Boat props x2 Help would be great!

[tmartin]

I have a 99 Seaswirl Striper Wa with a factory Gil Bracket. On that bracket are two 2008 Honda BF150's. I am looking into a prop that has been reccommended.. 4-blade 14-5/8 x 16 Stainless

Would this work? What do you reccommend?

1) Performance issue you are trying to correct.
40mph max speed, cruise at 25mph.

2) Current prop manufacturer, model, aluminum or stainless and as a minimum.
Honda aluminum

3) Current prop diameter and pitch (required).
15.25 x 15 aluminum 3-blade ONE IS COUNTER ROTATING

4) Wide open throttle RPM and speed with an average load (very helpful)
hitting 6400rpms VERY easy.

5) Engine/drive make, model, year, and HP
2008-Honda BF150 x 2

6) Boat make model, year, length and weight
1999 Seaswirl Striper Walkaround, 6,000lbs


1. Year, make and model of boat
99 seaswirl striper 2600wa HT with factory Gil bracket

2. Length, width and base weight of boat, look for boat decal on back of boat
24ft, 102", 4000lb without motor, 5000lb with motors

2a.What is the maximum recommended HP for your boat
300hp

3. Number of people and gallons of gas normally on boat
2-3 adults...134 gallons of gas


4. What do you use the boat for
100% - fishing


5. Is it a Deep Vee and if so how many degrees of Deadrise
20 degrees deadrise

6. Year, manufacturer and model of motor
2008 Hoinda BF150 x 2 ONE IS COUNTER ROTATING

7. HP and gear ratio of motor IMPORTANT
150hp, 2:14 Gear Ratio x 2

8. Manufacturer?s recommended Wide Open Throttle (WOT) range
5500 RPM is at rated 150hp

9. Anti-ventilation Plate height above the bottom of the transom of boat if it is an outboard in inches, use a straight edge or a board under the keel and sticking out to the anti ventilation plate for a reference, and take about 4 pictures for us to see.

4" above

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

11. Does it have a hydrafoil, dolefin or trim tabs
will have trim tabs--not currently

12. Manufacturer, model, diameter, pitch, number of blades and whether SS or aluminum props.
IMPORTANT
Honda, 15.5? diameter, 15 pitch, 3 blades, aluminium

13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. Make sure you trim the prop up until it starts ventilating and then just trim in until it quits ventilating. If you do not have a tach you can buy a Tiny Tach for less than $ 50
RPM ___________ Speed (GPS)___________ No. of people ____________ Gal. Gas ________

WOT 6400rpm @ 35.5mph, 1 people, 134 gallons

14. Are you at sea level or a higher elevation, give us the elevation in feet __________

sea level

15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way by only using the control on the console, checked compression, looked at the plugs and checked spark, is the bottom of the boat clean and barnacle free, and have you checked the Tachometer against a mechanics tach, all of the foregoing could be the reason your prop is not attaining full RPM.

Everything ok.

16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop.

Came with boat, unknown history, hits 6400 EASY!!!! (motors at 28hrs each)

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

I want low end torque (hole shot) and good fuel economy. @ Say 3800 RPMs?

 

[steelespike]

Re: Boat props x2 Help would be great!

I'm a little outside of the experts but from my experience.
If you are trying to reach the rpm at rated hp I don't think a 4 blade 16 will do it.
I don't know the rpm range of your motors But typically outboards seem to run about 500 above the rpm at rated hp. Rule of thumb 1" in pitch will chage rpm APPROXIMATELY 200 rpm.Adding a blade usually reduces rpm by ABOUT 100.
It would seem the 4 blade 16 will put you at ABOUT 6,100.If your looking for the 6,000 area your close and it may turn out to be perfect. If your looking for 5,500
it doesn't appear to be even close.A 4 bladse should improve hole shot and low to mid range performance.

 

[hwsiii]

Re: Boat props x2 Help would be great!

T, after running some preliminary numbers I show that your speed is a lot slower than what you should be getting, as usually a bracket can increase speed a little and I show you should be doing better than 45 MPH.

You did a superb job on filling out the form and I just need to verify some information.

I have a 99 Seaswirl Striper Wa with a factory Gil Bracket. On that bracket are two 2008 Honda BF150's.

1.How far does the bracket extend from the transom.

I am looking into a prop that has been reccommended. 4-blade 14-5/8 x 16 Stainless

2. EXACTLY what manufacturer and MODEL of prop is recommended and who is recommending this prop, because I show you should be running a higher pitch prop than that.

1) Performance issue you are trying to correct.
40 mph max speed, cruise at 25mph.

4) Wide open throttle RPM and speed with an average load (very helpful) hitting 6400rpms VERY easy.

When you trim the motors up is this the maximum RPM you can turn with the motor.

WOT 6400rpm @ 35.5mph, 1 people, 134 gallons

3. In one place you say the boat does 40 MPH and then you you say at 6,400 RPM you are only doing 35.5 MPH and I don't understand why.

8. Manufacturer?s recommended Wide Open Throttle (WOT) range
5500 RPM is at rated 150hp

4. I also find your motors recommended RPM should be between 5,000 and 6,000, please verify this.

9. Anti-ventilation Plate height above the bottom of the transom of boat if it is an outboard in inches, use a straight edge or a board under the keel and sticking out to the anti ventilation plate for a reference, and take about 4 pictures for us to see.

4" above

5. From the speeds I am seeing it makes me think that the engines are not mounted high enough on the bracket, but 4" should be high enough, depending on the bracket length from the transom. Please lower the engines so the anti ventilation plates are parallel with the bottom of the boat and lay a straight edge on the bottom of the keel sticking out to the anti ventilation plate and measure this distance. And please take a few pictures so I an see the bracket and the height of the motors from the keel.

I do not believe a 16" pitch prop is enough pitch for your boat and motors and you should be getting much more speed than you are at this time. I just need a little more information to solidify my calculations.
This is the all up weight that I think you ran your speed test with, please check this and see if it is about right.

Boat and Motor

You also might try reading this for a better understanding of changing props for better performance.

http://forums.iboats.com/showthread.php?t=365653



H

 

[tmartin]

Re: Boat props x2 Help would be great!

The boat's LOA 25.6' seaswirl striper model 2600WA. But in the water it's like 24'. (bow pulpit is 1.6')

The max speed I'm currently getting is almost 36mph (GPS) @6400rpms.. Sorry for the 40mph thing...

Power band for a BF150 really is exactly 5500 for 150hp. After that it goes up a little to 160'ish @ 6000rps.. BUT YOU ARE CORRECT--it's 5500-6000 max motor rpm range.

Low Power for me is darn important. Crossing our Bars (ocean) are dangerous. So, low end speed is a lifesaver. I don't mind hitting nearly 6k, just thought 36mph top end was rediculous.

Bracket extends 27"

Motor cavitation plate is 4.4" ABOVE the bottom of the hull's Vee. I can move it down 1" or up 3".....that's it either way...

Trimminmg motor up to best least resistance without cavitation, max RPM's is 6400.

Motors down, max RPM's is 6100rpmns.

The weight, your close the way you have it. I do have 4 batts and maybe 50 more pounds of "stuff". But listen, I fish with 1500 lbs of Ice and Tuna...THATS why I want low-end torque...

 

[junior1113]

Re: Boat props x2 Help would be great!

with all that weight i like the idea of 4x16's should bring u down 500. you should pick up speed with less slip. all i run is 4 blade. great hole shots. better mid range fuel econ. better for trolling. and slower on plane speed with great torque. great for fighting rough waters. my 2 cent

 

[hwsiii]

Re: Boat props x2 Help would be great!

T, I am sorry I have been with the grand kids and haven't had time to get back with you, but I will work on it tonight.



H

 

[tmartin]

Re: Boat props x2 Help would be great!

You just take your time! For what you do, I am happy to wait...

 

[hwsiii]

Re: Boat props x2 Help would be great!

T, when I run my numbers they just DON'T match any of the numbers you have with your tests. I just need to know do your motors have an automatic cutout when your motor reaches 6,400 RPM, if that is true then I can understand the anomaly.

Prop Piker

You can see from my calculations above that I show your boat should be doing about 48 MPH. Then if you look at the Prop Slip, you will see that to even do 46 MPH with a 19" pitch prop with a 9% prop slip requires 6,000 RPM, and if you can only turn 6,400 RPM with a 15" pitch then theoretically you will never be able to reach 6,000 RPM with a 19" pitch, unless your motor has an automatic cutoff at 6,400, thus my statement that it has to have the cutoff.
Please verify this for me.


Prop Slip

H

 

[tmartin]

Re: Boat props x2 Help would be great!

Funny you mention the 6400rpm thing. I would have to say yes that they have a rpm cap. That rpm is quite easily achieved.

If everything I've said is true and accurate, that would mean the only thing that's off would be the mounting...

Slipage maybe? Do I have to now be concerned that my motors are mounted to high? What do you think?

27" aft of transom and 4.5" above bottom of hull. Is that OK?

 

[Texasmark]

Re: Boat props x2 Help would be great!

T, after running some preliminary numbers I show that your speed is a lot slower than what you should be getting, as usually a bracket can increase speed a little and I show you should be doing better than 45 MPH.

You did a superb job on filling out the form and I just need to verify some information.



1.How far does the bracket extend from the transom.



2. EXACTLY what manufacturer and MODEL of prop is recommended and who is recommending this prop, because I show you should be running a higher pitch prop than that.





When you trim the motors up is this the maximum RPM you can turn with the motor.



3. In one place you say the boat does 40 MPH and then you you say at 6,400 RPM you are only doing 35.5 MPH and I don't understand why.



4. I also find your motors recommended RPM should be between 5,000 and 6,000, please verify this.



5. From the speeds I am seeing it makes me think that the engines are not mounted high enough on the bracket, but 4" should be high enough, depending on the bracket length from the transom. Please lower the engines so the anti ventilation plates are parallel with the bottom of the boat and lay a straight edge on the bottom of the keel sticking out to the anti ventilation plate and measure this distance. And please take a few pictures so I an see the bracket and the height of the motors from the keel.

I do not believe a 16" pitch prop is enough pitch for your boat and motors and you should be getting much more speed than you are at this time. I just need a little more information to solidify my calculations.
This is the all up weight that I think you ran your speed test with, please check this and see if it is about right.

Boat and Motor

You also might try reading this for a better understanding of changing props for better performance.

http://forums.iboats.com/showthread.php?t=365653



H

Just love it man. Can't argue with the data and you can produce it. Way to go.

Best Regards,
Mark

 

[hwsiii]

Re: Boat props x2 Help would be great!

Mark, thank you very much, I have a workbook that has now become many pages with all of my different calculations and data analysis spreadsheets to try and resolve any particular boat and motor combination and its potential speeds.

T, I have not dealt with a tremendous amount of setbacks in the past, I do remember a couple of things about them though. If I remember correctly, for about every 12" of setback you can raise the motor up about 1" or more extra for each 12" added setback. And I am pretty sure the height of the motor is also dependent on the speed as well, one you get past about 35 MPH. I don't think you are too high at this time, but you might want to install a water pressure gauge to be positive you have enough water pressure to keep the motors from running too hot. The guideline I ALWAYS use for motors is that when you are at cruising speeds and higher you should be seeing the water just splashing over the top of the anti ventilation plate, and you should be able to see the anti ventilation plate quite clearly.

Theoretically speaking the props you have now probably are not designed for running that high in the water column, and could be having ventilation problems. But also speaking theoretically that would make the props turn faster with higher prop slip, and I do show your prop slip at this time to be 18%, and on boats like yours I recommend changing the props out when you reach 15% prop slip for props that will reduce your prop slip closer to about 8%. And if you could turn those props 6,400 RPM with 8% prop slip you would be doing 39 instead of 35 MPH. So at this point I wouldn't lower the engines because you are going to change props anyway, and the new props will work much better at height than what you have now.

It sure would be nice if Dale or Kenny see this thread and chime in with their vast knowledge on this, because I know they are a lot more well versed in this than I am.

T, if you would call the Honda dealer Monday and VERIFY that these motors cutoff at 6,400 RPM then we can continue with our new prop selection. Right now I am not POSITIVE my calculations are right, because you are only able to turn 6,400 RPM with the 15" props, I would much rather err on the side of caution than just play like I am right and continue. I am NEVER wrong, UNLESS I am breathing.


H

 

[hwsiii]

Re: Boat props x2 Help would be great!

T, from reading your posts you don't need low end thrust it is required or it can put you in a life threatening situation. Between the ocean bar and the extra 1,500 pounds of fish and ice you have at times (that is almost a 30% increase in weight at any point in time), and still trying to maintain a respectable speed getting to the fishing grounds and yet still have maximum thrust available for steep seas when crossing an ocean bar so you have control of your speed enough to stop a pitch pole situation or a following sea that collapses into the boat and fills it with water is imperative.

That is why I feel I have to have all the information I can get, and to know it is right.

We have a bar like that at Dog Keys Pass, and when the tide and wind and wind direction all coincide just right we have had many people DIE at that pass. That is why I take this so seriously and ask so many questions.

Low Power for me is darn important. Crossing our Bars (ocean) are dangerous. So, low end speed is a lifesaver. I don't mind hitting nearly 6k, just thought 36mph top end was rediculous.

The weight, your close the way you have it. I do have 4 batts and maybe 50 more pounds of "stuff". But listen, I fish with 1500 lbs of Ice and Tuna...THATS why I want low-end torque...

H

 

[tmartin]

Re: Boat props x2 Help would be great!

I really appreciate your knowledge too!

I have made a few calls and am awaiting some additional info. Finding the Honda height requirements to mount engines is like pulling teeth. Man, I sure wish I could get an answer...

You have me scrutinizing the input data that I gave you. I know the hull in water lenth is actully 24 not 23'. And it's possible the speed was 37.5 not 35. But I am sure about the 6400rpms part.

Other than that, I too am at a loss.

But listen, don't you even think I don't appreciate your knowledge!

We will figure this out.

Thanks for understanding my healthy fear of poor water condition navigation...

TJ

 

[hwsiii]

Re: Boat props x2 Help would be great!

T, this was just last year, and Steven Bond a police officer on the Ocean Springs Police department was eventually found dead about a week later. They were just trying to cross the bar to get inside the island and be protected from the heavy seas in the Gulf.


Survivor of capsized boat: 'I had hold of Whitney and I wasn't letting go'
By Paul Cloos
May 19, 2009, 4:00PM
(Press-Register/Cherie Ward)Jackson County, Miss., Sheriff Mike Byrd, center, looks through the contents of a boat discovered capsized Monday morning while officers secure the vessel. Four of the 5 passengers have been rescued.

Jonathan Navas said today that he was prepared to drown rather than face another night drifting aimlessly in the Gulf of Mexico.

"I had a hold of Whitney and I wasn't letting go," Navas, 23, said of his bride. "She had my pocket and wasn't letting go, but it was so horrible out there -- being smacked around by the rough water -- that we talked about just taking off our lifejackets and drowning instead of spending one more night out there."
Jonathan Navas, rescued after boat capsized in the Gulf of Mexico
Whitney Navas, held tight to her husband's pocket to avoid drowning in the Gulf of Mexico.

Luckily, Navas and his wife of only one month, Whitney, along with Michael Green, 31 and Becky Welch, 37, were plucked from the water by a Coast Guard helicopter crew about 1 p.m. Monday. Navas said they spent about 24 hours floating as far as 15 miles out in the Gulf of Mexico.

A search for Stephen Bond, 32, a passenger on Navas' boat and an Ocean Springs, Miss., police officer, was still under way this afternoon.

Navas' 21-foot recreational craft capsized in Dog Keys Pass just off of Horn Island Sunday afternoon only moments after a powerful thunderstorm dumped heavy rain and produced large swells, he said.

Steven Bond, Ocean Springs, Miss., police officer remains missing after boat capsized Sunday in the Gulf of Mexico

The group had been to the island earlier Sunday and a search and rescue mission was launched at midnight.

Navas said while in the water Sunday night he and his wife saw flashes of light dancing on the water from nearby search boats.

"We hollered and hollered," Navas said. "But, they could not hear us over the wind and it was too dark."

Green and Welch were rescued first with the Navases shortly after, Navas said. All four were taken to Gulfport Memorial Hospital and were slated for release this afternoon, he added.

"I had no idea where in the water we were," Navas said. "We prayed a lot, but we got to the pointed that we didn't think we'd make it. We promised that if we did, we'd appreciate life more. "

Twenty boaters along the Mississippi Gulf Coast had to be rescued from vessels caught in treacherous waters Sunday night, said Casey Ranel of the New Orleans Coast Guard.

 

[tmartin]

Re: Boat props x2 Help would be great!

Absolutely chilling!

Did I mention I was an ex-Coastie...saw enough to change me forever. Now I respect the ocean.

Thanks for the reminder.

 

[hwsiii]

Re: Boat props x2 Help would be great!

I have had boats all of my life and love the Gulf. I got my 100 Ton Masters Ticket at 19 years old and ran my first charter boat, that was a 65 footer. I have been caught in over eighteen foot seas in a 23' Sportcraft in over 75 MPH winds one time, and I have learned to have great respect for the water and weather.

The only thing that really matters to me at this point, is if the motors have a cutout at 6,400 RPM. If that is true then it tells me you that you need a larger pitch prop than what would be considered normal if your motor just couldn't turn any more RPM with that prop, instead of the motor actually stopping it from getting higher RPM. My numbers say that the motor override is actually stopping the motor from turning any more RPM than that.


H

 

[Texasmark]

Re: Boat props x2 Help would be great!

On the Horn Island tragedies/potential tragedies, Horn Island is not like the mouth of the Canadian river in the NW USA. It's part of a string of barrier islands on the US Gulf coast about 10 miles offshore, no big raging currents and tides. It's a pretty docile place most of the time; course in a storm, all bets are off. Easy to get lulled into complacency when things are normal and get smacked when you least expect it. I am amazed at capsizing a 21 footer.

I have fished those islands many times with a 14'; but I fished daylight only and kept an eye peeled for storms, squalls and the like. I did get caught out in a squall once and tucked around the back side of Cat island and waited the rain out.

Mark

 

[hwsiii]

Re: Boat props x2 Help would be great!

Mark, I had some friends out in a 21' Wellcraft many years ago that were out fishing the rigs and the weather got bad, so they tried to outrun the storm, and when they got to Dog Keys Pass they weren't able to handle the seas and three of them didn't make it back. I will never forget that, and I am sure that, coupled with a few other friends over the years having close calls in storms in that particular pass is why I think of it as the most dangerous place in our area.

I thought what T was talking about was kind of like the Columbia River in Washington, and I have seen a few films of that, and that is one dangerous place a lot of the time it appears.

Dog Keys Pass

H

 

[Texasmark]

Re: Boat props x2 Help would be great!

hwsiii,

I was going to move this conversation over to the boating forum but you might not catch it so I will see if the moderators will let me sneak it in here.

On Dog Keys Pass, your picture and the current Google satellite image of what appears to be the pass are different. Apparently one of the hurricanes rearranged things there, like I don't even see a pass. Looks like a hurricane added to the W end of Horn rather than remove things which is usually the case....like Chandelier Island......what's left of it. But I did notice that the waves in my satellite pic. were beaching from the South and West simultaneously on the West end of Horn Island which kind of gives me and idea as to what could happen in a storm.

Also, the pic of the pass you showed indicated to me a lot of shallow water through the Southern end of it and I can see where that would be surely hazardous. I never made it over to horn from Gulfport. Primarily Cat and sometimes Ship.

Mark

 

[hwsiii]

Re: Boat props x2 Help would be great!

T, where are you, I need to know the rev limiter setting for your motor. LOL


Mark, that bar was always the problem, and when you combine it with seas from different directions and a bad tide, at times it was very treacherous. I was caught there once by myself when I was about 15, and there was a small storm, so yes I had GREAT respect for it. I haven't gone to that end of the island for a long time, I didn't even know it was changed.



H