What outboard should I buy?????

[Bulldog]

Hi
I need some help with powering a 5.4m cabin rib I don't know the make of the hull and am trying to get some pic up on Hear for some help with that .

The guy I got it from said he Had a 90 Suzuki and said it was way over powered but I have spoke to a few people some of them say 50hp some say 115hp what do I do the boat has new tubes and quite a shallow v hull so I'm thinking it won't need as much hp as a deep v ??????
I'm new to ribbing and need some help
Thanks

[NWDiver]

I have a 5.4m Avon Searider with a 90hp Yamaha on it. The 90hp works out great for this boat of the same hull size as yours. It'll do 44 mph empty on flat water and about 30-35mph fully loaded with four divers and their cold water gear. 90hp is the highest recommended hp outboard for this boat here in the US. It may be different in the UK.

[Poly]

Firstly, you need to be aware that rib.net represents a subset of the total population which is biased towards "top performance". On "fibnet" top speed is important so people like max HP for any given hull. Many boats will handle perfectly well with less power, and for "plodding" or cruising might be more than adequate. E.g. many sailing club rescue boats would be considered "underpowered" by rib.net standards but are perfect for the job they do, and even for more adventurous stuff.

There is an ISO standard for max HP on ribs. As I understand it if a manufacturer uses the formula it is assumed it is safe, if he wants to rate the hull for bigger then he has to demonstrate it is safe. See here: http://www.rib.net/forum/f36/engine-...tml#post145062

[chewy]

As Polwart said it all depends what you want to use it for?

[Ruari 29]

I have a 5.4 searider with a 4 stroke 50hp, I get onto plane but thats it, a bit sluggish. Your cabin will add extra weight, I reckon 70hp +.
As everyone else says depends what you want out the boat.

Sent from my Samsung Galaxy S using Rib.net

[Bulldog]

Thank you for your all the help

I am planing to do a bit of fishing in the Solent and hopefully a bit of ski/wake boarding plus my mum&dad live in the highland and we were hoping to do some island hopping is the inner sound so I want 4 people in the boat with a bit of camping gear we don't want to be breaking any speed records though

But I have a jet ski and that's 750cc 2stroke 90hp and pull ringos and flys with three people on it but won't pull a wakeboard up ( maybe my bad wake boarding tech) I thing that the rib will have more torque being prop powered but 2/3 in the boat and pulling a wakeboard is what I would like ( loads of you saying buy a bigger boat) lol

But the last thing I want to do is buy a big o/b and it not be safe.

[Pikey Dave]

A 115 Etec should sit nicely on the back of that

[Poly]

Originally Posted by Pikey Dave

A 115 Etec should sit nicely on the back of that

Thank goodness for that. I was starting to think Ribnetters were going soft!

Bulldog, perhaps you can get better pictures of the hull itself and any distinguishing features (if the tubes are original, even the type of valve or the way the seam is built might mean someone can identify it). It may of course be a one off / home built type affair, and certainly the cabin could be an afterthought.

Given its relatively shallow V I wonder if it might be something like a humber assault - which at 5.3 m they currently rate at 75HP and at 5.5m they allow up to 90 HP on.

[Ruari 29]

Come on bulldog, get some pictures on we want to see this beast.

Sent from my Samsung Galaxy S using Rib.net

[Alzi]

Originally Posted by Ruari 29

Come on bulldog, get some pictures on we want to see this beast.

Sent from my Samsung Galaxy S using Rib.net

Bulldogs Pics are located at the following Link

http://www.rib.net/forum/members/10087-albums.html


Alan.

[Pikey Dave]

Originally Posted by Polwart

Thank goodness for that. I was starting to think Ribnetters were going soft!

There's absolutely nothing worse than an underpowered boat. You don't have to use it, but it's nice to know it's there if you need it. I know which I'd rather have when it gets lumpy & you need to climb a hill or 2

[Bulldog]

Thanks for all your help lads I have put Some new pics of the transom and with the fixed tabs and the hull in my profile any one any ideas???I have looked online for best part of two years but the only hull close is a zoidac but its not got the splash well at the rear this must make the transom stronger

Chatting to a guy with a rib in Portland and he said 150hp but this is mad ????
There a few nice 150hp 2 stroke mercs about at the mo but like I say if I know what it is I could get the transom max weight and hp I think I should just get a 90hp and try it

[chewy]

I think some Deltas that were either 5m or 5.5m were rated to 150hp, an old review in a RIB mag said it was one of the best RIB's he used as you could place it where you want due to the power reserve.
I'm not saying a 150hp is the right engine for your RIB though.

[Poly]

Originally Posted by chewy

old review in a RIB mag said it was one of the best RIB's he used

oddly that sort of language crops up quite a lot in mags! I wouldn't mind if you also saw, just as frequently, "this is one of the worst boats I've ever used" or "whilst in expert hands the power was encouraging, it could be downright dangerous for a novice"

[chewy]

It was an article on black holes that it appeared in, the point is your better to have power in reserve and not use rather than sitting and thinking I was I bought that 90 rather than this 75....

[Pikey Dave]

Originally Posted by chewy

It was an article on black holes that it appeared in, the point is your better to have power in reserve and not use rather than sitting and thinking I was I bought that 90 rather than this 75....

At last, a man after my own heart All this nonsense about overpowered boats being dangerous, is just a rumour started by a bloke with a small engine

[jezza2011]

Hi I have a 75hp on my 5.35 and its very well suited to the hull.
good economy and good top end.
Just powerfull enought to get 2 crew and 6 divers moveing without issues.
and not too powerfull to over power the hull at top end empty.
I have personlay been hunting for a newer 90hp. but as mine is still going strong I am holding off for now.
There has been a few times I was glad of a little power in reserve to get me out of trouble.
Most people go for the maximum power you can afford and the boat will take safely.

[9D280]

Curveball time......

Is a lighter weight 75 going to give better handling than a lardy 90? If you don't have the mass to move, you don't need the extra power to move it.....

For example, the engine I took off clocked in at around the 110Kg mark. My current oil burner is 83Kg. I've not had it at full chat due to it being run in, but there is a perceptible improvement in handling even at 25:1 mix & restricted throttle...

Does your hull not have a plate somewhere that gives Max HP & engine weight? If not give the manufacturers a call. I got that info for mine within 2 mins of calling Humber.

[Bulldog]

Thanks 9d280

I don't know the make and there is no plate the tubes have been replaced by hensures and i called them they remember the boat well as it was I right pig to retube due to the cabin but hensures didn't know what hull it was the guy I got it from told me and hensures it was 5.4 sr but it's no way it's that ?????
I have pics in my profile if you want a look

[chewy]

Originally Posted by 9D280

Curveball time......

Is a lighter weight 75 going to give better handling than a lardy 90? If you don't have the mass to move, you don't need the extra power to move it.....

Yam 75 and Yam 90 are the same weight, be rude not to stick the 90 on

Originally Posted by Pikey Dave

At last, a man after my own heart All this nonsense about overpowered boats being dangerous, is just a rumour started by a bloke with a small engine

Yep, only go as fast as you you want it to go.