Prop question - 1989 Sea Ray 300DA

[Grand Larsony]

Thinking about replacing \ upgrading the props on my 1989 Sea Ray 30' Sundancer with twin 5.7\260hp Mercruiser IOs.

I think I'm swinging 14x19 (factory standard) aluminums and am in correct RPM range right near 4,500.

Have heard that going to 4-blade 14x17 will help holeshot and economy without hurting top end much.

Anybody already done this? Got the part number(s) for props and any required hub or washer assemblies so I can check pricing online?

Many thanks !

 

[Grand Larsony]

Re: Prop question - 1989 Sea Ray 300DA

Holy cow -- I just stumbled on a few of the longer posts here... so, please, if it's ok, could I ask that replies be limited to those of you who have this boat & engine combo and have ACTUALLY made a change?

I just don't have the mental capacity to think through prop slip, theoretical top speeds, flux capacitor denegration values, etc.

My boat is pretty much ok as-is, but both props are dinged up a bit and I was hoping to replace them with something that gets me up quicker but does not reduce top-end speed too much. Frankly, if there is a fuel savings involved that would be great... but it's not that important to me.

 

[Bondo]

Re: Prop question - 1989 Sea Ray 300DA

Holy cow -- I just stumbled on a few of the longer posts here... so, please, if it's ok, could I ask that replies be limited to those of you who have this boat & engine combo and have ACTUALLY made a change?

I just don't have the mental capacity to think through prop slip, theoretical top speeds, flux capacitor denegration values, etc.

Ayuh,... There's a well defined process to come to the Correct answer...
But,...
You can wait for somebody with a boat Exactly like your's who's done the Exact same thing...
Just expect it to be a L o o o o o n g Wait...

Good Luck...

 

[45Auto]

Re: Prop question - 1989 Sea Ray 300DA

Have heard that going to 4-blade 14x17 will help holeshot and economy

I very seriously doubt if you'll be able to improve holeshot AND economy by going to a lower pitched prop, unless your boat was ridicuously overpropped to begin with. Since it was already propped very closely to optimum, you'll have to decide what you want most, economy or acceleration. Kind of like if you had to lock your car in one gear, and trying to decide between 2nd for acceleration or 5th for economy ....

 

[Grand Larsony]

Re: Prop question - 1989 Sea Ray 300DA

Great help guys, thanks... but, regardless of the lack of useful responses so far, I'm hopeful that a forum member with a 1980's SR 300DA 260hp Mercs has done this (or has tried). It's a very common boat.

 

[steelespike]

Re: Prop question - 1989 Sea Ray 300DA

Just to confirm your assumption.Yes "generally" a 4 blade will improve hole shot
and help stay on plane with less throttle.I do hope there is an identical boat
with your info.My memory isn't the best but I don't recall ever discussing a Sea Ray like yours for any reason.I've been hanging out here for a long time. If you will fill out the form at the top you might have your results later today and hwsiii usually hits it right on the nose.And he generally deals with a 4 blade solution.and states the detailed results expected and exact prop and those that report back have the exact results.Unfortunately it does require filling out the form. You don't have to understand anything or figure anything just answer the questions.

 

[Grand Larsony]

Re: Prop question - 1989 Sea Ray 300DA

If you will fill out the form at the top you might have your results later today

Thanks for the real help -- you mention a form, but I checked at the top of the props forum (the sticky area) and didn't see one. There is a checklist of items to provide, which I think I've done in my original question.

 

[45Auto]

Re: Prop question - 1989 Sea Ray 300DA

I have an 87' DA300 with twin 260's. However it had 17" pitch High Fives on it when I bought it so I have no basis for comparison.

You'd probably have better luck asking your specific question on the Club Sea Ray "Classic Cruisers" forum.

Don't be surprised when everyone that has changed props says that the new ones work better (doesn't matter whether they went higher or lower in pitch). They're all pretty much like you, nobody has fuel flow meters or any hard performance data on their old vs new prop. Since they just spent $500 or $600 on new props, they automatically "feel" that the new ones are better ......

 

[steelespike]

Re: Prop question - 1989 Sea Ray 300DA

If you will fill out the form at the top you might have your results later today

Thanks for the real help -- you mention a form, but I checked at the top of the props forum (the sticky area) and didn't see one. There is a checklist of items to provide, which I think I've done in my original question.

Sorry,See what happens when someone "assumes"I don't know where it is but hwsiii came up with it if you check his posts you will find it. Its pretty involved but very effective
for accurate prop selection.

 

[Grand Larsony]

Re: Prop question - 1989 Sea Ray 300DA

OK, I've tried to find the "form" and pulled these questions from a previous post... if HWSIII or someone else can make a recommendation I'd be most grateful.

1. Year, make and model of boat

1989 Sea Ray Sundancer 300

2. Length, width and base weight of boat, look for boat decal on back of boat

30' x 11'

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

Unknown - but I have twin 260hp Merc Alpha 1 outdriives

3. Number of people and gallons of gas normally on boat

4 adults, 140 gallons (full) and rarely less than 70 gallons (half). Typically I have half-to-three-quarters of gas and full water (40 gallons I think).

4. What do you use the boat for

Pleasure cruising

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

Deep vee

6. Year, manufacturer and model of motor

Original Mercruiser 260 hp 5.7 liter Alpha 1 outdrives

7. HP and gear ratio of outdrive IMPORTANT

Not known

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

4400 - 4600

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.

N\A - It's an IO

10. Is it a bass boat or does it have a pad bottom and is it on a bracket, if so how far does the bracket extend from the stern.

NO---NONE OF THE ABOVE

11. Does it have a hydrafoil, dolefin, whale tail or trim tabs and is the motor on a bracket, and if so how far back from the stern is the bracket

NO---NONE OF THE ABOVE

12. Manufacturer, model, diameter, pitch, number of blades and whether SS or aluminum props.
IMPORTANT

Original equipment Michigan Wheel aluminum 3 blade 17x19 no cup.

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 - 4500 max properly trimmed and with medium load (3-4 people, half tanks). Top speed = 40-42 mph GPS.

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

Lake Ontario

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.

Boat runs great - fully tuned & maintained. No issues. Not checked against mechanic tach, however.

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

Original equipment as far as I can tell. Some minor damage to blade tips, one or two blades may be very slightly bent. I'm looking for (in this order) better handling at the dock, improved performance getting on plane, improved fuel economy at cruise, slower minimum planing speed. I know I can't get them all.

17. Does the prop show any damage that you can see

Yes, see above.

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

See above.

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.

Can't do this until I'm in the water !

 

[steelespike]

Re: Prop question - 1989 Sea Ray 300DA

Good job, thanks for the effort I'll see if I can scare up hwsiii.
Unfortunately the gear ratio is critical,but maybe he has a reference.

 

[Bondo]

Re: Prop question - 1989 Sea Ray 300DA

7. HP and gear ratio of outdrive IMPORTANT

Not known

Ayuh,... It's 260hp times 2,+ 1.50:1 ratios...

 

[hwsiii]

Re: Prop question - 1989 Sea Ray 300DA

Grand, here are my preliminary numbers.

7. HP and gear ratio of outdrive IMPORTANT

Not known

I show the manufacturers recommended RPM to be between 4,200 and 4,600 RPM with a Gear Ratio of 1.32:1, please verify this.

Original equipment Michigan Wheel aluminum 3 blade 17x19 no cup.

I don?t know exactly what props you have on your boat, but I am positive they are not 17 X 19 with an alpha drive, and Michigan Wheel makes a lot of different models of props so I need to know exactly what size and pitch the prop you have now is as well as which model of props that are on it. If you will also take about 4 pictures at different angles of one of the props so I can see what the blade design is and get a feel for the blade surface area that will definitely help.

Original equipment as far as I can tell. Some minor damage to blade tips, one or two blades may be very slightly bent. I'm looking for (in this order) better handling at the dock, improved performance getting on plane, improved fuel economy at cruise, slower minimum planing speed. I know I can't get them all.

1. better handling at the dock I don?t know exactly what you mean by this?
2. improved performance getting on plane We can definitely do this
3. improved fuel economy at cruise Without a fuel flow meter no one can answer this question.
4. slower minimum planing speed We can definitely do this

Using the numbers that I found for you gear ratio and assuming that you are right about the 19? pitch of your prop I find your prop slip to be over 24% which is a little higher than what most of these heavy cruisers have with 3 blade props. By changing to the right 4 blade we will be able to lower that and also raise the boat higher out of the water for less drag and thus more speed and definitely a better ride.

After you get me the information and pictures of the props then I will have a better idea of what props better suit your boat.

If you will look at the prop slip it is at 24%, but the most important thing is that the Effective Prop Pitch is ONLY 12.7" of pitch when the actual prop is a 19" pitch.

Prop Slip

I found the total all up weight of your boat to be about 11,400 pounds, would you please check this and see if I am close.

Boat and Motor

H

 

[hwsiii]

Re: Prop question - 1989 Sea Ray 300DA

Bond-o, if you are sure that the gear ratio is 1.5:1 I need to change my prop slip numbers.



H

 

[Bondo]

Re: Prop question - 1989 Sea Ray 300DA

Bond-o, if you are sure that the gear ratio is 1.5:1 I need to change my prop slip numbers.
H

Ayuh,... Without counting teeth, or runinng serial #s,...
The 260hp of that vintage Will have a 1.50:1....

 

[QC]

Re: Prop question - 1989 Sea Ray 300DA

There was even a Sea Ray branded 5.7 in 1989 and it was also 1.5:1 . . . The 1.5 is somewhat "confirmed" by genuine Merc stuff I have. Even the 1988 models were 1.5 if this pair was built before the hull's year model.

Funny, but I found the 1:32 somewhere else that I use also. Where'd you find that hwsiii?

Also, I know that GrandLarsony asked that we keep this to his boat and prop only, but I think I can argue that this is about his boat . . .

hwsiii, what does your form do with horsepower? No, I am not trying to start that discussion . . . but, I am wondering how you account for crankshaft vs. propshaft horsepower as these were rated at the Crank. The propshaft rating change started in '90 and was complete in '91. They called 'em a 260/230 in '90 and a 230 in '91.

 

[hwsiii]

Re: Prop question - 1989 Sea Ray 300DA

QC, here are the answers, and I have talked with 45Auto about us having a new discussion, so everybody can hopefully learn new things.

Funny, but I found the 1:32 somewhere else that I use also. Where'd you find that hwsiii?

Marine Parts Plus

hwsiii, what does your form do with horsepower? No, I am not trying to start that discussion . . . but, I am wondering how you account for crankshaft vs. propshaft horsepower as these were rated at the Crank. The propshaft rating change started in '90 and was complete in '91. They called 'em a 260/230 in '90 and a 230 in '91.

For pre 1991 I use an 8% loss at the prop.

I actually use my base prop picker formula to get the correct pitch and diameter, and then I have other formulas that I use to fine tune the results, and then I use the same way everybody else does, just knowing what prop works better with which combination of boat and motor.

If you will notice though, at higher speeds the HP required to gain just a few miles and hour is massive. In this particular boat in order to gain just 3 MPH it requires a HP increase from 520 HP all the way to 600 HP, an increase of 80 HP just for 3 MPH, and we all know that just by changing to the BEST propeller we can gain that kind of increase in speed.

I hope that answers your question QC, and if anybody would like to discuss this, in a congenial fashion, I am very willing.



H

 

[Grand Larsony]

Re: Prop question - 1989 Sea Ray 300DA

Oh boy... this is why I LOVE THIS FORUM !!!

Found this from Sea Ray (factory prop specs, which I think I have):

1989 SR 300DA 2x260hp Alpha1: 1.50:1 ratio, 14x19 props, 4600 rpm

And, I'm ok with the weight estimate... we're usually pretty heavily loaded.

Does this help?

 

[Grand Larsony]

Re: Prop question - 1989 Sea Ray 300DA

And regarding my "expectations"...

1. better handling at the dock I don?t know exactly what you mean by this? -- I'd like better "bite" to help crab sideways and rotate the boat around the dock without having to throttle up too much. With I\Os I know this is never as good as Inboards, however.

2. improved performance getting on plane We can definitely do this -- This is a close second in my priorities. I usually tuck the drives all the way down, bottom out the trim tabs, throttle up to about 3/4+, get her up, reset tabs all the way up, trim outdrives, throttle back to 3,000 for a 30 knot cruise.

3. improved fuel economy at cruise Without a fuel flow meter no one can answer this question. --- Understood, and it's not that important.

4. slower minimum planing speed We can definitely do this -- Hope so. I currently need to run minimum about 2,7000 RPM at 25-27 knot cruise otherwise she falls off plane. If I deploy trim tabs and\or trim down the IOs I can hold plane at lower speeds (but with much more "drag").

So, with what I've given you... can you tell me if my dock mates are all wet?

They suggest 14x17 4-blade (possibly cupped) props for my boat.

Or was it 14.5x17 (I forget what's actuall available)?

 

[hwsiii]

Re: Prop question - 1989 Sea Ray 300DA

Grand,

I need to know exactly what the size and pitch the props you have now are as well as which model of props that are on it. If you will also take about 4 pictures at different angles of one of the props so I can see what the blade design is and get a feel for the blade surface area that will definitely help.

With this information, we can then pick a much better prop for your boat.

1. better handling at the dock I don?t know exactly what you mean by this? -- I'd like better "bite" to help crab sideways and rotate the boat around the dock without having to throttle up too much. With I\Os I know this is never as good as Inboards, however.

They will definitely have much more BITE at slow speeds, but, you also need to remember that there will also be an attendant speed increase at low RPM as well.

So, with what I've given you... can you tell me if my dock mates are all wet?

They suggest 14x17 4-blade (possibly cupped) props for my boat.

Or was it 14.5x17 (I forget what's actuall available)

And yes, with the information you have given me so far I agree a 17" pitch 4 blade is what you are looking for, we just need to pick the right one, and usually I would recommend a Solas Amita 4 blade aluminum in this case, but I need to see some pictures and I also need the model of the prop you now have, to be sure.



H