5.8 Volvo Penta DP-C1 Prop upgrade?

[Burns363R]

Okay heres the skinny.

1) Wanting more Top Speed
2) Volvo stock Duo prop Aluminum
3) 21p i believe
4) WOT was showing 4900 RPM and GPS was 45 mph
5) 1995 Volvo Penta 5.8l 235 hp i believe
6) Celebrity 210

I was thinking i probably could get away with a more agressive prop. Volvo recomends 4400 on there drives for max speed apparently. So i could get more speed at a lower rpm. I just dont know where to go from there.

 

[bruceb58]

The Volvo props are not spec'd with a pitch. They use a number. Which number prop are you using?

http://www.volvopenta.com/SiteCollectionDocuments/Penta/Propeller guide/Propeller Guide.pdf

 

[Burns363R]

B7 i think it was.

 

[Burns363R]

Looks like i could get a B8

 

[bruceb58]

I would see if a marine dealer would let you try them first. B8 is the largest pitch prop you can get. You could also switch to a stainless type C prop.

Type B props have been replaced by a type J prop. J props have 4 blades for the rear prop. They are quite a bit more money that B props though.

Make sure you do your test with a full fuel tank and put enough people on the boat to simulate a full load.

Make sure your tach is accurate. Put a shop tach on there to make sure your RPM's are really what you think they are.

Look at your props for the serial numbers to determine what you actually have.

 

[jhnmdahl]

Sounds like a B8 would work for you, but given the cost of these I second the idea of finding a shop that will let you test a few different options before buying. Props for Volvos are pricey, especially when you're buying them two at a time.

 

[steelespike]

Based on the pitch given and using 1.51 ratio calculator says 30% slip.
So some info is wrong. Being a duo prop perhaps 1.51 is wrong.

 

[bruceb58]

Based on the pitch given and using 1.51 ratio.

He does not have a 1.51 ratio and forget the pitch. The pitch is not supplied with the specs of these props.

 

[bruceb58]

For a prop chart with speeds, go to this post:
http://forums.iboats.com/forum/gene...questions-and-topics/539405-what-size-duoprop

 

[Burns363R]

I was wrong its a B5 prop. That will make more sense. So i should probably do a B6

 

[Burns363R]

So that is the question do i do a B6 or a C6. I have found a C6 setup for less than $500 used. The boat trims out at 48mph GPS with the B5 in good water turning 4900-5000 RPM according to my tach. Does the math add up on that? I deffinatly will verify the tach before buying anything, but assuming all is right will going to a 6 be enough?

 

[Scott Danforth]

if you found a C6 setup for $500 used, jump on it. I boat in an area of constantly shifting channels, submerged boats, etc, so my prop guys know me by my first name. because of that I wouldnt consider stainless.

 

[bruceb58]

Is that C6 set the one on eBay?

 

[Maclin]

.... The boat trims out at 48mph GPS with the B5 in good water turning 4900-5000 RPM according to my tach. Does the math add up on that? ...

Yes, it does. With my B5's I can see 48mph on a good day at 4600rpm, 46mph any other day.

 

[Burns363R]

So then i should be good on a C6 prop. How much will that lower my RPM? Volvo only wanted 4400 RPM max. Does that mean someone switched my prop?

 

[Burns363R]

ya the C6 on ebay

 

[bruceb58]

So then i should be good on a C6 prop. How much will that lower my RPM? Volvo only wanted 4400 RPM max. Does that mean someone switched my prop?

Not necessarily.

Check your tach to make sure you are at the right RPM.

Sometimes its better to have a lower pitch prop if you are running at altitude or with heavy loads on board. Not sure under what conditions you are going to be running at. If you think you may run at higher altitudes at some point, keep the B5s for then.

When you are running your boat currently, are you running it with the number of people on board that you normally have? How about all your gear and fuel?

 

[Burns363R]

That was 2 people and 3/4 tank fuel and all gear. Boat holds 9 people. But I would assume since max RPM is 4400, i would want to shoot for that at no load in the boat. Then when i load the boat, obviously my top speed and max RPM will drop due to lack of HP. But thats whats supposed to happen. I shoudnt be able to out run my prop with no load is how i understand it.

Also altitude wont be changing much, and i will verify my tach before i purchase anything.

 

[Scott Danforth]

you want to shoot for max RPM with the boat loaded like you use it. you can control the RPM's with the throttle when you are lightly loaded. your VP should also have came with a rev limiter (little black box bolted to the transom and connected to the coil)

 

[Burns363R]

No rev limiter.