Bravo 3 Leg Prop Pitch

[businessjett]

Hello.

I'm the proud owner of a 2004 Sea Ray 260Da ( called a 275 here in Australia ).

It's only ever done 20knots at 4,000rpms. If I trim it will go 5,000 rpms.

I have had the engine and fuel system checked out and all that seems fine.

I am now wondering if my prop pitch is wrong. They have 18P stamped on them which I assume must be the pitch. ( see photo )

Would a larger pitch like 24 help it go faster ? The engine is a Merc 5.0.

Thank you,
Byron

 

[paulswagelock]

So, a larger pitch prop theoretically will push the boat further with each revolution meaning more speed. But, that is very dependent on hull type, condition, and engine. I would expect a Merc 5.0 on that size boat borders on being a little underpowered. Your max rpm is close to what it should be. Moving up in pitch will likely be too much for that motor in your boat, resulting in low max rpm, slow takeoff, and slower top speed. You might be able to spin a 19 or 20 pitch, but that will be trial and error. A 4x4 prop set up might help you out a bit, probably in an 18 pitch.
In the picture your bottom looks fouled which would impact performance as well.

 

[Scott215]

I would try 19 pitch and see, make sure the hull is spotless on bottom and side

 

[Stray Current]

What’s your rpm at wot?

 

[businessjett]

So, a larger pitch prop theoretically will push the boat further with each revolution meaning more speed. But, that is very dependent on hull type, condition, and engine. I would expect a Merc 5.0 on that size boat borders on being a little underpowered. Your max rpm is close to what it should be. Moving up in pitch will likely be too much for that motor in your boat, resulting in low max rpm, slow takeoff, and slower top speed. You might be able to spin a 19 or 20 pitch, but that will be trial and error. A 4x4 prop set up might help you out a bit, probably in an 18 pitch.
In the picture your bottom looks fouled which would impact performance as well.

Thank you for your reply.

In the sea ray web site I found the stats on what prop they supplied with the boat new

16 X20 CUP SS LH


14-3/8 X 20 CUP SS RH

My is 18 P so seems at some stage it’s been changed

 

[businessjett]

What’s your rpm at wot?

Thanks for the reply.

It’s 4,000rpm. I can get it to 5,000 rpm by trimming the leg .

Top speed is 20knots which ai have read is low .

Plus I found on the sea ray website the boat comes with these

16 X20 CUP SS LH


14-3/8 X 20 CUP SS RH

Mine is 18p so someone must have changed it.

I’m wondering if I went back to the sea ray specs if the top speed and time to get on the plane would improve ?

 

[businessjett]

I would try 19 pitch and see, make sure the hull is spotless on bottom and side

If I buy 19 . Do prop shops allow you to return them ? I suppose that’s a question for me to ask the actual shop I buy them from

 

[businessjett]

So, a larger pitch prop theoretically will push the boat further with each revolution meaning more speed. But, that is very dependent on hull type, condition, and engine. I would expect a Merc 5.0 on that size boat borders on being a little underpowered. Your max rpm is close to what it should be. Moving up in pitch will likely be too much for that motor in your boat, resulting in low max rpm, slow takeoff, and slower top speed. You might be able to spin a 19 or 20 pitch, but that will be trial and error. A 4x4 prop set up might help you out a bit, probably in an 18 pitch.
In the picture your bottom looks fouled which would impact performance as well.

Thanks for the reply.

I found on the sea ray site the boat came with these props so someone must have changed them at some stage .

Do you think if I went back to the recommended ones I would get on the plane faster and a better top speed ?

16 X20 CUP SS LH


14-3/8 X 20 CUP SS RH

 

[skibum]

Do you know what the ratio of drive you have is, and if it is the same as what the boat was sold with?

I'm just thinking out loud here, but since the props are different than what the boat was sold with, you should probably verify that the drive ratio has not changed as well.

 

[Maggieiscrazy]

Thanks for the reply.

It’s 4,000rpm. I can get it to 5,000 rpm by trimming the leg .

Top speed is 20knots which ai have read is low .

Plus I found on the sea ray website the boat comes with these

16 X20 CUP SS LH


14-3/8 X 20 CUP SS RH

Mine is 18p so someone must have changed it.

I’m wondering if I went back to the sea ray specs if the top speed and time to get on the plane would improve ?

When you say you can get 5000 rpm when you trim it up. Are you trimming it to the point where it cavitating? Are you having difficulty getting it to plane out? It sounds like you definitely don’t want to go up in pitch.

 

[Stray Current]

Do you know what the ratio of drive you have is, and if it is the same as what the boat was sold with?

I'm just thinking out loud here, but since the props are different than what the boat was sold with, you should probably verify that the drive ratio has not changed as well.

This. Definitely check that.

what is the listed maximum RPM on your air cleaner hat. I know mine is 4800 to 5500 and I was getting 4650 with a 2.2 to one drive and a 6.2 V8. I have the heavier 0508 version of the 260 then you do

I can tell you that I pitched my props from twenties to 19 and I picked up about 150 to 200 RPMs and lost one mile per hour. The boat was actually faster out at 4650 but I had more oil consumption because it was lugging.

If you’re only getting 4k trim in your either down on power or you’re not using the original gear ratio. Or you’re trimming it to the point where the prop is getting air to make 5K

 

[Lazy Daze]

Wait... don't go buying anything just yet. Something else is going on.

First, YES, you need to trim the drive up to get higher speeds. That is is normal/expected. And with that hull, you can use quite a bit of trim.

You're getting about 23MPH. You should be able (with stock props/gear ratio) to get high 30's to low 40's. Currently you are 2" shy of the stock props... that DOES NOT account for that drastic loss in speed.

The drive has some funky paint job going on. What does the hull look like? Your issue MAY just be excess drag created by a dirty hull or a lumpy paint job.

To explain the 18" prop set... the most "logical" explanation is that someone was running that boat with a larger load most of the time and wanted/was only concerned with hole shot and maintaining a lower/more comfortable cruisng/planing speed.

 

[Lazy Daze]

Oh... are you relaying your speed from the dash gauge or GPS? The pitot being partially clogged is another easy explanation for the low speed.