How fast can my boat go with bigger engine????

[SibAl]

I have an Avon 2.8m rib and currently have a 4hp Tohatsu outboard with an 18" shaft, but the transom i 16" so this is a bit long . It was the package I bought though and its a low hours outboard in very good condition and I got a great deal on it. The time has come to upgrade my outboard though and I've been looking for a few weeks for a replacement. The boat is rated to 8hp so am looking up to that. I havent seen any 8hp four stroke engines in my price range so I need to look at 6hp four stroke or 8hp two stroke. They both have the advantge of being a bit lighter than the 8hp four stroke.

What I would like to ask is does anyone know what speed I'm likely to get in one of thee with a 6hp and/or 8hp outboard. It probably wont help that I'm quite big at 17 stone. I usually have my son with me who is about 5 stone so the two person weight is probably about average, .

[Paul]

Andy B had a Yamaha 8hp four stroke high thrust outboard that was very impressive which pushed his Zodiac 380 (fish and hunt) hard floor sib to around 20 mph I seem to recall but being a later engine they can be expensive
If you're going to have the lad with you I'd personally look at a 10hp 2 stroke to get the job done ....... Andy's always messing about changing outboards and likely to have one to suit your needs/budget
Give him a PM

[Andy B]

Andy B had a Yamaha 8hp four stroke high thrust outboard that was very impressive, but being a later engine they can be expensive

I sold it for £950 if that's any indication of price/value.

I would imagine that fitted to a 2.8m Avon RIB would have been a good pairing. As for speed?
Got to be around mid 20's (mph) but i would be aware of the possibility of instability or chine walking?

My close friend does have a 9.9hp Suzuki 4 stroke fitted to a 2.7m Honwave and it does have a tendency to stand on it's arse

[Andy B]

Is this any good?
Nothing to do with me.....

https://www.gumtree.com/p/boats-kayaks- ... 1290780443

[The Hobbit]

Andy B had a Yamaha 8hp four stroke high thrust outboard that was very impressive, but being a later engine they can be expensive

I sold it for £950 if that's any indication of price/value.

I would imagine that fitted to a 2.8m Avon RIB would have been a good pairing. As for speed?
Got to be around mid 20's (mph) but i would be aware of the possibility of instability or chine walking?

My close friend does have a 9.9hp Suzuki 4 stroke fitted to a 2.7m Honwave and it does have a tendency to stand on it's arse

I know that feeling. I strapped my Yamaha 15D 2 stroke on the back of my 2.7 what a laugh, classic Jaws line...... I'm going to need a bigger boat........ enter the Honwave 3.8

[Andy B]

Yammy 8hp 4 stroke on Facebook.
https://www.facebook.com/groups/Ribsfor ... 7443463612

[Paul B]

I’ve got a lovely Suzuki df 9.9 converted to a 15 hp possibly for sale , which I can convert back to standard

[SibAl]

Thanks for the comments. My local chandlers has a Yamaha 2 stroke 8hp that is £600. They have offered me £450 part exchange on my 2012 Tohatsu 4hp 4 stroke. Sounds like that is the one to go for. I can try before I buy as well and get a 3 month warranty.

I may have a chance to get a 6hp four stroke at a good price and wondered if that would get me up on the plane, which is why I was asking the question. Not sure I'll be able to try before I buy on that one though. I'd prefer a 4 stroke but weight and cost of a 8ho 4 stroke may be the deciding factors.

[SibAl]

Ive got a chance to buy a 15hp 2 stroke from a local yacht club at a good price. Problem is the boat is only rated for 8hp. A 8hp 4 stroke and 15hp 2 stroke seem to be about the same weight so I'm going to go for it. Seems like a good excuse to upgrade the boat to one that can take a bigger engine as well.