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-   -   twin outboards on sib? (http://www.rib.net/forum/f50/twin-outboards-on-sib-43614.html)

White2505 25 August 2011 09:34

twin outboards on sib?
 
Hi all,
looking for some advice.

Pretty sure I'm going with a 3-4m SIB (depends on what comes up at the right price!)

I'll be primarily using it for fishing and messing around on a tidal estuary and inshore off the North Devon coast (tidal range is typically between 3 and 10m)

obviously safety is one of my primary concerns, don't want to be disappearing off into the Bristol channel!

A sib in the range I'm looking at typically looks like it is rated for around a 10hp outboard.
Is there any reason not to go with a couple of small 3-5hp outboards to give myself that safety margin if one engine won't start?
or will a typical sib struggle with the transom weight of two 5's compared to a single 10?

hope that all makes sense.

Poly 25 August 2011 09:40

With big currents / tides 3HP is probably going to struggle to get you home at a sensible speed. Possibly fine for an aux which is a fall back position and where you might limp to somewhere, or keep yourself in one place waiting for a tow. Bear in mind that 2x3HP is twice as likely to develop a fault with one of the engines as 1x6HP and so see you using a single engine twice as often as you would need to revert to an aux with a bigger single. Its also a lot of extra weight and hassle which I don't think you really need. Probably better to spend the servicing cost of 2 engines on looking after 1 really well so it always goes!

willk 25 August 2011 10:17

Twins on a SIB is going to wreck yer head - in so many ways.

My advice is buy a decent engine (not new perhaps, but a good example with some history) and keep it well serviced. Learn how to sort the basic problems that occur at sea and carry a decent spares/repairs kit. After that make sure you have a very good anchoring system and a VHF. Help is never far away.
Bear in mind that IF the wind and/or tide is going the way you want, a pair of oars will be very useful and never fail to start ;)

Common engine problems are:
Water in fuel (easily guarded against)
No fuel - ditto
Damaged fuel line - carry spare
Broken starter rope - carry spare and tools
Oiled spark plugs - carry spares and tools

There is some useful chit chat about SIB equipment and spares here: Linky

Mollers 25 August 2011 10:31

I'd go for a pair of VHF or even a personal EPIRB rather than extra outboards. Don't think that all outboards are tempermental nightmares. A well serviced modern O/Bs are pretty reliable. :)

White2505 25 August 2011 10:46

Thanks for that.
I've done a fair bit of kayak fishing in the past so I'm used to getting places under my own steam, carrying the appropriate safety kit and general anchoring principles. I've also done my fair share of accepting that the tide is too swift for me to work against and waiting it out
having an engine will be something of a new experience though (although I'm used to working on cars and bikes historically.)
I just don't like the idea of being a mile offshore and flaming engine refusing to start!

prairie tuber 25 August 2011 10:54

Generally, you don't see twin outboard set ups on SIBs that are less than 5m long. Where you do see twin OB setups on these larger SIBs are with military or commercial applications rather than for civilian use. You won't get nearly as much propulsion from two 5hp outboards as from a single 10hp outboard.

With 2-3 adults in a 3-4m SIB, a 10hp outboard would be marginal and might not get you on plane. Most 3.5-4 meter SIBs will have max hp ratings much higher than 10hp, more like 50hp for some of the more stout 4.0m SIBs. I would be wary of the construction quality of a 4m SIB with a 10hp max rating.
If you have the space inside, you could take a 3-6hp outboard along as an auxillary. You would likely find that a 3hp outboard will crawl you back to shore in calm conditions but be useless in a current.

White2505 25 August 2011 11:02

I'm looking at around 3m length as my ideal starting point. only looking to carry 1 normally with occasional 2 and three person trips.
Not figuring on taking on large swell/current combinations. mainly looking at the safety angle which judging by the posts isn't the issue I though it was as the engines sound like they're fairly reliable if looked after. also looking to do this on a sensible budget so brand new 10hp outboards are out of the question!

prairie tuber 25 August 2011 11:08

As for self propulsion in a SIB, their width makes them pretty awkward for that. If in shallow water (less than 2m) a long push pole is by far the most effective. Assuming deeper water, if you are alone, oars are the only way to self propel. Paddles will work if there is a least 2 of you (preferably more) each with paddles.

frankc 25 August 2011 11:09

In addition to the weight of two outboards, you need transom width. The advice of a VHF and good anchoring system is good, but you also may want to carry a sea anchor if you are really concerned, and a GPS would be invaluable to tell the rescue folks where you were.

Give the rescue folks your position and throw out the sea anchor. They can probably plot the position vs time by taking into account the currents in the area where you are when you report the trouble.

Have been using outboards for 40+ years, and only had two occasions of having to depend on wood propulsion to get home. One was a failed lip seal which had given good warning before failure and a shear pin without tools to change it. It is unusual for a two stroke to let you down if you give it proper maintainance.

prairie tuber 25 August 2011 11:17

Quote:

Originally Posted by White2505 (Post 417279)
I'm looking at around 3m length as my ideal starting point. only looking to carry 1 normally with occasional 2 and three person trips.
Not figuring on taking on large swell/current combinations. mainly looking at the safety angle which judging by the posts isn't the issue I though it was as the engines sound like they're fairly reliable if looked after. also looking to do this on a sensible budget so brand new 10hp outboards are out of the question!

If you come across a gently used 10hp 2 stroke at a fair price, it will offer some advantages over the newer 10hp 4 strokes - particularly weight and possibly less maintenance costs. Reliability should be good fore either 2 or 4 strokes.

Are you planning to assemble & disassemble the boat with each use? If so how much outboard weight are you comfortable handling? For the same weight, you can get a more powerful 2stroke than a 4 stroke. Are there any differences in the boat regulations in Britain depending on whether the boat is powered by more or less than 10hp (as is the case here in Canada)?


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