Spare engine mounting help needed

Flanker · 19 September 2002, 14:14

I am having a 9.8hp 2 stroke put on a 6.6mtr RIB as a spare. I understand that I will need to get a long shaft model, and that it should have a 'High thrust prop' (you would never believe a week ago I knew nothing about boats). I have also heard to my dismay that my plan to also use the 9.8hp on a SIB is out of the question because of the long shaft, unless I raised the back bit of the SIB or whatever with a 'raiser' (if that is the term) which would then give the correct speed but knacker the boat quicker.

My concern is that apparently these RIB's bash about a bit, I was told that a good idea is to put the engine on back to front and then strap the bottom bit to the transom inside the boat, this should stop it bashing about.

I was also told that a 5hp could push 2 tons and that as the 9.8hp would not get a 6.6mtr on the plane, and there is only a maximum speed that the hull will go off the plane, that it would be a waste.

Boy this is a nightmare, but I am determined to learn from you lot, my brain is hurting and I have not even started my RYA 2 course yet.

Sorry to clog up the site, but any wise suggestions on this??

Pete (nearly done)

DJL · 19 September 2002, 14:48

The problem with having the engine mounted back to front is that when you need it you have to take it off the transom and turn it round; lifting a 9.8HP engine in rough seas won't be that easy. I jam a piece of wood on the end of a piece of bungy cord into the tilt mechanism to stop it bouncing.

As to the size of the engine. While at the boatshow on saturday looking at a 27ft Targa (large boat - Picture ) they suggested that a 6HP be used as an aux engine and I can't imagine that it would go anywhere with that. I have a 4HP on my 4.7m RIB and get around 6kts at WOT. If you can I would try any engine before buying, I got alot better performance from a 4-stroke 4HP than a 2-stroke 4HP from the same manufacturer! plus having a 4-stroke allows me to run it off my main fuel tank.

You need to check the height of your trasom to see if you need long or short shaft. I use a short shaft on my RIB and it fits perfectly with the anti cavitation plate a few mm below the hull.

Daniel

badbaws · 19 September 2002, 15:03

I have tried with a 2hp Honda on a 4 metre...there is not alot of room on the back end...I got it on only to find after 2 hours it was just about to fall off...I don't have a dedicated bracket...just strapped it on...Possibilty is to get an adustable height outboard bracket that usually has three or so settings...Boling thisa to the transom allows engine height to be change...
2hp pushed RIB along albeit at only about 4 knots...
Used to have a Shetland 535 with a 70's 4 hp 2 bladed 2 stroke that did 6.5 knots....
I would say on a 6 metre boat 5-6 hp is a good size...two stroke generally has more power...(controversy to follow!!)
I was at gym when u phoned last night did not get message till 11pm...
Tohatsu 90hp is the slimline one so hopefully there would be enough room on transom for Aux...
Alternately make an attachment on the console jockey back rest...as in some race ribs the Aux engine is inboard... then mounts on back end if needed...also puts the weight in the centre of the boat..
As for sunday...Not sure what am doing yet...so if u have someone else that is best...If not ring on saturday will have mobile on all day and shall see if am free Alex

badbaws · 19 September 2002, 15:08

Does it have to be a Tohatsu...6m...
There is a nice Ribtec 6 metre on the boats for sale page...twin 60hp...Better relaibility get u home.....
Money saved allows for more modifications to get best setup...
Ribtec are a good breed...
Alex

Brian · 19 September 2002, 15:14

My 2p's worth.
Don't bother with an aux. more pain etc than it's worth (banging about, two fuels, takes up room, more things to go wrong/buy/service etc).
Why do you need it? In case engine no1 fails?
Get yourself an anchor, a sea anchor and a VHF.
If main fails,shout for help. If in immediate danger, anchor and shout louder.
PS Longshaft works fine on a SIB, just take care when opening the throttle thats all.

Alex Brown · 19 September 2002, 15:25

One of the guys where I work always reckoned on something like 1hp per metre with aux engines...... but, my parents Hardy (6.4m) only had a 4hp 2 stroke on the back, which propelled it along just fine in most weathers.

I'm looking at getting a 6m Humber in the next month or so, and was hoping to stick a 4hp 4 stroke on the back, but I'm not sure as yet whether I'll have to put a proper aux bracket on the back, or if the engine will mount directly onto the transom (which I'd prefer). I'm actually hoping Humber will know the best solution for this.....

-Alex

(first post - yay!!)

Daniel · 19 September 2002, 15:31

I had a 6hp, but it was a pain in the ar** whenever there was a slight ripple - tried to fall off, tried to jump out, bounced on my foot...then i changed to a 3.3hp, BUT to be honest i rarely take it with me (silly really) and go with Brians option...

I have two VHF's, two sea anchors, two anchors and a VERY loud voice - oh, and i buy the lifeboat crew beer when i see them in the pub!

Oh, one final comment - ribtec w/ twin 60's - nice setup and worth considering...

batfalcon · 19 September 2002, 16:29

I use this method in order to hold the engine really unmovable. This way the engine is mounted on another bracket with it's leg strapped on it's working place. Of course I have to move it from the one bracket to the other IF something goes wrong with the Merc. (Never so far).

Flanker · 19 September 2002, 16:51

Great idea, but see my last post re on the rocks

Pete

Nigel · 19 September 2002, 16:57

Hi,

On my RIB, I have found that to mount the wing motor (a Malta - quite adequate) in the bow on a specially made bracket helped (see picture). I really wouldn't feel comfortable going outside the Solent without an auxiliary.

Re your other thread - I also find a Hydrofoil on the main engine gets the boat up on the plane much quicker - an advantage to be able to plane at 10 knots in Portmouth harbour

Rgds

Nigel

Daniel · 19 September 2002, 18:12

Nigel,

Have you had her re-tubed? They look very shiney! Any idea of the year (i ask because i have a DS 18 too!)

DM · 19 September 2002, 19:27

I know this is of no use to flanker now but with ref. to auxiliary engines, I feel that most donkeys are not big enough. Some will disagree, but I have always found a bit of extra power never goes amiss. From my own experiences I use an 8hp shortshaft on a three position bracket which is bolted to the transom. The wooden mounting plate has two circular recesses cut out for the mounting lugs . The tightening handles are then tied together with a cable tie so they cannot come undone. I would recommend that even if you have no room on the transom, carry the engine in the boat. Its easy enough to make a mount out of two pieces of 3/4 marine ply glued together and bolted to a backrest. It also pays to try and see if you can lift it onto the transom in any sort of chop. Also if your main is 4/ or 2/ keep the donkey the same. Its personal choice whether to carry an auxiliary but I wouldn't want to activate an RNLI resource for a simple mechanical problem. As for engines, the yamaha malta is a really punchy lump for its size and ideal for a back up on the average 5m. This brings up another question. Should the RNLI charge for mechanical breakdown tow ins where there is no immediate threat to life.

Flanker · 19 September 2002, 20:05

I am depressed at the moment, it is the first time I have had an interest that I found interesting, make sense? I think it is the sense of humour that I like as well, unlike the yacht types. Anyway I understand that others read these threads so I will keep going until I get a reply tomorrow re my complaint to them.

Anyway the 9.8 Tohatsu is apparently the best weight to power ratio engine, hence my choice. I can't say any more as I am getting choked up thinking of the boat I got excited about buying(just a joke)

Pete

DJL · 19 September 2002, 20:07

The RNLI should charge for mechanical breakdown tows, but it would never work.

You would end up with the RNLI crew taking credit card details as the stricken vessel blows onto the rocks. What happens if they don't pay? Do they get left there.

I hope that anybody who gets rescued by the RNLI would give a large donation anyway, whatever the emergency. I would!

Garygee · 19 September 2002, 21:09

Hi folks

Its quite interesting that only the RNLI are considered for giving a tow.
We are all out there toghther and in you pardon the pun in the same boat.
If I heard a call for help due to mechanical breakdown I would not hesitate to offer a tow, even if it meant cancelling my trip. One day it might be me and i hope that there would be many people other than the RNLI to lend a hand.

If everyone was willing to provide, where they can safely for other boats the RNLI could be left to handle real emergencies.

I see this from a both sides in a way being a mountaineer who often relies on others for help if needed and also a member of a mountaine rescue team providing help. I dont belive help at sea is any different, if help is needed and you can help, do so as next time it may be you.

However it does not matter how much help is at hand there is never any excuse to go out ill equipped or undertake things beyond your boats of your capability.

Regards Gary (on his soap box) Greenwood

DJL · 19 September 2002, 22:03

I am always willing to help others and do quite freqently. The last was a wind surfer out by cowes. If i'm close enough to help I always will.

Trouble is there are days when there arn't any other boats out and the RNLI would be the only people around to help. I went out a couple of weeks ago on my own in the afternoon, I only saw one yacht while crossing from Poole to Yarmouth.

To be honest I don't think there are any people on this forum would go to see without being 'properly' equipped. It tends to be the people who try and start their engine while tilted right up and attached to their car on the middle of the slip after spending 20mins doing the years servicing with 2 spanners and a screw driver!

Brian · 20 September 2002, 13:40

I wonder what percentage of calls for help, VHF or otherwise, are actually responded too by a lifeboat?
I have towed other boats to safety and been towed myself.
Never yet had to call on the emergency services (touch wood).
The secret (if there is one) is to be well prepared and to cruise in company (i.e. relying on yourself first and your mates, second).
I am also told that unless conditions are "dificult", the Coastguard may be refused an lifeboat callout by the RNLI Launch Authority on the grounds that a commercial tow can and ought to be arranged instead.
PS That does NOT mean that you should either delay or abandon a call if you feel it necessary.

Garygee · 20 September 2002, 20:13

Hi folks

Hope the previous post was not taken the wrong way.

This is a subject close to heart as all be it on the mountains I see 50 idiots in trouble, wrong gear, wrong place etc for every person who did everything right and was just unlucky.

I think people on RIB Net are those who are interested in there chosen interest, want to do thing right and take the care and preperation needed to be safe and are only happy to provide help to others. The sort of people I would want out with me

I am however sure that there are many people out there who think, it will never happen to them and who needs saftey gear anyway thats what the lifeboat get paid for. Well it will happen sooner rather than later it this attitude is taken and thats not what the lifeboats get paid for as they dont get paid.

Its a pity that most of them will never bother to read this and think. As the people reading this have already taken a interest, thought and are hopefully doing things right.

Regards Gary