Is this right, 15hp backup?

[JJ7893]

Hi all, my dad and myself just bought Ogwen2 over the weekend and having fun with her already and she not even on the water yet!

Right I come across a problem, The back motor was stolen a while back so we going to replace it with something suitable, I have done a little googling and come up with peeps saying we would need a 15hp outboard. Ok if that is right but I would have to stress that we already have a 1988 Johnson 70hp motor mounted to Stuart Stevens weekender. Now we know 15hp is already heavy is this going to cause problem's on the back with all this weight on the trasom? Please bear in mind that we will be spending most of the time on the Menai Straits.
The last one was a very small one and my dad has already seen it in action and it something he don't want a repeat of.

If it going to cause problems what would you recommend? We decided we will not part with the 70hp so it have to be something suitable for both the craft and engine.

Many thanks JJ

 

[[2068]]

I would have thought something like a Merc 5hp 2-stroke would do the job. Weighs about 20kg, and has enough ooomph to move you against some sort of current. Uses an inbuilt or separate tank.

 

[BrendanS]

The problem is going to be the Menai Straights. Moving against 'some sort of current' isn't going to be realistic a lot of the time.

Kawasaki, resident of these forums, should be able to give suitable advice, as he knows all about the straights, and a lot about motors too.

 

[JJ7893]

Brendan, I have once spoken to Kawasaki before just before we bought the boat. He is a nice chap, This is why I asked because the Straits is a very strong current area, so would the 5hp not be up to the job?

Thanks for the comments so far.

........JJ

 

[BrendanS]

I've sent him a pm, so hopefully he'll look in and advise.

 

[[2068]]

5hp won't get you upstream against full flow, but is that what you want? When we had a single engine, the backup o/b was enough to keep us off the rocks and anchor, not a get-you-all-the-way-home.

 

[JJ7893]

We need a back up engine to get us home if needed, So I did think the 5hp was too small. But if we did fit an 15hp will it drop the boat a lot lower?

Thanks Brendan, I had sent him another message couple of days back just to say we went and bought the boat. But I forgot to ask about the engine and I did not wanted to bother him as I not had a reply back yet.

........JJ

 

[[2068]]

Merc 15hp two-stroke weighs about 35kg, if you can get hold of one.
15hp four-stroke, more like 60kg

 

[JJ7893]

Cricky! I think it would be best to stick to 2 stroke engine, I was thinking of getting another Johnson so if we do break down all we would have to do then is swop over the fuel line. That is what I was thinking of.

......JJ

 

[JJ7893]

This is how much space we have when it sits on the water as you can see the waterline. I not been or seen it when loaded so I have no idea how low it goes down. I also know it goes lower again when it going.

........JJ

 

[AndieMac]

Can you borrow a long shaft 15 to see what you think?

What size is the boat?

 

[AndieMac]

You may get away with a long shaft 8.

 

[JJ7893]

It's 18.4ft long. We don't know many boaters about they are more in to yachting rather than motor boating. I will double check with my dad and see if he knows anyone.

.......JJ

 

[jfm]

I'd have thought you want 9.9hp to get you home. 2 stroke much lighter, so try to find one secondhand.

To see how the boat handles the weight, just ballast the boat at the same corner and take a look how it sits. Eg use a person: petite woman = 50kg

Ref getting another johnson so you can swap the fuel line: I wouldn't worry about that. Fuel line connectors are cheap as chips, so you can get a dedicated fuel line for the second motor. Also, some manufacturers use the same fitting. I can't remember exactly, but I think yamaha and Johnson are the same, for example? Mercury has its own unique bayonet. Anyway, no worries, just make up a fuel line for the second engine if need be

But regarding fuel, does your 70hp Johnson run on premix petrol and oil? If it does, you MUST buy a 2 stroke auxilliary engine that will run on the same mix. On the other hand if your Johnson is autolube (so that you don't add the oil into the petrol tank) then you need to get an auxilliary that will run on pure petro (autolube or 4 stroke)l, or carry the correct oil and measuring device to add the oil to the petrol. You get the idea - just work out the ifs and buts

Finally, you will have to add a transom bracket to hold the second engine, on that transom

 

[AndieMac]

Sometimes the cause of the failure in the main motor is fuel related (excessive water, crud, sealant, rust, etc.) so having a completely seperate fuel supply in the form of an aux. tank for the little outboard could improve the safety margin.
They are a bit of a pain to fit somewhere on an 18' boat, but could be an important factor if main tank becomes contaminated.

 

[JJ7893]

The 70 has 2 tanks one petrol and the other oil. So I don't have to pre mix the fuel. We have 3 fuel tanks for the boat and they will be filled when being used. So I could find an outboard that run in the same as 70hp (Autolube) or will that be a little harder, We not going to go and buy a new one as we also going to buy a dinghy and an outboard for that as she going to be moored on the straits so we need an other much smaller outboard. My Dad is sorting that one out and my job is to find a suitable backup

.........JJ

 

[moonraker 36]

johson 9.9 2stroke..
the earlier engine's you can upgrade by putting the 15hp carb on it..then it becomes a 15hp!!
CHECK OUT YOUTUBE..

(but i dont think their is much difference in weight between the 9.9 and 15hp
basicly the same engine)

it doe's look abit tight to fit a large aux o/b on that transom ?

 

[JJ7893]

Cheers moonraker, I will look it up and see if I can find a 2 stroke Johnson 9.9 and a carb to go with it.

.....JJ

 

[moonraker 36]

put in you tube..
9.9 johson outboard 15hp carb .
and afew post's come up

 

[Kawasaki]

Back in a bit JJ