What Prop should I use??

[webegonebeachin]

I have a '87 Bayliner,2550 with a 9'beam,5.7 Merc.outdrive.I want to improve performance and would like to install a SS prop.What pitch (SIZE) would be recommended?? WOT only gets me 25mph! Any Info would be appreciated.

 

[chuckz]

Re: What Prop should I use??

In order to answer your question, you need to post the size of the prop on the boat now and WOT RPM.

 

[webegonebeachin]

Re: What Prop should I use??

Thanx, 14.5 x 15,WOT was approx 3600!!

 

[walleyehed]

Re: What Prop should I use??

You're about 1000RPM shy of where it should be...maybe even 1500. we turn our 5.7 5500RPM all day long and have since about 1990.<br />Has it always been this way????

 

[LubeDude]

Re: What Prop should I use??

Are you sure your tach is accurate? <br /><br />Thats a small Pitch prop, I think something is amiss.

 

[walleyehed]

Re: What Prop should I use??

I think the readings are correct, LD...the speedo may be off by 1, maybe 2MPH, but 3600 with a 15 on that unit comes close to 23-24MPH.<br />That's figuring a very low slip ratio, so I think the tach is good.<br />I DO think something else is troubling us here though...our 22 wellcraft cuddy with a 5.7 will spin a 19 6k...we run a 21 to keep it managable.

 

[LubeDude]

Re: What Prop should I use??

Originally posted by walleyehed:<br /> I DO think something else is troubling us here though...our 22 wellcraft cuddy with a 5.7 will spin a 19 6k...we run a 21 to keep it managable.

This is what is troubling me here, it seems that the 15P should be spinning a higher RPM.

 

[walleyehed]

Re: What Prop should I use??

Exactly.....we may have engine issues, possible marine growth, bad trim cylinders not going all the way down, hull full of water, etc..<br />My question to him is "Has it always been this way?", and do we know for sure it's a 15 pitch?

 

[webegonebeachin]

Re: What Prop should I use??

Thanks All: I ran the boat 1st time last summer,just purchased.Trim tabs seem to go all the way down,I am 99% that prop is stated size(its in storage)Bottom is painted,no growth.Engine seemed to start/run fine.Any ideas on where to start looking/fixing????

 

[webegonebeachin]

Re: What Prop should I use??

Originally posted by walleyehed:<br /> You're about 1000RPM shy of where it should be...maybe even 1500. we turn our 5.7 5500RPM all day long and have since about 1990.<br />Has it always been this way????

 

[walleyehed]

Re: What Prop should I use??

May need to have a tech do a tune-up, webegone...<br />Your RPM seems to be correct in regards to speed with a 15" pitch.<br />Tabs are down you say, but is the drive going clear down???<br />When on plane, can you raise the tabs without problems??? Does the bow stay down??<br />If tabs are up, what happens if you start to trim up?? RPM go up?? any advance in speed at that point??<br />I know, too many questions, but lets make sure we're not fighting the trim systems (tabs and trim).