Engine Recommendation

[WotEver]

25 minutes ago, Pierre Thomas said:

After the 2nd alternator is taken in to account there’s less horsepower than I’ve got in theory at the moment. 

Only if the batteries are quite low. Otherwise it’s just a spinny thing that’s not doing much. 

[Pierre Thomas]

True. 

[peterboat]

3 hours ago, Pierre Thomas said:

That’s interesting Tony, I have yet to cause the slightest wash but increase in engine speed doesn’t give the increase I’d expect. What sort of horsepower would you expect for between 5-7 knots ? We’re quite bluff, though a bit more overhang than a tjalk at the bows, though the stern is quite similar. 

It is a very attractive offer and good price but I think I’ll do some more research and work this through with more brain than wallet so I’ll pass this time. After the 2nd alternator is taken in to account there’s less horsepower than I’ve got in theory at the moment. 

No probs it will sell  eBay or the forum

[Tony Brooks]

12 hours ago, Pierre Thomas said:

That’s interesting Tony, I have yet to cause the slightest wash but increase in engine speed doesn’t give the increase I’d expect. What sort of horsepower would you expect for between 5-7 knots ? We’re quite bluff, though a bit more overhang than a tjalk at the bows, though the stern is quite similar. 

It is a very attractive offer and good price but I think I’ll do some more research and work this through with more brain than wallet so I’ll pass this time. After the 2nd alternator is taken in to account there’s less horsepower than I’ve got in theory at the moment. 

I don't do HP calculations because its relates to hull shape and the propeller fitted. - its a black art as far as I am concerned. If you tell us the props pitch and diameter I am sure someone will be able to look up some prop curves and give you at least some idea. I think someone gave you a link to a prop calculator so if you put your boat's data into that play around with the HP or torque figure it should give you some idea. What I can say is that we had a number of wide beam hire cruisers on the Thames. They were about 42ft long and they has 2.2 litre engines coupled to hydraulic drives that are less efficient than a gearbox. They never seemed to lack power so we have to try all sorts of tricks to limit the throttle movement to stop hirers speeding. I have an idea they were about 52 bhp but much less at the engine speeds we ran them at.

 

If you are not making much wash  and the stern is not sqatting at speed I suspect that, without confirmation about the engine revs, the boat may be over propped. What is the engine's quoted maximum speed and what does it actually achieve at full throttle?