% slip for that aluminum Prop.
This leads to only 1 conclusion and that targets your tach as being approx. 700 RPM LOW at WOT.
Your true RPM is close to 5850-5900 actual to achieve 41.8mph with that particular 17P aluminum.
I'm sinking my thoughts (and a good weeks wages) into saying the tach is bad.
I used to run a 17 and an 18P on my 115 rude on my 18'6" Supersport-about 800lbs heavier than yours and still ran 5800 with the 18P at close to 42mph. A tach change would give us true numbers and we can figure out how to deal with the prop and set-up of the engine mounting when we get 100% accurate rpm numbers.

 

[Proselect]

Re: hwsiii---Need proping advice

That does make some sense. What sucks is the tach is brand new. I don't doubt the possibility that it may be off though. Is is possible the dial on the back of the tach is not set right? Maybe its not on the right setting, I didn't look. I bought the boat with the new guages in it.

 

[Proselect]

Re: hwsiii---Need proping advice

I did some searching and it shows by teleflex that my setting should be 6p and that is what its at. Boy that sucks if a brand new tach is garbage already. I do have a digital multimeter capable of reading rpm. I will have to see if its possible to hook up to the tach wires somehow and see if I can compare it. I don't want to go and spend 60 bucks on a new tach just to see if this one is accurate or not.

 

[walleyehed]

Re: hwsiii---Need proping advice

If your gps is showing 41.8 and the prop IS a 17P, I already know the gear ratio so that leads directly to the tach. In theory, a 19P SS such as a Stiletto would be pulling "close" to what your tach is telling you. If the prop you're running is NOT a 19-20P, then the tach is off-not uncommon...especially if it is a teleflex.

Wires to tach should be: Grey is signal, Purple is power (12+) bottom center term. should be Gnd., and top off-set is power for light.