[desy]

i would like to but an engine for my new boat but having probz i dont know what the hulls like and i want to got a descent speed for a 20ft boat im looking for i price no more than 200quid






help will greatly be apreciated thx

 

[Shropfisher]

For £200 it sounds like you need a paddle, The engine is your life, if it fails your in trouble, never been better money spent, than on a decent motor. up your budget and think safety.

 

[predator1]

try www.ebay.co.uk normally you can pick up a bargain on there but make sure you see the engine running, and that a good spray of water is coming out if it is water cooled which most are and always look for a serial number on it, as some maybe stolen and you dont want to pay good money for an outboard and later find out its stolen .
tight lines

 

[Peter B]

Hi desy,

I agree with shropfisher, it will be false economy to buy anything but a previously well-maintained, sound and reliable engine for your boat which you have seen running for an extended period at throttle settings from tick over to full chat, and preferably at sea.

Presume you're looking for an outboard rather than inboard engine. If so don't forget that your hull shape is very important and more or less determines what horse power you're looking for in your engine.

If your boat has a displacement hull it will have a maximum speed above which it will not go no matter how many horse power you put on its transome. So the trick with a displacement hull is to buy just the right amount of HP to obtain the boat's maximum speed. Any more HP just wastes fuel.

If it has a planing hull then the speed you get will be proportional to the horse power up to the point where the speed becomes dangerously high for the boat's stability. So here again with a planing hull you should look for enough HP to get the boat comfortably up on the plane, and stick at that.

In any event, I agree again with shropfisher; I'm afraid your budget is a bit meagre for what you're looking for.

Cheers, and good luck anyway with you new boat.........

 

[Peter B]

Sorry desy, I forgot to tell you. The theoretical maximum speed for a displacement hull is roughtly 1.34 x square root water line length. So if your boat has a displacement hull and has, say, an 18 foot waterline length, its theoretical maximum speed is about 5.7 knots.

OK?

Cheers

 

[sciroccoGTX]

Sorry desy, I forgot to tell you. The theoretical maximum speed for a displacement hull is roughtly 1.34 x square root water line length.

Mmmmm, very interesting. I knew that the speed of a displacement hull was limited i.e. a bigger engine doesn't mean a faster boat, now I've learnt the 'theoretical' formula.

Thanks Peter

 

[magicdog]

Greetings all - my first post

Hope it's OK to hijack this thread:

I'm new to this mularkey too and bit the bullet last October with a second-hand 17' Tidemaster and 5HP Mariner.
I really want to up the horses a little and the advice I've been given is a 10HP max - much more being of little use. Does this sound about right?

She's an open boat with a displacement hull in clinker stylee GRP and a seven foot beam.

I was also wondering if a fifteen horse engine would be too much?

Any help gratefully received...

 

[Peter B]

Hi magicdog, welcome to WSF - a friendly, helpful and happy place!

Are you sure your hull is a full displacement hull? I thought Tidemaster boats were semi-displacement, and certainly the two Tidemasters in my harbour are semi-displacement. This is a tricky subject, mate, and I am no expert, but here's a pic of the most common hull shapes.......... If your hull shape is anything BUT the top one, then you will get more speed from more horse power, and I should think a 15 would not be wasted. If you have a true displacement hull though, like the top one shown here, and where the hull at the stern does not rise, but stays at the same depth as the rest of the keel, then I think you should stick at 10HP because your theoretical maximum speed will be about 5 kts.

You may be able to make a judgement from the speed you get from your 5HP engine. Do you know what this is? If not try to find someone with a hand held GPS and borrow it to find your speed flat out with 5HP, and judge from that what increase you might get from more HP.

Hope this helps, and good luck with it.............

Cheers

 

[magicdog]

Thanks for the prompt reply.

I could send you a pic of it if that would help - it looks similar to an Orkney Longliner...

 

[Peter B]

Ahhhh, you've lost me there a bit mate. No pics thanks.

Is your boat a Tidemaster or an Orkney Longliner? There's a bit of a difference!!!

My last post gave you the basic hull shapes, and that's what matters, so have a look at your hull, whatever make it is, decide whether it's a full displacement or a semi-displacement and take it from there.

Best wishes ..................

 

[wilson17]

Ahhhh, you've lost me there a bit mate. No pics thanks.

Is your boat a Tidemaster or an Orkney Longliner? There's a bit of a difference!!!

My last post gave you the basic hull shapes, and that's what matters, so have a look at your hull, whatever make it is, decide whether it's a full displacement or a semi-displacement and take it from there.

Best wishes ..................

jvkcdjijksosi

 

[magicdog]

jvkcdjijksosi

Que?

 

[Nos4r2]

IMHO I'd stick a 15hp on there anyway as at displacement speeds it'll be very understressed-you don't HAVE to use full throttle...and if the weather turns a bit nasty a 5hp will have problems pushing you at even displacement speeds.

BTW Desv if you want an engine for under £200 to push a 20ft boat I'd suggest having a look on the local for sale boards round any local canals. Most canal/river use outboards don't have many hours on them and have only ever been in fresh water-or look for an ex MOD engine. I've had 2 of them. They ain't pretty and the MOD spec them w/out serial numbers so insurance is a pain but they tend to be barely used. I'm running a 1987 ex MOD Mariner 50 at the moment and it's barely got any wear on it.

 

[magicdog]

Good point but the 15HP Four-Strokes are getting a little heavy to handle without help and I'm not sure about towing with a 15HP bolted on the transom.

I'm gonna try a Honda 10HP F/S and go from there...