advice on engine size please

dirtrider212002 · 31 August 2008, 22:35

hi there i purchased my first boat a couple of weeks ago a b-square marine pro shore 2.9m. It came with a yamaha 5hp. it will just get on a plane with myself only but i would like it to plain with atleast 2 people preferably 3. the boat has a max engine size of 10hp but i have found a 1983 2 stroke yamaha 15hp engine. Basically i want to no if it is going to be far to big/powerful and heavy or if it will be to dangerouse. Any advice is greatly apreciated thanks.

Locozodiac · 01 September 2008, 00:53

Quote:

Originally Posted by dirtrider212002

hi there i purchased my first boat a couple of weeks ago a b-square marine pro shore 2.9m. It came with a yamaha 5hp. it will just get on a plane with myself only but i would like it to plain with atleast 2 people preferably 3. the boat has a max engine size of 10hp but i have found a 1983 2 stroke yamaha 15hp engine. Basically i want to no if it is going to be far to big/powerful and heavy or if it will be to dangerouse. Any advice is greatly apreciated thanks.

2.9 Standard sibs with ply or alu decks are rated for Max 10 HP engines, newer engines weight the same in the 10/15 range, don't know for a Yam 15 so old compared to modern ones. If the 15 does not exceed the max transom weight, use with caution, inflate your sib well to it's rated woking pressure. It should plane properly with 3 up, distribute passengers weight to sib mid/front deck. Practice full throttle hole shot to see boat's behaviour until you are a skilled sibber. Is it illegal to overpower a sib in UK ?

Happy Sibbing

9D280 · 01 September 2008, 10:05

Quote:

Originally Posted by Locozodiac

. Is it illegal to overpower a sib in UK ?

Don't think it's illegal in the "go directly to jail" sense, but the insurance bods will just laugh at you when you claim for the broken transom....... and should someone get injured by what will be an technically uninsured boat .....

My reccommendation would be to stay within the "max" numbers on the transom plate.

Locozodiac · 01 September 2008, 17:21

Quote:

Originally Posted by 9D280

Don't think it's illegal in the "go directly to jail" sense, but the insurance bods will just laugh at you when you claim for the broken transom....... and should someone get injured by what will be an technically uninsured boat .....

My reccommendation would be to stay within the "max" numbers on the transom plate.

Just to know better UK boating. Must all sibs/ribs be insured locally as a general rule (it's the law), or will depend entirely up to you being insured or not ? dirtrider212002 has not specified if it's a air or aluminum 2.90 deck floor, and the floor type will make a difference in rigidity and performance.

As a comment for countries that don't need local inssurance issues :The only difference between a 2.90 and a 320 which accepts a 15 HP engine is only 30 cm in lenght, both have the same tube, about 40 and same width about 1.50 Mt with same transom. So 5 Hp more is not that big over powering difference, should make a 2.90 plane faster and carry heavier weight. If you are a experienced boater I'm sure will use it properly with caution. As a safety issue, overpowering is not recommended to newbies.

Happy Sibbing

dirtrider212002 · 01 September 2008, 20:25

hi there thanks everyone for comenting. the boat i have got is a wooden floor and when it is pumped up to corrct pressure is realy suprisingly rigid. i am new to boating but would be very very cautious so i dont think that is an issue. if i was to go for this 15hp would i be able to use it on my own or would it be to powerful or just throttle on gently.

Poly · 01 September 2008, 20:33

Quote:

Originally Posted by Locozodiac

Just to know better UK boating. Must all sibs/ribs be insured locally as a general rule (it's the law), or will depend entirely up to you being insured or not ? dirtrider212002 has not specified if it's a air or aluminum 2.90 deck floor, and the floor type will make a difference in rigidity and performance.

no legal requirement for insurance to use a boat on open water in the UK. Some harbour authorities and publicly owned slipways etc wll require insurance to let you put the boat in the water.

Locozodiac · 01 September 2008, 22:17

Quote:

Originally Posted by dirtrider212002

hi there thanks everyone for comenting. the boat i have got is a wooden floor and when it is pumped up to corrct pressure is realy suprisingly rigid. i am new to boating but would be very very cautious so i dont think that is an issue. if i was to go for this 15hp would i be able to use it on my own or would it be to powerful or just throttle on gently.

See first if the 15 HP weight is compatible/safe for the 2.90 transom, this information must be in the sib's owner manual tech specs. Or ask the dealer about it. Is not the same, 3 boys up than 3 adult up, probably a 2.90 with 15 HP driven by 3 boys will fly compared to same 3 adults. Is a matter of accelerating to see/experiment sib's behaviour at different speeds. Would be advisable to adjust a bit the engine steering friction bolt to have a light heavy steering if going for a 15 HP engine. If too light you can lose tiller/sib control. A 15 HP is theorically 3 times faster on calm waters than your actual 05.

Back in 96 used to own a OMC (Zodiac 3.05) with a Evi 10 HP, the top HP the boat could handle, modified the engine to 15 HP and performed much nicer, that is, better hole shot with more weight and slight better end speed. On the other hand if you buy a 15 HP will be perfect for a larger sib update up to a 3.30 mtr.sib. Go for it, but use with caution untill you are confident to have mastered the small beast.

Some Ribnetters will prob say "how can I recommend a newbie to go for a larger engine" so, if possible go with the 15 HP current owner on a engine/sib sea test on calm waters to see/feel it's performance at different speeds before buying. I'm sure in a short trial will be used to the new engine/sib configuration. The final decision is entirely yours.

Happy Sibbing

Poly · 01 September 2008, 22:28

Are B-square the boats sold at Lidl (or is it Aldi?) ? Don't now what the build quality is like - some of their other stuff seems to be OK, function over form, but I doubt it was designed for serious power/speed - but rather as a cheap run about / tender.

prairie tuber · 03 September 2008, 06:01

I think a 10 hp might be just enough to get 2 people on plane, but will have a pretty hard time getting 3 people on plane.

fred bolton · 03 September 2008, 07:44

Quote:

Originally Posted by Polwart

no legal requirement for insurance to use a boat on open water in the UK. Some harbour authorities and publicly owned slipways etc wll require insurance to let you put the boat in the water.

Gwynedd council require boats with engines above 10hp to register with them at £15( you must have insurance to register), then charge you £15 per launch.

MrT · 03 September 2008, 22:23

Hi dirtrider212002,

In 2001 i bought a wetline SIB, but couldnt decide whether to get the 290 or the 310. the 290 was rated at 10hp, the 310 at 15hp, and at the time i didnt have an engine. Money was tight and there was £100 difference in the cost, so the chandlers let me take both home to decide.

Once inflated, there was actually only about 3 inches difference in the length, so I went for the cheaper option, and bought an old Mariner 15 which i beleive is a re-badged yamaha. It is exactly the same size and weight as the 9.9 which my friend has. I have just upgraded to a Honwave 3.8 with air v floor, and am still using the same engine so I'm glad i got the 15hp.

I will say however that I bought the 290 with an inflatable floor under which was the inflatable keel, and the first time i opened up the engine, the transom kicked in at the bottom, and the floor started to buckle up so i bought a ply floor for it, and put the inflatable floor on top of it. Never had any problems after that!

I have since realised that in all the years I had the 290, I dont think that I ever had it inflated to the correct pressure, as the high speed inflator I was sold at the time for about £70 only went up to about 0.18 Bar when it should have had 0.25 Bar. With the correct pressure it may have been OK with the inflatable floor, who knows?

If I was you I would go for the Yamaha 15, but be careful-remember you dont have to open it up all the way!

I hope that sharing my experience helps, All the best.

GraemeCooper · 04 September 2008, 09:32

I agree with Mr T. I have been researching SIBs for some time now looking at using one for diving - so weight to engine power and planing are key issues. The Quicksilver 380 is rated to 25 HP - but many I have looked at have had 30HP 32 Strokes - the main issues seems to be the weight - and many seem to have been downrated due to the weight of modern 4 strokes. Having sadi than many dealers will not sell you a package with an engine above the recommended - but they will sell you the boat and engine separately. Also, you dont need to full open the engine up if only one or two on board, but it gives the power if needed. As with all things though you have to accept responsibility if you go outside of the manufacturers recemmendations.

Locozodiac · 04 September 2008, 17:12

Quote:

Originally Posted by GraemeCooper

I agree with Mr T. Also, you dont need to full open the engine up if only one or two on board, but it gives the power if needed. As with all things though you have to accept responsibility if you go outside of the manufacturers recemmendations.

Outside yourself responsabilities, you only need to full throttle to move bigger loads, more buddies and plane faster, once on plane, reduce throttle to 3/4 cruise speed, ideal to get under way fast and have fuel economy.

Happy Sibbing