engine size

Hi, could anyone tell me if a 3 1/2hp outboard will be big enough for around the blackwater estuary off Steeple. I know that a 4hp is recommended but as I have been offered an almost new one I am hoping it will do the job. Having done a lot of water skiing in the area many years ago I do know that the outgoing tide realy does pull and if I was ever coming back up river, under power, against both tide and wind would I make any headway or just stand still. Any comments or experiences would be vary helpfull. Regards Peter.

Hi Peter,

Apologies for a lack of any earlier response!

Given the physics of displacement hulls, ( http://en.wikipedia.org/wiki/Hull_speed ) speed of current in flat water should not be the issue to be concerned about, because a SeaHawk will never manage to beat anything much more than a 6 knot current.

The reason you may need something beefier than 1.5hp (the original inboard engine power that was fitted to SeaHawks) is waves. Bare in mind that hull speed calculations assume horizontal water. The lowest power engine, given an appropriate prop, even my little electric motor with just 50lbs of thrust, is capable of pushing a SeaHawk through level water at its hull speed.

The reason why you may need something with more grunt is pushing the full weight of boat, crew and provisions, up waves. That's where a less powerful engine will begin to struggle.

There are a good number of people who use 2.5hp engines and swear by them - but they are frequently Broads-based where there are no waves to speak of.

It all depends on whether you feel you need to be prepared to encounter significant wind against tide effects or other wave-inducing conditions as to whether you need the comfort of knowing you have the grunt available to fight waves. Current is another matter. You may never beat that in full flood.

Hi Gregg, thank you for your information,it makes me think my best option is to is test out the engine against the outgoing tide just off Steeple where i will be doing my sailing. The engine is a 3.5hp not a 1.5hp and reading your reply I do feel a little more confident that it will be OK.The person I am buying the engine off is a good friend of mine and is happy to let me try it out first.Like I mentioned in some of my other messages I did use to ski in this area and seem to remember that the incoming tide never seemed as bad as the outgoing rush. Just to let you know that your webb site has helped me no end in my work on my seahawk and that things are getting to a stage where I can see the end. The trailer is now finished and much lighter so I can handle it on my own. I have decided not to paint her till next winter so I can get her in the water and start to learn how to sail correctly. Hopefully all will be ready by the end of May.I will try to get some photo's and then work out how to get them to you via email.I keep watching foleybrown's vidios on youtube and anything else I can find and believe me I just can't wait to get on the water. Once again many thanks for all your help Peter.  

Hi Peter,

I don't fully understand the physics of the thing, but I have been told that because of the slow revving nature of the inboard engine and its heavy flywheel, the old Inboard 1.5hp engine has similar grunt for climbing waves as a light-weight high-revving outboard at 3.5hp.

I've also mentioned to people that ask about engines, in the past, that despite the recommendation for a 4hp engine in the brochure, Reedcraft supplied a 3.5hp Yamaha two-stoke to my father when he bought his SeaHawk from them, so I doubt that you'll find any significant problem with your friend's, in terms of performance against tide, but obviously, there's nothing better than a test in real world conditions.

Best of luck and good wishes for the coming season.