Fuel storage question and speed question

[Rick Fisher]

I ordered a new Rib on the weekend. It was between the Highfield and the AB .. I went with the AB because it was in stock, the Highfield was 3 months away.

The only concern I have is fuel capacity. The boat is an AB 15 ALX .. and comes with only a 6 Gallon or 22 Liter Tank .. I knew this when ordering and figured I would have to get around it ..

The motor ended up being a 60HP Yamaha.. So I figure at WOT .. it has enough fuel capacity to run an hour.

I figure the boat will do 30 knots. Its got an aluminum hull and weighs 400 lbs.. or about 190 KG .. The motor is 260 lbs.. 60 hp.. The power to weight ratio is decent ..

Question .. I asked them to put another tank under the seat. I think it will be 6 gallons. Can someone safely store fuel in a portable tank ? Is there a bracket.. If its not safe, I don't want to do it .. Another 5 gallons would likely give this boat a range of 90 Knots depending on speed..

Second question .. What type of top speed would you expect a 15' Aluminum hulled AB RIB with a 60hp Yamaha to reach with 2 people on board ?

Thanks

[Rick Fisher]

Bump . anyone have any opinion on what speeds to expect from this boat? Will it cruise at 30 Kt ?

[Bigo]

Good power to weight ratio. All depends on max hull speeds and having the correct pitch prop on the engine. I would guess cruise speeds of 22-25 knots. I'm sure someone will come along and do some fancy maths for you!

[chipko]

Hi Rick,
Your new rig sounds good, have fun. I think you will easily achieve 30 knots and not be disappointed with fuel consumption.
As a very rough comparison we have a 5m rib with a 60hp Mariner motor which tops out at around 33 knots two up. It's not aluminium, so considerably heavier than yours (around 500kg) and is propped for towing wakeboards etc. so yours should better that if suitably propped. Cruising speed sweetest at around 22 knots with motor at 4000rpm.
Like yours we don't have an inbuilt tank but a 25l portable tank located under jockey/steering console. Never worked out mpg but a full tank will last us a good 3.5 hours run time consisting typically a mix of towing, cruising and bursts of WOT.
If messing around in the bay we just have the 25l tank and perhaps a 5l can as back up. For longer coastal jaunts we carry a second 25l tank which is just kept on deck not strapped down unless conditions dictate. Tend to move this around depending on load/conditions to improve trim.
Enjoy your new boat.

PS - Good thing about portable tanks is you can decant unused fuel in the car so your always using fresh fuel for the outboard.

[Rick Fisher]

Thanks for the feedback .. I did some reading on fuel storage.. The dealer put a 6 gallon in bow locker and 9 gallon under the bench seat .. so I should be fine..

I'm told I can put a steep pitch prop on this boat because the weight of the boat is low and will get out of the hole easy. I don't see it towing water sports.

In our area, the ocean gives you about 45 minutes notice .. speed can get you home without having to beat yourself to death.. This boat has an 18 degree deadrise so I would guess it will be fine with 2-3 foot waves, but get pretty bumpy above that ?

[two stroke mick]

The cruise speed will not be a function of power on that sized rib the cruise speed will be determined by sea conditions. A 5 m boat with 60 hp will do 30 to 34 on if loaded light in calm conditions. Off the west coast of Ireland I usually estimate a cruise speed of 17 to 20 kn. This has proven to be a realistic speed to cruise in a 5 m rib. Fuel burn at this speed is circa 13 lt of petrol per hr. Thus ,22 lt tank will give you about 1 hr 40 minutes run time. At work your fuel but will be circa 6 gal per hr.

For a 30 on avg cruise speed off the west coast of Ireland I think you would need a 7 m boat

Tsm

[Rick Fisher]

I watched a few videos of boating on the west coast of Ireland.. The waves I saw would be considered very rough weather here..
I am on the inside of Vancouver Island. The ocean is often like glass.. Really rough weather here is 1m waves.. 2m waves would be winter storm weather ..

I appreciate the reply. If the boat can cruise at 22 kts on a flat day, and hit 30 when feeling ambitious.. I will be happy ..

[Rick Fisher]

Got the new boat in the water, bit of a choppy day.. After the 2 hour break in period for the motor, I got it up to 27 mph .. This is according to the GPS .. The motor was at 4300 RPM ..

The boat rides as straight as an arrow. I'm very happy with the quality of the boat so far, fit and finish is great..

I can only assume at 5500 RPM or more, it would hit right around 33 knots as 2 stroke mick suggested... If it does exceed that speed, it probably shouldn't .. lol


Thanks