AUX on Osprey

Chris · 28 April 2007, 09:00

I picked up a very tidy Yamaha 4HP 2stroke yesterday and am now trying to work out the best option for mounting it. Initially I toyed with the idea of having it mounted on the A frame when not i use however having hefted it up to the Aframe I can't say I would fancy having to try and lift it off the A frame and onto the transom in anything but flat calm.

So I think that the point of having the engine on the transom so that its ready to go is a valid one, I am lucky in that the Osprey is quite a wide boat so has enough space on the transom for the Aux also the transom is a substantial one being over 2" thick at the top, however I need to do a little transom surgery to get it on. As you can see below there is a lip that would need to be cut away at the bend. Out of interest what would be the best tool for this job? an angle grinder?

I have looked at the idea of an AUX bracket however I think that if I can get the engine on the transom then why bother with a bracket that could break, also I think the bracket would stand the engine further off the transom which will get in the way of the main engine.

Once I have cut away the lip what would I do to water proof the exposed wood of the transom?

Finally is the Yamaha bracket going to last and will the mechanism that holds the engine out of the water also last or do I need to do some thinking about how to brace the engine when not in use?

Thanks Guys

Chris

vince · 28 April 2007, 09:37

Mornin Chris. It seemed an awful lot of work for us to have to cut the transom, as ours is similar to the construction on the osprey, then having to re-do the gel coat to keep water out etc. We went down the bracket route as it is a lot easier. Just make sure you get a decent bracket to start with, and you should be fine. Get one with bolted hinges rather than welded ones as these have been known to fail!! ha ha. If using a bracket, you'll find it dosnt foul the main motor as long as positioned correctly. Also, the brackets are easy to use as they are spring loaded making the aux feel a bit lighter when lowering/ raising, the bracket takes a lot of the work out of it!

Pete7 · 29 April 2007, 12:16

Chris, you need to get the prop below the transom or you will loose a lot of drive and be disappointed. Tried a 4hp short shaft, dismal, 5 hp long shaft quite good giving 4-5 knots. From experience a short shaft isn't long enough on a Viper to clear the transom. The problem with the brackets is even the 20 hp ones wobbly and look flimsy at 30 knots so you end up with a lashing to the A Frame just incase it all gives way.

Will the aux fit in the rear bench seat ?

Pete

Chris · 29 April 2007, 18:36

Pete, I have taken some measurements and the prop should be about 2/3 below the bottom of the hull so it might be OK?

I picked the engine up for a v good price so if needs be I can resell it and look out for a longshaft.

It won't fit in the benchseat and also I am planning on keeping 2 x 25 litre cans of fuel in there.

I am definately going to go for mounting direct to the transom as it will fit nicely and there is then less bracketry to fail.

I tempotarily mounted the engine today it is sitting higher than it will once I have taken off the lip on the transom however you can see how it will clear the engine at full lock.

Chris

Chris · 29 April 2007, 18:52

Here are some pics I took earlier aas you can see the only place at which the main engine catches on the aux is on full lock and about half way up. Otherwise both engines can operate freely without catching on each other.

Jon.esp · 29 April 2007, 21:04

Chris
I note that you have an A frame
Do you have any isues with the tiller of the aux fouling the A frame?
I have and there has been some sugestions on the thread Aux on a Rib which I don't know if you have noticed. I will watch this space to se how you get on.
Jon.

Chris · 30 April 2007, 07:50

Jon, I dont have a problem with the tiller on either the A Frame or the engine. I get about 45degrees movement either way.

Chris

bedajim · 30 April 2007, 09:08

Hi

I've mounted mine like this works ok you have to lift the tiller a little for the Aframe but with the aux tilted there's plenty of room normally

Chris · 01 May 2007, 17:15

Took the angle grinder to the transom today and trimmed off the lip the outboard fits on a treat and I reckon I should have enough Prop below the Transom.

There seems to be enough side to side movement even without lifting the tiller if I need more I can always lift itand get a little bit more.

What do you think Pete7?

Chris

Pete7 · 01 May 2007, 19:57

Quote:

Originally Posted by Chris1573

What do you think Pete7?Chris

Only one way to find out, but I recon 3 knots tops.

Chris · 01 May 2007, 20:55

Well Ive done the hard bit which was cutting the transom, if this doesn't give me at least 5 knots it's onto ebay and then i'll be looking for a 5hp longshaft or do you think Ill need to go bigger, I just wanted to keep to the single pot smaller engine as once you go into the realms of 6HP plus its 2 pots and more weight?

Chris

BogMonster · 01 May 2007, 21:54

Quote:

Originally Posted by Chris1573

Well Ive done the hard bit which was cutting the transom, if this doesn't give me at least 5 knots it's onto ebay and then i'll be looking for a 5hp longshaft or do you think Ill need to go bigger, I just wanted to keep to the single pot smaller engine as once you go into the realms of 6HP plus its 2 pots and more weight?

Chris

6hp Johnson 4 stroke long shaft (prop is clear of the hull) gives me about 4.3 to 4.5 knots on mine (Humber Destroyer 5.8m) but doesn't reach anywhere near max revs - I think it is hitting the hull displacement speed which at the square root of the waterline in feet, in theory on mine should be ~ 4.36kt. I have seen over 5kt on brief spurts but I think probably with "help" from water movement. I reckon your target is optimistic based on my (albeit limited) experience.

Pete7 · 01 May 2007, 22:05

Chris, if you want 5 knots I recon you need a 5 hp long shaft with an exhaust though the prop propellor rather than the solid one you have at the moment, but try it first.

Pete

Chris · 01 May 2007, 22:24

Quote:

Originally Posted by Pete7

Chris, if you want 5 knots I recon you need a 5 hp long shaft with an exhaust though the prop propellor rather than the solid one you have at the moment, but try it first.

Pete

Which 5 HP engines have a through prop exaust Pete?

Chris

Pete7 · 02 May 2007, 09:11

Quote:

Originally Posted by Chris1573

Which 5 HP engines have a through prop exhaust Pete? Chris

Chris, have a look at the 2 stroke 4-5 hp Merc, Mariner and Tohatsu engines. From memory I think the 5hp has the ability to switch from internal tank (little one on top) to external red tanks whilst the 4 hp doesn't.

http://www.boatsandoutboards.co.uk/view/F119838/

Pete