slow birchwood 25

[robv1]

i have a ford 1800 diesel engine running a volvo 270 leg with the original prop (which i do not know what size or pitch it is )
i have been told that because the original engine was a 2 litre petrol it might now be overpropped it only runs at 5 knots what size prop do i need,also the bottom needs cleaning how many more knots would this achive its a birchwood 25
thanks rob

 

[Pete7]

I would give Lancing Marine a ring, not cheap but excellent advice available.

http://www.lancingmarine.com/

 

[Andrew_Fanner]

Diesel will run a tlower revs than petrol so in theory should need a different gearbox ratio to give the same prop speed. Alternatively up the pitch on the prop. Prop dimensions should be stamped on the hub.

 

[alb40]

What revs are you achieving? You should be getting 4800rpm at full power on a 1.8 ford. If you are getting lower, then you are overpropped. Lancing marine as said will be able to calculate the correct size for the boat.

With that engine, you will probably get in the region of 7 - 8 knots maximum. The birchwood is a planing hull and requires alot more power to make it go faster than that.