prop size

[emlclcy]

When I bought my boat the chaps selling it who is a marine engineer said it had a small prop. Going upstream the boat seems to struggle to make headway at 1500rmp. Then engine is a Perkins phoenix hooked to a prm30 box. I don't know the prop size or pitch. Any ideas how to sus out what it should have? The boats 57ft narrowboat

[Dalslandia]

What is gear ratio?

prop size is stamped on the propeller hub, maybe it is in the papers too?

what rpm do you get at WOT ? (wide open throttle)

[MtB]

When I bought my boat the chaps selling it who is a marine engineer said it had a small prop. Going upstream the boat seems to struggle to make headway at 1500rmp. Then engine is a Perkins phoenix hooked to a prm30 box. I don't know the prop size or pitch. Any ideas how to sus out what it should have? The boats 57ft narrowboat

 

 

Why have you picked 1500rpm to quote? Not 1000rpm, or 2000rpm, say?

 

Is it that 1500rpm is the max the engine will achieve in forward?

 

What speed is the 'red line' on this engine?

[emlclcy]

 

 

Why have you picked 1500rpm to quote? Not 1000rpm, or 2000rpm, say?

 

Is it that 1500rpm is the max the engine will achieve in forward?

 

What speed is the 'red line' on this engine?

1000rpm is for passing stationary boats 1500rpm is what feels comfortable as a max cruising rpm. This equates to a fastish walking pace. Don't know what the red line is but 15 sounds fast.

Your boat red lines at 200!!

[emlclcy]

What is gear ratio?

prop size is stamped on the propeller hub, maybe it is in the papers too?

what rpm do you get at WOT ? (wide open throttle)

I don't know the prop size will try and figure a way to look at it in the water.

Wot for me feels like 1500.

It's a 42hp 2ltr engine

Gear ratio is prm delta30 but not sure how this relates to engine rpm

[ditchcrawler]

1000rpm is for passing stationary boats 1500rpm is what feels comfortable as a max cruising rpm. This equates to a fastish walking pace. Don't know what the red line is but 15 sounds fast.

Your boat red lines at 200!!

So you are happy with the prop then. Lets face it if 1500 rpm gives you 3.7 mph, nice cruising speed, if the river is flowing at 2 mph you are only going to be making 1.7 mph over the ground.

[Dalslandia]

So you are happy with the prop then. Lets face it if 1500 rpm gives you 3.7 mph, nice cruising speed, if the river is flowing at 2 mph you are only going to be making 1.7 mph over the ground.

 

Or 5.7 :-)

[MtB]

I don't know the prop size will try and figure a way to look at it in the water.

Wot for me feels like 1500.

It's a 42hp 2ltr engine

Gear ratio is prm delta30 but not sure how this relates to engine rpm

 

 

Seriously overpowered for your boat then, I'd possit.

 

What diameter blade can you accommodate? This can be roughly determined from inside the boat by measuring the depth of the swim. Same as the height from the baseplate to the uxter plate, which can be measured from inside the engine room.

1000rpm is for passing stationary boats 1500rpm is what feels comfortable as a max cruising rpm. This equates to a fastish walking pace. Don't know what the red line is but 15 sounds fast.

Your boat red lines at 200!!

 

 

You have a rev counter though, from what you say. Is there no 'red line' max RPM marked on it?

[Dalslandia]

I don't know the prop size will try and figure a way to look at it in the water.

Wot for me feels like 1500.

It's a 42hp 2ltr engine

Gear ratio is prm delta30 but not sure how this relates to engine rpm

 

WOT is when the throttle is at the forward stop, the rev indicator or motor hand book give you the engine red line.

the gear ratio is the gearing of the engine speed to the propeller speed, and is very important, maybe it is 2:1 prop make half the engine rpm. Delta 30 have 1.53:1 2.09:1 or 2.83:1

 

your prop is probably 15-20" diameter and 10-15" in pitch, but to narrow it down more info is needed

 

www.prm-newage.com/media/File/delta%20man.pdf

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Edited December 29, 2015 by Dalslandia

[Bee]

Dalslandia is probably spot on but as a comparison the Beta 43 hp 1.9 litre(?) is a comparable engine and with a 2:1 reduction Beta recommends an 18 " dia prop by, I think 12" pitch, in my experience, with that engine and approx. that size prop (down an inch on dia and up an inch on pitch) with quite big blades that fill the 'Disc area' it feels right for the engine.

I would aim to fit 18 x 12 , just check Beta's recommendations on their website first and if you can fit it under the counter it won't be far out.

[Dalslandia]

Isn't the Perkins a "low" rev engine max 1800? ( can't find data on it)

[Boredrider]

Isn't the Perkins a "low" rev engine max 1800? ( can't find data on it)

 

Is this the same? http://www.canalworld.net/forums/index.php?showtopic=63285

[Dalslandia]

 

Is this the same? http://www.canalworld.net/forums/index.php?showtopic=63285

 

so same as the Beta 43 rpm 2800 (beta rec. 18x12)

 

it would need a 17x14.5 - 18.5x11 to get the RPM with a 2.09 GBx

Edited December 30, 2015 by Dalslandia

[emlclcy]

The engine plate has KF30276 stamped on it. Just trying to find my survey photos that show the prop

Gearbox is a prm delta30