Prop results for hwsiii and others

[dazk14]

Hi fellas,

Any help here would be appreciated.

1 Year, make and model of boat
1986 Sun Runner 220 SB (Sunbridge/aft cabin)

2. Length, width and base weight of boat, look for boat decal on back of boat
Hull length 20?6? , max beam 8?6? base weight #3500 for v-8 I believe (Mine is VP 4-cylinder)

2a.What is the maximum recommended HP for your boat
It?s an I/O, but I did have the boat before with a 305V-8 (did around 40mph)

3. Number of people and gallons of gas normally on boat
2@200 plus 40 gallons gas, 20 gallons water, 2 batteries

4. What do you use the boat for
Cruising east coast/ Boston Harbor 1-3ft waves

5. Is it a Deep Vee and if so how many degrees of deadrise
Not sure, I?m guessing 17 deg(not the deepest I?ve seen)

6. Year, make. manufacturer and model of motor
1986 Volvo Penta AQ 151 290 single prop left hand outdrive

7. HP and gear ratio of motor IMPORTANT
145HP at motor at 5500rpm 2.15:1 gear ratio

8. Manufacturer?s recommended Wide Open Throttle (WOT) range
4800-5500

9. Anti-ventilation Plate height above keel of boat.
N/A Volvo AQ series 290 I/O

10. Is it a bass boat or does it have a pad bottom
No pad

11. Does it have a hydrafoil, dolefin or trim tabs
Yes, doelfin. It uses a special doelfin Volvo adapter plate, so it?s pretty wide. I added it and it does help getting on plane, maintaining plane in rough seas, etc.. I would consider removing it.

12. Make, model, diameter, pitch, number of blades and whether SS or aluminum prop
Michigan wheel 082(0)91 short hub, ??16dia., 15pitch, 3 blade elephant ear, aluminum. Note- I cannot read the 3rd from last digit. From research, it seems to be a 16x15, but it only appears to be 15"dia arhhh. I recall it being 15" pitch. Sorry for torturing you here!

13. WOT RPM and speed
RPM _5200_____ Speed _22.5_____ GPS __yes____ No. of people _2_____ Gal. Gas __40______

NOTE: Power trim does not work(and won?t be fixed $oon), so motor always lives in the lowest possible trim spot(tucked under). For the type of cruising I do, it doesn?t seem to hurt much. With the usual chop, I?m satisfied when I can pull the trim tabs up.

14. Sea Level

15. Yes, but did valve job over winter. Comp reading were 170psi, I expect they?ll be closer to 200psi now

16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
2 seasons with the "16x15" and always felt it was so,so. Boat formally had a Michigan SMC 340 15 X 15 cupped (obvious rework from my eyes)elephant ear did ~25mph at 5500rpm max 1 person-I recall PO saying it was 17"pitch. Prop got damaged and had so-so planning with loaded boat.

17. Does the prop show any damage that you can see
No

18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations
More top speed so cruising isn?t so high on Rpm, smooth running in choppy seas, minimize porpoising.
Planing at lower speeds would be helpful in rough seas and/or be fine for general cruising.

Note: The boat does have Bennett trim tabs.

19. I have no way at this point to test, so I?ll live with whatever I get and go from there.

Please note* I just ordered from iboats an Amita 4 long hub 14.75"dia by 15"Pitch ($98 delivered, so it seems worth a shot). It?s a PIA to change props once it?s in, so it?s worth it to me to toss on now - what seems to make sense and go from there.

Do you think this makes sense and I have no problem buying another prop if needed - before or after launching. Stainless steel is fine if that makes the most sense.

REMEMBER, The numbers I give you will be NO better than the information you give me (I know that what worries me!) Really, with the iboats price on Solas props - there's little downside.

Sorry about the somewhat vague data with the props, just trying to get into the hunt here.

The only thing I ask of you is to come back and give me a report of WOT RPM and speed for my database.

It?ll be my pleasure!
Thanks a ton,
Mike D

 

[dazk14]

Re: Prop results for hwsiii and others

Just figured out the "Edit" function so I fixed my above glitches.

Thanks!

 

[hwsiii]

Re: Prop results for hwsiii and others

Mike, a major problem you have is the outdrive not being able to trim up, as that will not allow you to raise the bow and thus you have a lot of hull friction that slows the boat down. With the outdrive tucked up under the boat it is also bad because it is steadily pushing the bow down and the prop is not running at anywhere near its optimum angle of attack for maximum performance.

NOTE: Power trim does not work(and won?t be fixed $oon), so motor always lives in the lowest possible trim spot(tucked under). For the type of cruising I do, it doesn?t seem to hurt much. With the usual chop, I?m satisfied when I can pull the trim tabs up.

I am sorry I cannot tell you what performance to expect out of the Amita prop under the conditions you will be running it with. I am also sorry to say it, but for maximum performance you will need to fix the outdrive so you can adjust it to where it will raise the bow and thus create less wetted surface area.

I did check your prop for you, and you do have the right numbers and it is a 16" x 15" pitch MW Left hand prop, hope you remembered to order a left hand prop as well.LOL

I can tell you that right now your prop slip is right at 35%, and that is exceedingly high. Theoretically the Amita ought to bring that down, but I am not positive it will do much under these circumstances. And in most cases I would recommend you getting rid of the hydrafoil, but I am not positive in this case, although theoretically anytime they cannot run on top of the the water, at high speeds and if it is tucked under the boat at an angle it will essentially create a lot of extra unneeded friction and drag.

Prop Slip

For you to get anymore real performance out of your boat you will have to fix the power trim on the outdrive.

I am Sorry, I have to tell you this Mike.

But, I believe that if you fix the outdrive you should be able to get about 28 MPH out of your setup.


H

 

[dazk14]

Re: Prop results for hwsiii and others

Thanks H!

Yeah, I realize mine is a bit of an odd ball.

Have you seen the geometry of the Amita 4 compared to a run of the mill VP elephant ear. I did recheck the diameter of my old prop and it's only 15" by my eyes. So let's compare the different characteristics of a 15X15 elephant ear vs, the 14.75 x 15 Amita 4.

Do you think the Amita 4 will give me enough stern lift and limit porpoising to remove the doelfin? I can always put it back on...

I can say, I did remove the fin on the back of my Regal 2100 when I switched to a 4 blade Stilletto(from 3 blade mercruiser alum) and it worked out fine. I had installed the fin originally to allow for the slowest planing speed pulling little kids on a tube.

I probably shouldn't be such a chickin' about removing the fin, after all I do have trim tabs!

Thanks again!
Mike D.

 

[hwsiii]

Re: Prop results for hwsiii and others

It will give plenty of stern lift, but porpoising you never can tell about, there are so many reasons a boat can porpoise. Try it without the fin.



H

 

[dazk14]

Re: Prop results for hwsiii and others

Thanks H. I greatly appreciate your thoughts!

I have attempted to attach pics of the VP(Michigans) props I have used in past sitting next to the Amita 4.

What are your thoughts on the rake of the amita vs. VP's and also do you think there's enough blade area on the amita.

Do you think the amita will likely give more stern lift than the elephant ears. The Amita certainly is a much more sophisticated prop from a blade geometry point of view.

Sorry about all the questions, just trying to get my arms around this. I have read all your white pages and they're great.

If anyone else has had experiences pushing a barge, please feel free to chime in.

Thanks again,
Mike

 

[hwsiii]

Re: Prop results for hwsiii and others

Mike, like you said, the Amita has much more blade geometry than the older elephant ears. And yes you are pushing a barge, LOL, but I believe you will do much better with the Amita.

BUT in order to really get some speed you are going to have to fix the power trim unit.



H