Horsepower for 8.3m rib

knewfie · 28 March 2017, 19:49

Hi There!

I was wondering if somebody would have some input on this. I am starting a boat tour and in the midst of acquiring an 8.3 metre rib from China. It will carry 12 people including crew. I'm thinking boat weight with people, engines and fuel will be about 5500lbs or 2500kg. As per the certification papers max horsepower is 224kW with engine weight of 432kg. I'd like to go with dual Yamaha 150 hp however I'd be 12kg over the max weight for the engines. So, I'm wondering if dual Yamaha 115 hp will cut the mustard. Whatta ya think?

Best,
Kier

breezeblock · 28 March 2017, 21:37

don't buy a rib from china is what I think and if its engines are heavier than the data plate suggests I can't see how it will get passed for commercial use

knewfie · 28 March 2017, 21:51

Thanks for the reply! Certainly no intention in exceeding the maximum certified engine weight. I was wondering if given this kind of boat, would 115s be enough? I can go with Mercury 150s for instance and they will come in under the max weight. Just would like to go with Yamaha due to their reliability and the fact there is a good dealer in the area.

I actually flew over to tour their factory and see the boat and how they build it. I was impressed to be honest. This particular model they are building for the military.

willk · 28 March 2017, 21:58

No comment on the Chinese RIB, but definitely go for twin 150! 115s will work (i.e. plane the boat) but with 12 PAX onboard would be extremely lacklustre. Twin 150s should take you to around the 40kts mark but will give you a much better hole shot (important if stopping and starting a lot - tours!)

Pikey Dave · 28 March 2017, 22:05

Quote:

Originally Posted by willk

No comment on the Chinese RIB, but definitely go for twin 150! 115s will work (i.e. plane the boat) but with 12 PAX onboard would be extremely lacklustre. Twin 150s should take you to around the 40kts mark but will give you a much better hole shot (important if stopping and starting a lot - tours!)

Notwithstanding the pedigree of the boat, even 300hp sounds a bit weedy for that size of craft/load. Maybe it's built on the light side[emoji848]

knewfie · 28 March 2017, 22:12

Thanks for the reply! Yes would love to go for the 150s however the Mercury dealer is over an hour drive away. I'm also a little concerned about the reliability compared to Yamaha. The other thing to mention is the water tends to be a bit rough around here so the times u can do 30 -40 kts are few and far between to be honest. We've also had several instances of people hitting whales lately when travelling 30 kts or so. So I'm wondering of the 115 might work out ok or would I have a hell of a time getting it up on plane..?

beamishken · 28 March 2017, 22:16

If you've been to the factory and built up a decent relationship with the makers couldn't you ask them to alter the weight limit on the build plate 12kg isn't going to make the slightest difference to the boat or ride but would allow you to fit the engines you want

willk · 28 March 2017, 22:19

Quote:

Originally Posted by knewfie

Thanks for the reply! Yes would love to go for the 150s however the Mercury dealer is over an hour drive away. I'm also a little concerned about the reliability compared to Yamaha. The other thing to mention is the water tends to be a bit rough around here so the times u can do 30 -40 kts are few and far between to be honest. We've also had several instances of people hitting whales lately when travelling 30 kts or so. So I'm wondering of the 115 might work out ok or would I have a hell of a time getting it up on plane..?

Well - Mercury 150s are self service - so that's a plus. An hour is very little in the greater scheme of repair shops. I'm three hours to mine. Tourism is all about the stops. Getting up and running is much easier with a bit of grunt and fuel efficiency is achieved at well below max revs.

Hittings whales country is where you want to run a whale watching business. Remember to watch them!

Poly · 28 March 2017, 22:54

Quote:

Originally Posted by knewfie

I'm also a little concerned about the reliability compared to Yamaha.

not much between them really

Quote:

The other thing to mention is the water tends to be a bit rough around here so the times u can do 30 -40 kts are few and far between to be honest.

all the more reason you need good acceleration.

Now I assume you have spoken to the CG (or whoever regulated boats in Canada). Their view on the construction and equipment will be most important.

Maximus · 28 March 2017, 23:06

My advice...Get some Camomile Lotion ready!..

You may well get Burned!...

Before you part with your hard earned ...I'd go with something you can see,try,appraise,AND TRIAL...whith a decent back up if it goes Tits up!

Mollers · 29 March 2017, 09:16

An 8.3m boat with twin 150s and 12 POB is going to be hopeless. I run a 7m with a 250hp single (greater power to weight than you are proposing). If I crammed that much humanity onboard it would kill it.

You'd need to be looking at 2x200 min. to shift that number of people around efficiently IMO.

Starovich · 29 March 2017, 10:40

Quote:

Originally Posted by Mollers

An 8.3m boat with twin 150s and 12 POB is going to be hopeless. I run a 7m with a 250hp single (greater power to weight than you are proposing). If I crammed that much humanity onboard it would kill it.

You'd need to be looking at 2x200 min. to shift that number of people around efficiently IMO.

Same here and I agree.

willk · 29 March 2017, 15:25

Quote:

Originally Posted by Mollers

An 8.3m boat with twin 150s and 12 POB is going to be hopeless. I run a 7m with a 250hp single (greater power to weight than you are proposing). If I crammed that much humanity onboard it would kill it.

You'd need to be looking at 2x200 min. to shift that number of people around efficiently IMO.

I'd beg to differ. Experience suggests twin 150hp works fine, but obviously depends on overall weights. Whale watching type trips don't involve fast passages or require wakeboard hole shots. That said - 115hp would be a joke

Hirta is 8 PAX but weighs well over two tons.

https://www.youtube.com/watch?v=VMosj1zinwE

Mollers · 29 March 2017, 18:03

Quote:

Originally Posted by willk

Whale watching type trips don't involve fast passages

Agreed, but I'd imagine that a lengthy passage could be involved. Wallowing about in a boat with dull throttle response and a heap of punters onboard would not be my idea of a day out.

12 peeps = 1000kg roughly, add boat, fuel, twins etc, etc.

matt h · 29 March 2017, 19:59

Twin 150 s would be hopeless on a loaded dinghy as said. By Mollers

) 2x200s or more.

GuyC · 29 March 2017, 20:23

224kW is 300hp so any more than that would be greater than the certification limit. It does seem a bit odd that the weight limit is less than the weight of two engines of the maximum power.

A 300hp single is around 300kgs so you could do that plus a smaller get you out of trouble engine.

Pikey Dave · 29 March 2017, 20:29

Quote:

Originally Posted by GuyC

224...It does seem a bit odd that the weight limit is less than the weight of two engines of the maximum power.

It's Chinese[emoji57] My 6.4 RC was rated to 300hp, with twin 115hp & 4 divers, it was no slouch, but extrapolate that to 8.3m & twin 150 + 12 pax= dog

Mollers · 29 March 2017, 21:29

Quote:

Originally Posted by Pikey Dave

It's Chinese[emoji57] My 6.4 RC was rated to 300hp, with twin 115hp & 4 divers, it was no slouch, but extrapolate that to 8.3m & twin 150 + 12 pax= dog

I think willk is trying to let our newb cousin down gently, rather than knock him down and give him kicking for good measure.

willk · 29 March 2017, 21:31

Quote:

Originally Posted by Mollers

I think willk is trying to let our newb cousin down gently...

Well spotted. You and matth agreeing on something was an unexpected bonus...

Pikey Dave · 29 March 2017, 21:36

Quote:

Originally Posted by Mollers

I think willk is trying to let our newb cousin down gently, rather than knock him down and give him kicking for good measure.

If he wants it dressing up in pink ribbons, he's in the wrong place. It might be harsh, but I've his best interests at heart.
"You can sprinkle glitter on a turd, but all you end up with is a sparkly turd"