ox66 prop question

[J.B.]

my 1998 ox66 250's are burning 29 GPH @4000 RPM while pushing my 26' Salt Shaker 30 MPH. I'm running 3 blade Ballistic props and am wondering if changing to a better quality 4 blade prop will increase my fuel economy.

 

[hwsiii]

Re: ox66 prop question

JB, welcome to Iboats prop forum and we will try to help you as much as we can but without more information no one can help you, and I will tell you I need more information than anyone else. But if you would like my help fill this form out and I will help you as much as I can, if you would prefer to not go to this much trouble there are other people who will help you.

Iboats Boat and Motor Info
1. Year, make and model of boat
2. Length, width and base weight of boat, look for boat decal on back of boat
2a.What is the recommended HP for your boat
3. Number of people and gallons of gas normally on boat
4. What do you use the boat for
5. Is it a Deep Vee and if so how many degrees of deadrise
6. Year, make. manufacturer and model of motor
7. HP and gear ratio of motor IMPORTANT
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape across the prop and the lower unit and then cut it between the prop and the housing and turn the motor until the tape lines up with each other, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
10. Is it a bass boat or does it have a pad bottom
11. Does it have a hydrafoil, dolefin or trim tabs
12. Make, model, diameter, pitch and whether SS or aluminum prop
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. If you do not have a tach you can buy a Tiny Tach for $ 50
14. Are you at sea level or a higher elevation, give us the elevation in feet
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
17. Does the prop show any damage that you can see
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
19. If you are trying to attain a better cruising speed and fuel savings or trying to attain a faster speed I will want you to take your boat and run it with 1 or 2 people and give me the RPM and speed readings starting at 3,000 RPM in 500 RPM increments all the way to WOT.

REMEMBER, The numbers I give you will be NO better than the information you give me

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


H

 

[hwsiii]

Re: ox66 prop question

Thanks for replying to my post. I'll do my best to answer your questions, however I'm finding it difficult to get much information on my boat. It's a 26' Salt Shaker made in Punta Gorda FL. Basically a custom made vessel and very few were made. I've been told that the Dep Vee hull is based on an Ablemarine design.

1. 1998 Salt Shaker Custom
2. 26' 8.5' beam weight unknown
2a. Engines are original to the boat twin 250 HP
3. 2 people 125 gallons
4. fishing and cruising
5. Deep Vee dead rise unknown
6.1998 Yamaha OX 66 SWS
7 250 HP 1.81:1 ratio
8.5500
9.?
10.N/A
11 trim tabs
12.Ballastic SS with no visible markings. I'm having new hubs installed this week and should have pitch and diameter for you byb the end of the week.
13. 5300 RPM 3 peole 120 gallons of fuel GPs
14 sea level
15 recent tune up and compression (117-120 all cylinders)
16 Original equipment prop- poor fuel economy
17 no visible damage
18 I'd like to get better than 1 -1.2 MPG
19 I'll get these numbers for you after I get a new hub in one of the props

Thanks in advance for your assistance.

J.B

 

[hwsiii]

Re: ox66 prop question

JB, after running a preliminary analysis you ought to be able to get in the high 50's to low 60's with this setup and I was guessing a total allup weight of about 8,000 pounds.

H

 

[J.B.]

Re: ox66 prop question

H,
thanks for getting back to me. I think the weight figure you're using is 1000 - 1500 lbs light. I've got a call in to Salt Shaker for confirmation on this and dead rise figures. I';m still waiting for the prop dimensions from the shop and should have them shortly. I'm more concerned with fuel economy than top speed - I'd rather top out @50 and get better mileage, as I've gotten older I've lost some of " the need for speed"
Thanks again.

J.B.

 

[hwsiii]

Re: ox66 prop question

JB, I already answered this one but evidently it didn't get through for some reason. In your IM you said you were running Ballisti SS props, and in my opinion they are not very good props for your type of boat, as they usually have a lot of prop slip, although your boat has a very high HP to weight ratio and the rouh number is very high.
Without any numbers for speed and RPM I really don't know what props are best suited for your setup at this time, but if you use the boat in the oean or the Gulf it will theoretially be subjeted to formed seas and and wave ation that reates a lottt of extra drag at those times. The props you have now are not onduive to those kinds of extra loads. I believe the boat will run muh better with either a set of Rev 4's or Baypro 3's, but this is just a guess without having any data from the props you are already running. These props really like running high in the X dimension, whih helps with the drag reated from the lower units and they tend to hold the boat real well when you are running into head seas instead of ventilating from not having enough blade surfae area and lift.
I intend on helping you find the best props for your fuel eonomy and that is not normally what I do here, usually I just presribe muh better props for people than they have at the present beause it is a pain to prop a boat for the best possible intended uses and needs they have. I will be waiting for you to get the props bak on the boat and giving me the numbers I need for this analysis. Please use this form to fill out your test results and run the boat in reiproal diretions for testing, also if you normally run in formed seas try to do this in rougher water for more realisti results,instead of alm water. And do realize that we may have to run 2 to 3 other sets of props to find the best set for you, and I do have a plae that does this for a very inexpensive fee instead of having to buy props and then resell them at a large loss. Here is the form I would like you to fill out when you make the test runs.

Prop Test Results

 

[J.B.]

Re: ox66 prop question

Got the prop back on Sat. but family obligations kept me from testing. I should be able to take care of it today or tomorrow and have you the results by Wed.
Thanks again.

J.B.

 

[hwsiii]

Re: ox66 prop question

That sounds good JB,


H