Volvo DP290 prop sizing

[zapcat]

So finally I have stripped off the many layers of paint and have found the all important numbers on my props - B5 !

Following successful sea trials in the Summer after a complete refit, once the engines were run in, I have found that I am achieving max rpm (4,600rpm) at about 3/4 throttle. I think this is just before the second choke opens. Fantastic initial acceleration and also achieving excellent midrange acceleration. At 4,500 rpm I had 45mph on the speedo and 38knots on the GPS. No problems with the engines at all across the rev range.

Full details are:

2 x brand new 5.7ltr GM V8 315hp per engine - 630hp total
2 x re-furbished DP 290 drives running B5 props
Vessel - Triana Tropica 25ft
Approx weight 4 tons - this is a calculated approximation
Max rpm at WOT 4300 - 4600

There is video on my Youtube account at https://www.youtube.com/watch?v=m2vgqajBAsA&index=4&list=FLAtcG8x6H83Naaig8cCLw6Q

Can anyone advise on what props I should be changing to? And is anyone looking for some undamaged B5 props when I carry out the change?

Any help greatly appreciated

 

[dpb]

You are looking to go up in number, ie B6, B7 or B8.
But unless you find someone with very similar boat and engine set up it will be trial and error I think.
If the props were original, what was the original engine power, you might be able to use that info to help your answer using the VP prop guide.
My guess would be B7 but it is an expensive trial and error!!

 

[zapcat]

Thanks for your reply - any idea if anyone does an exchange scheme sort of thing? I know i am at a disadvantage as I need two pairs

 

[Scarron]

Hi Steve

Sounds [and looks] like JayKay is going pretty well, you must be really chuffed. Even though we are single engined with a DP290 [1:78 ratio] I think we provide a reasonable comparison, variously we achieve;-

B4, 42kts at 5400rpm
C4, 43knots at 5250rpm
B5, 43 knots at 5000rpm
B6, 45knots at 4650rpm
C7, 42kts at 4200rpm

As you can see I have spent quite some time prop testing, it appears that you will gain/loose about 400 rpm for each change in prop number and about 4 knots providing the engines horsepower and torque is sufficient to pull the revs . I am sure you will be able pull B6s which should pick up another 4 knots to 42 and theoretically B7s should give you another 4knots to take you to 46, worth a go I should have thought?

I have one pair of B6s you are welcome to borrow for trials [or any of the others in my collection...]

I have just put on a pair of C5s which I hope will be the right compromise, need to go out for some speed testing..

Paul

 

[zapcat]

Hi Paul

Thanks for the offer, I will take you up on the loan of the B6s and will try to source another pair - we will not be back in the water until April so it will be a while before I need them so will get in touch closer to the time.

Jaykay fully met expectations/hopes but a temporary fuel system did give problems at full tank or low tank so looking forward to new season with a half decent tank.

I tried to find pics of the CPR but couldn't find any by searching internet, hoping to get there next year fingers crossed.

Cheers

 

[zapcat]

Hi Paul

Thanks for the offer, I will take you up on the loan of the B6s and will try to source another pair - we will not be back in the water until April so it will be a while before I need them so will get in touch closer to the time.

Jaykay fully met expectations/hopes but a temporary fuel system did give problems at full tank or low tank so looking forward to new season with a half decent tank.

I tried to find pics of the CPR but couldn't find any by searching internet, hoping to get there next year fingers crossed.

Cheers

 

[[2068]]

The bit I am confused is that max rpm for a small block V8 is generally 4800-5200 rpm.
If 4600rpm was at 3/4 throttle, how do you know what WOT was?
Factoring in that you were probably lightly loaded at the time, the engines are in perfect condition, sea state flat?, the hull is unfouled ... I'd be wary of going "up" any sizes beyond the B5 without more trials.

If it is the case the 4600rpm is indeed WOT, I would consider dropping one size to a B4.

.