what engine?

dorsetdarren · 11 September 2009, 20:16

ok i got my 310 fastroller,will be carrying 2 adults (11 stone + 9 stone ) 2 kids 4 + 8 yrs. i think either a 8 or 10 hp 4 stroke, what about 2 stroke options?not so keen on second hand though as i wont know what is good or not until too late. we have a rooteq trolley so weight not such an issue although lighter would help.looked at honda 8 + 10 but pricey and heavy,are they worth paying for or are there any other options i should be looking at.cheers for any help

codprawn · 11 September 2009, 20:19

A nice 9 or 15hp 2 stroke - they are the same weight usually!!!

Believe me a similar 4 stroke is HEAVY.

I have a 15hp suzuki 4 stroke - it's great but awkward to move - it's not just the sheer weight but the curvy shapes and no carrying handle make life really difficult.

MikeP · 11 September 2009, 21:40

I'll bite on this one then....

We've got a four stroke; I can see that larger HPs would be thought-provokingly heavy.

Why are two strokes lighter ?? (are they half as heavy ;-) )

More to the point, from what I've read, you need to fiddle about with oil/petrol mixing for two strokes. Obviously not an insurmountable problem, but does it become one of those pain in the ass things you'd rather avoid ?? Four strokes are obviously the newest big thing for a reason...... anyone got any thoughts ??

codprawn · 11 September 2009, 21:49

Four strokes are great if you don't have to carry them around!!! Easier to start - less fiddling with and more fuel efficient under 1/2 throttle.

That's why things like chainsaws etc are 2 strokes - much lighter in weight.

No 4 strokes aren't twice the weight - but an extra stone or so for a small engine when you are carrying it makes all the difference!!!

Poly · 11 September 2009, 21:58

Quote:

Originally Posted by MikeP

More to the point, from what I've read, you need to fiddle about with oil/petrol mixing for two strokes. Obviously not an insurmountable problem, but does it become one of those pain in the ass things you'd rather avoid ?? Four strokes are obviously the newest big thing for a reason...... anyone got any thoughts ??

The reasons 4 strokes are now more prolific is down to EU emissions regs.
Mixing fuel/oil was/is not really a major issue. A minor inconvenience, and slightly messy. Larger engines were tending to have automatic mixing systems built in anyway.

Other than weight - the major pain with supposedly small portable 4-stroke outboards is the need to store them a particular way to stop oil "draining" into the cylinders.

m chappelow · 12 September 2009, 10:08

yes i use an 8 hp 4 stroke but a few weeks ago we tryed it out with a 15 hp 2 stroke weight of the 8 made a big difference ,think another difference is that with 4 strokes they take a while to proper warm up ,,with mine about 5 mins where as a 2 stroke only a coulple of mins ,,,though one big advantage with 4 strokes is they dont oil up if idling for a long periods of time and you can just pop it in gear and they dont cut out as 2 strokes usually do,,,takes some getting used to if all you have run for the past 35 years are 2 strokes ,,lol ,and fuel wise they are wonderfull .also they seem less noisy i can just about hear the vhf now when running ,

m chappelow · 12 September 2009, 10:39

Quote:

Originally Posted by MikeP

I'll bite on this one then....

Why are two strokes lighter ?? (are they half as heavy ;-) )

anyone got any thoughts ??

i suppose the weight difference is down to the fact 4 strokes have extra mechanical bits for a start unlike 2 strokes which dont have ,,,valves ,springs ,cam shaft , tappits,,heavier cylinder head ,then theres extra pullys for cam belts , an oil sump and oil pump ,and say a litre of oil ,then extra nuts and bolts ,

matt h · 12 September 2009, 14:41

Quote:

nice 9 or 15hp 2 stroke - they are the same weight usually!!!

Believe me a similar 4 stroke is HEAVY.

as codders said, dont bother with a f/s too heavy, have been there, 10hp t/s will be the best bet, craft also a bit small for the amount of people really, it will be a wet ride!!

dorsetdarren · 12 September 2009, 14:54

Quote:

Originally Posted by matt h

as codders said, dont bother with a f/s too heavy, have been there, 10hp t/s will be the best bet, craft also a bit small for the amount of people really, it will be a wet ride!!

why will it be a wet ride ? because it will sit lower in the water due to weight?

Locozodiac · 12 September 2009, 15:06

Go for the max engine the sib can handle (look sib's plate info) a 2 strokes would be better, about 10 less kilos compared to same 4 strokes versions. And mixing gas/oil is not a big issue.

Happy Sibbing

Fenlander · 12 September 2009, 15:11

My thoughts as a user of a 3.2m Zodiac with Tohatsu 9.8hp 2-stroke.

As said your craft will be a bit small for the load you intend to carry. It will take more than 10hp to plane 4-up so you really need 15/20hp for comfortable performance. Planing 4-up in such a small craft with a powerful outboard has the potential for problems... with that many folks on board there is a real danger of someone getting bounced out.

If you accept you won't want to plane then 6hp max will be plenty so lower cost and less weight.

It is true that for an inflatable around 3m a 2-stroke is ideal compared with a 4-stroke. My Tohatsu 9.8hp weighs the same as a 4hp Mariner 4-stroke.. or looked at another way 22lb lighter than a Mariner 9.9hp 4-stoke... makes a big difference to carring weight as well as load on the transom.

Mixing fuel isn't an issue...modern fuels mix easily and have minimal exhaust smoke. Ref starting... my Tohatsu was tested by a magazine against a whole range of 10hp 4-strokes and it was the only one the testers wife could start 1st time. My 12 & 14yr old girls find it an easy 1st time pull.

I wouldn't worry about a newish used motor. If you go for one of the last 2-strokes made it will be less than 4yrs old and often they have very low hours... some only just being run in. It is a fact that people just do not get out on boats as much as they plan when buying! One tip is to buy from an inland dealer where it has likely been used for a river dayboat and never seen salt water.

Here is my immaculate Tohatsu as it was delivered.

Came from a small Inflatable/Outboard dealer I found on the internet. About 18mths old at the time with just a few hours on it. About 60-70% of the new cost. In truth it may be even more reliable than a brand new 4-stroke as it has less parts to go wrong and no modern high-tech electronic stuff. It is so economical anyway the fact that a 4-stroke may be better isn't an issue.

I completely disagree with the old notion that 2-strokes will oil up when trolling along and stall when you try speed up. Neither my Tohatsu or my 24yr old Mariner 20hp on my other boat do this. With the correct spark plugs (replaced at each years service) and exactly the right fuel mixture with quality oil it's not an issue.

Hope that helps.

David

dorsetdarren · 12 September 2009, 15:29

Quote:

Originally Posted by Fenlander

My thoughts as a user of a 3.2m Zodiac with Tohatsu 9.8hp 2-stroke.

As said your craft will be a bit small for the load you intend to carry. It will take more than 10hp to plane 4-up so you really need 15/20hp for comfortable performance. Planing 4-up in such a small craft with a powerful outboard has the potential for problems... with that many folks on board there is a real danger of someone getting bounced out.

If you accept you won't want to plane then 6hp max will be plenty so lower cost and less weight.

It is true that for an inflatable around 3m a 2-stroke is ideal compared with a 4-stroke. My Tohatsu 9.8hp weighs the same as a 4hp Mariner 4-stroke.. or looked at another way 22lb lighter than a Mariner 9.9hp 4-stoke... makes a big difference to carring weight as well as load on the transom.

Mixing fuel isn't an issue...modern fuels mix easily and have minimal exhaust smoke. Ref starting... my Tohatsu was tested by a magazine against a whole range of 10hp 4-strokes and it was the only one the testers wife could start 1st time. My 12 & 14yr old girls find it an easy 1st time pull.

I wouldn't worry about a newish used motor. If you go for one of the last 2-strokes made it will be less than 4yrs old and often they have very low hours... some only just being run in. It is a fact that people just do not get out on boats as much as they plan when buying! One tip is to buy from an inland dealer where it has likely been used for a river dayboat and never seen salt water.

Here is my immaculate Tohatsu as it was delivered.

Came from a small Inflatable/Outboard dealer I found on the internet. About 18mths old at the time with just a few hours on it. About 60-70% of the new cost. In truth it may be even more reliable than a brand new 4-stroke as it has less parts to go wrong and no modern high-tech electronic stuff. It is so economical anyway the fact that a 4-stroke may be better isn't an issue.

I completely disagree with the old notion that 2-strokes will oil up when trolling along and stall when you try speed up. Neither my Tohatsu or my 24yr old Mariner 20hp on my other boat do this. With the correct spark plugs (replaced at each years service) and exactly the right fuel mixture with quality oil it's not an issue.

Hope that helps.

David

thanks david i was i bit worried about bouncing a kid out and i think our reasons for getting a boat is to cruise around rather than worring about getting on plane.so my thoughts were to get a 4 stroke 6hp lowering the coast and weight.i think ill look for a suzuki 6hp or mariner/mercury or even a 5hp honda bf5. if i go slower will we get less wet as i dont think this is what the family want.up and down the estuarys and along the coast when its not choppy sounds ideal for us.
im a bit concerned about the size of boat as people keep saying its a bit small,should i sell it and get a honda 3.2 / 3.8 as it has bigger tubes aiding boyancy

Fenlander · 12 September 2009, 15:57

On the sea we only use the Zodiac 4-up for short hops. We're carrying a bit more weight than you with adults weight total 23st and two kids 12 & 14yrs... plus small dog.

As this prevents planing then even in a small chop water tends to slop up the tubes and you get a wet backside (we all sit on the tubes). Dump two people and you can plane and it is less wet as the water tends to spray away from the boat as the tubes skim the water.

At the moment we are talking about upgrading to a 3.4/3.8m SIB for next year.... but that will really mean a bigger engine... then perhaps a trailer rather than car booting it as we do now... and so it goes on!

David

matt h · 12 September 2009, 15:57

Hi darren

Quote:

why will it be a wet ride ? because it will sit lower in the water due to weight?

yep

really for what you want to do with it and what you want to carry is a bit on the small side, ideally a 380 up and a 10/15 hp t/s for a reasonably safe day out, Sibs are a laugh a minute with the right one

Fenlander · 12 September 2009, 16:04

Re the water slopping over the tubes. As well as the issue of being low in the water when laden it's the shape of the tubes. A "normal" grp boat will likely have hull sides that lean out towards the top and a rubbing strake all around the top plus greater freeboard. So small amounts of water just do not slop in.

The shape of inflatable tubes actually encourages water on board at slower speeds.

If it is a bit choppy when we're laden we sit so it's deliberately bow high at about 6mph and that keeps the wet to a minimum.

David

Locozodiac · 12 September 2009, 16:07

A 310 sib can carry about 550 kilos max load, if it doesn't exceed (4 passengers weight) will be ok for your intended use, check sib plate, a Tohatsu 2 strokes 9.8 will be an excellent performer for that size sib, portability and reability. To buy a small first engine is a bad investment, go bit larger. Can be used on future 320/330/340 larger sibs.Tohatsu 9.8 has same block as 6 & 8 models and weights the same 26 KG.

If tubes are 38/40 in diameter will sloop more water than 42/45 higher tubes, will depend also on the kind of rubstrake that sib has, lipped ones are far better than plain ones on sib performance.

Happy Sibbing

matt h · 12 September 2009, 16:43

some of the sib Combiations ive had i will list below, had quite a few just because i have won them on Flea Bay at really good money.
first one i had was
QUICKSILVER 430 ALLYFLOOR with a new Tohatsu 40c short shaft outboard, fantastic fun,ballistic but hard going after a while and a bl--dy pig to put away, all those side sections, took 25/30 mins and with cold wet hands (at the time)
next one was a new seago 270 (got given it) with a new Yamaha 6 hp two stroke, again great little craft, two was more than enough in it, 4 got in once, blimey, all soaked,, but because of its flat floor, was useless in any sort of small ripple /wave, two would be more enough, rated for 4 i think,

next one was a Avon 340, with brand new Mercury 9.9 f/s, because of the lying down (when loaded in car)and weight issues, handled like a pig, could not get the floor hard enough and wallowed like a deflated waterbed, absolutely rubbish.
could not really get on the plane as prop cavitated and a large airpocket would pass underneath, so would have to sit on the flat floor to eliminate that problem, hard going after a while and would remain wet and slippery inside, again, recommended short shaft was fitted.

next one was a seago 320, (won it on flea bay for £200, brand new) put a yam 8hp two stroke,as shown, engine was superb ,really, all day for a tenner of fuel, two up was a great small craft, once put four in it, 11 stone, 8 stone, 12 stone approx and 5 stone approx, not enough to plane,also turned steeply and nearly capsized, very wet as the water just rolls over the top, again, flat airdeck, very wet,slippery etc, easy to deflate and put away tho,

next one, Bombard aerotec,380 with Suzuki 15 four stroke, engine so blo-dy heavy, 3 mins to assemble and pump up, awesome boat, economical engine but really heavy, 2 up and you flew, felt safe and is a lot of fun, sold the engine and put a Yamaha 15 t/s, wheat a awesome set up, safe, fast, dry due to the way the airdeck is laid out, the water just drains away to the bottom and with a grippy airdeck easy to stay dry and comfortable,

next one, Bombard 380 with a mercury 15,, this was the best little inflatable i ever had,the engine tilt mechanism isnicer to work than the yam.was such a fantastic well balanced SIB, sold it to a chap on Ribnet, i think he's loving it, with a Bravo 12 electric pump ( we actually timed it) with everything laid out we could be on the water in just under 5 mins, and also packing away was about 6 mins.
pictures enclosed

matt h · 12 September 2009, 16:51

seago 320 with yam 8hp or without!!

Flyguy · 14 September 2009, 13:14

If I had to lug a 4-stroke about each time I took the boat out I would probably not bother half the time. 2-stroke yams and tohatsu's are perfect for 3m SIB's. They get you on plane in a couple of seconds, they are reasonably quiet and economical and the point about mixing fuels isn't an issue.

Fenlander, that is a very tidy 9.8 you have there. Have you tried it with the Dohl Fins?

Fenlander · 14 September 2009, 20:13

Yes it is a nice example thanks. Bought it from a dealer at retail money after spending months looking at the cheaper bargains on EBay which were either at the other end of the country or total rubbish.

I haven't tried the fins. They were fitted when I bought it but I took them off for easier storage and despite taking them with me to the coast several times have never tried them. To be honest the pair I tested on my 13ft GRP boat had a negative effect on its performance and handling so I'll probably never bother on the Zodiac. Anyway it handles and goes exactly as it should without.

Other folks like what they do which is OK by me.

David