2002 300DA Prop Change?

[cpt-cortez]

2002 300DA with twin 6.2's and Bravo III's

Picked up the boat this year with only 360hrs on it, amazing condition for the age and only ever run in freshwater. After running the boat all summer I have some questions about prop sizing, planing RPM and WOT RPM - to me it seems that the boat is under propped for the 6.2L engines.

First off, I have to run 4000RPM minimum to hold on plane, even when light on fuel and water and that yields about 27-29MPH - seems like a pretty high planing RPM for a boat that is well powered? That is running zero trim tabs and neutral position on the legs. The boat comes up on plane very fast for a boat this size (i feel) but just seems to need a lot of RPM to stay on plane.

If I open the boat up to WOT it will run about 5300RPM if I keep the legs in negative trim, Trying to remember but I believe I was running about 38-40 MPH at this point. As soon as I raise the legs to neutral position, the RPM's will start to climb and give me an over-rev warning (not that i really like pushing the engines up into the 54-5500RPM range anyhow)

Based on the high WOT RPM and high RPM to stay on plane I feel the boat needs more pitch on the props. Does anyone know if the 300DA with 6.2L's runs a larger pitch than the standard configuration 300DA with 5.7's?

Any suggestions?

Thanks!

 

[scoflaw]

Well your not sayin what your running for props, or the B3's ratio. I'd bet your tach is off as well, rev limiter would never let you get to 5500.

 

[Woody]

Don't know if your boat would be the same but some literature I have for 2004 shows T-320hp 6.2's with B3 2.2 ratio, 24"pitch cup props, WOT rpm 5,200, WOT speed 48-52mph

It also shows the T-5.0 and T-350mag running 22" props

 

[cpt-cortez]

Thanks for your reply Woody. I need to verify what pitch is actually on my boat, will likely verify this fall when it gets pulled for service and storage. WOT speed of 48MPH is a lot more than what I remember seeing, I will open it up again this weekend and record the data, either way I should be able to run the legs in netural position at WOT and not over rev, makes no sense to run legs in negative trim at that high of RPM, not efficient and hard on the drive line I would imagine.

Would also be nice to stay on plane at closer to 3500RPM (or less!)..

Anyone have feedback on planing RPM on their 300DA? seems unusual to find this boat with the T-6.2's?? most are T-5.0's

 

[cpt-cortez]

Well your not sayin what your running for props, or the B3's ratio. I'd bet your tach is off as well, rev limiter would never let you get to 5500.

You may be correct, I do question how accurate the Tachs are. I'm Searcing for reference info on factory pitch and drive ratio.

 

[scoflaw]

I wasn't too happy with my 2006 280 da propping. I have very rough water here and it wouldn't stay on plane under 3k, it would always try to find its happy place around 3300. Was way too fast at that rpm, and pounded like hell. A think a 4-blade would have been the ticket.

 

[cpt-cortez]

Confirmed some details regarding my boat. Manufacturer states 2.20 drive ratio on the BIII drives and 14”x26” SS BR3 RH cupped & 15.25”x26” SS LH cupped props. WOT RPM 5200.

Going to run this in some prop selector programs I have found and also verify if this is what’s physically on the boat for props..

Something still seems off with my cruising speed, too speed and wide open RPM..

 

[StefanFL]

Try to trim your legs all the way up and you should be able to read numbers from props.
It might had T-5.0 and someone repowered to 6.2 without changing original 22p props.

According to your rpm and speed with 1:2.2 gear you are somewhat 22p with decent prop slip.

I'm not an expert, just did a lot of research recently to figure out issue with my boat, so had some spreadsheet handy to run your setup thru

 

[Brite Idea]

How did you end up? I just read this post and there's no way you should be running a 26" pitch. I'd say a 22" pitch would work on the boat but your RPM's do not match the what the numbers would be with a set of 26" props? I'd verify the tach first then go on to WOT numbers. Also I agree the rev limiter would prevent over revving.

 

[cpt-cortez]

well, boat is out for the winter and finally i can confirm the prop numbers;

Front Prop 48-823661 20P
Rear Prop 48-823662 20P

Seems like smaller pitch than what was expected.

Thinking back the boat was originally sold / used in Lake Tahoe so maybe it was propped down due to the high elevation? I'm only 1300' ASL where I run the boat on Okanagan lake so that might explain the over revving at WOT?

 

[Scott06]

Yes that would fit that boat is under propped if previously used at altitude. Best if you can find a prop shop that will let you play with a few pitches to dial it in.

 

[cpt-cortez]

Reviving this thread to see if anyone else might have some input as I came across an interesting comparison for propping.

2007 Cobalt 323 with T-6.2L and B3 legs, 2.20 drive ratio sitting at our marina and it has 48-823666/5 24P props on it... Boat weighs very similar 12,300lbs dry...

Can't for the life of me figure out why my boat would have the 48-823661/2 20P but its making more and more sense why this thing cant stay on plane below 4100RPM..

Anyone know a good source for prop sets? I'm honestly thinking of buying the props that are on the above mentioned Cobalt to try it out

any feedback would be appreciated!