Back up engine.

[Mick.Roe]

Hi all, I have a 5.75m Osprey Viper with a 150hp outboard. I’m looking to get out to sea a bit more this year so looking to get a back up engine.
What size (hp) would anyone recommend to be best to be able to push the rib through any current ?
This would only be to use in an emergency.

[jakew009]

Originally Posted by Mick.Roe

Hi all, I have a 5.75m Osprey Viper with a 150hp outboard. I’m looking to get out to sea a bit more this year so looking to get a back up engine.
What size (hp) would anyone recommend to be best to be able to push the rib through any current ?
This would only be to use in an emergency.

I have a 6HP 4 stroke for a 7.5m rib, and frankly I think it would be as much use as a chocolate teapot in a true emergency.

The further out to sea you are the less use it would be.

[beamishken]

Originally Posted by Mick.Roe

Hi all, I have a 5.75m Osprey Viper with a 150hp outboard. I’m looking to get out to sea a bit more this year so looking to get a back up engine.
What size (hp) would anyone recommend to be best to be able to push the rib through any current ?
This would only be to use in an emergency.

Depends how much current your thinking of trying to punch. probably only going to make displacement speed of 6 kts ish unless you go for a ridiculously large aux to start pushing over the hump. If you have much wind or tide against you you might not be going far in a hurryagainst them . That said my view of a aux is it should be able keep you out of danger & keep you mobile & for that a 6 or 8hp would be my choice for your boat. Easy enough to store & lift about but big enough to move you to a place of safety which might mean going with the wind & tide to find safety rather than the direction you want to go but better than going nowhere & not being able to move at all

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[GuyC]

I've got a 15hp Mariner because that what goes on my SIB that I occasionally carry.

It sits on a Trem outboard bracket.

It makes a reassuring noise when its running but it's not all that effective in making the boat move.

I suspect that the shaft isn't long enough to get it below the bottom of the transom.

I think the rule of thumb is 1HP per metre.

[neil.mccrirrick]

Depends on what you hope to achieve with it.

I’ve a 6hp 4 stroke on a 6.9m Solent. It will never get me home but it will hopefully keep me off rocks and to a place where I can drop anchor

If you want it to get you back you need far more than a decent hp engine. You need separate fuel supply and enough petrol to get you back from your farthest point at displacement in the worst weather you might go out in etc etc

[Pete7]

Mick, since you won't be going more than displacement speed with a small outboard, you might look at the something like the Mercury sailpower 5 hp. There has been a series of these by several manufacturers for use on small day sailing yachts in the 20ft range.

The advantage is they may have a lower gearing but do have a bigger propeller for thrust rather than the high speed wizzy props designed for small sibs.

It you can get the prop down below the hull then a sailpower will provide far more drive to power you through the waves compared to an dinghy outboard.

The tricky bit is the shaft length. A long shaft on the transom won't be clear of the water when you have it raised and using the main engine. A short shaft not deep enough to get the prop down below the hull which is essential. An adjustable engine mount scary when travelling at speed with the main engine and one look back will have you reaching for a stout rope to secure it to the boat. We have resorted to mounting it on the transom but reversed with the prop inboard resting on the deck before now.

Pete

[beamishken]

With an aux at displacement speed you dont need the prop below the hull for forward propulsion especially if its on a rise & fall bracket which provides a set back . As long as its deep enough in the water to pick up its cooling water & not continuously buzzing up clear of the water its fine. Reverse operation wont be great but you'll unlikely be doing 3 point turns in an emergency. You can lock the aux in straight ahead & use the main as a basic rudder for steering

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[lakelandterrier]

If you are "out at sea" i.e. a long way from land, will an aux actually help in any meaningful way?

Would not a sea anchor to slow drift, good comms - fixed VHF +back up, and orange floating smoke pots and LED flare not be more relevant & effective than a small outboard which will maybe hold you against tide? And this outboard will need separate fuel etc... I am assuming UK waters where the are rescue organisations - Coastguard, RNLI etc.

If your boating is coastal / inshore in isolated areas with risk of being driven on to shores, then that would be different and an aux may make a real difference.

[Matt]

Originally Posted by Pete7

Mick, since you won't be going more than displacement speed with a small outboard, you might look at the something like the Mercury sailpower 5 hp. There has been a series of these by several manufacturers for use on small day sailing yachts in the 20ft range.

The advantage is they may have a lower gearing but do have a bigger propeller for thrust rather than the high speed wizzy props designed for small sibs.

It you can get the prop down below the hull then a sailpower will provide far more drive to power you through the waves compared to an dinghy outboard.

The tricky bit is the shaft length. A long shaft on the transom won't be clear of the water when you have it raised and using the main engine. A short shaft not deep enough to get the prop down below the hull which is essential. An adjustable engine mount scary when travelling at speed with the main engine and one look back will have you reaching for a stout rope to secure it to the boat. We have resorted to mounting it on the transom but reversed with the prop inboard resting on the deck before now.

Pete

Some wise words here ^^. I have a Johnson 5hp and I get 3.5 knots on it flat out. A different prop would improve this a little I think, but I've been through the parts manual and I can't find one (I would want a bit more dia and less pitch for more thrust)

I don't have it below the transom (too deep), but do have it as deep as possible and enough offset on the bracket so it doesn't ventilate or cavitate. It means reverse is no use, but fwd is fine.

Trouble is bigger becomes unwieldy - I want it on the transom so when I need it, it's there. No point in having a 15 hp motor that I drop overboard trying to attach to the transom.

So I view it not as a "get you home" motor, but only as a "get you out of trouble" motor, which I'm not entirely comfortable with. The trouble with a planing hull is they're just not efficient when running in displacement mode. Going up the hamble a few months back, I was running WOT and getting overtaken by yachts that clearly weighed about the same and were running at "cruise" throttle on their outboard - but all that churning of water behind the transom is a big fun sponge until you're planing.

(Thank you to the yachts that asked if I was OK - I was just running in "noise abatement" mode)

Don't forget about fuel, too. Bad fuel could be the cause of your breakdown. I carry a 12 litre (premixed, it's a 2 stroke) fuel tank for it - which I think'll give me at least 3 hours run time, perhaps as much a 4.5.

[Pete7]

Mat, I would agree with you, once you step over 4 or 5 hp then the weight you will be dangling over the stern whilst bobbing about in a seaway becomes a problem, likely to end in tears.

For Mick, how far or fast will you go? well Old Spice a 22ft, 2T rib used to do 2.8 knots with a Seagull Century.

Now the interesting thing about that engine, apart from being the same age as me, is that it was light and had a big diameter prop turning slowly which is exactly what you want at displacement speeds. So give up the expensive 4 stroke and enjoy the smell of 2 stroke in the morning.

Pete

[Matt]

That was the first motor I was allowed to play with as a kid, we had one on the tender for my father's yacht.

He ran it on 10:1 with engine oil, so we didn't get the benefit of the nice smell though.
And I seem to recall the gearboxes were designed to let water in? By design? Holy Smokes (as it did, a lot).

[paintman]

Saving Old Seagulls: Free British Seagull information, Engine serial number identifier,advice, forum and spare parts.

What Oil should be in my gearbox, it looks like coffee coloured sludge?

If your gearbox has a mixture of oil and water in a grey/brown slurry, that’s healthy!

The gearboxes on most seagulls have no proper oil seals, just a rubber grit seal. The oil will leak out and water get in. They are designed to run on an emulsion of oil and water. However, there comes a time when the water content is too high, so if it is inspected every 10 hours use and found watery, replace it with 140 grade oil. It’s a lot cheaper than replacing the gears.

[rik_elliott]

It's a bit against the accepted wisdom on here, but you can get away with smaller aux engines than you might think. I was on a 5.5m when the main motor decided to make extremely upsetting noises and exciting coloured smoke while we were near bramble bank in the solent while the spring tide was running at a fair clip. We only had a 2.5hp 4s mariner as a reserve motor and I was looking at the poor little thing without any real hope it would move us against the tide, but given our proximity to major shipping lanes and a sandbank we needed some maneuverability so gave it a go. Yes it was slow, but against a hard tide we managed just over a knot which actually got us in to hamble and on to the mooring.

Now, we had an anchor, vhf, flairs and sea start membership so had alternatives, but the motor saved us from a potentially dodgy first few minutes and once we were safe we decided to see if it could get us home, which it did.

I guess it all depends on what you need, but I would absolutely feel safer with ANY aux than no aux at all. I think it says it all that I bought the same engine for our little sib and to use as a reserve on our own rib after this experience. I wouldn't for a moment expect to get me home from the nab tower or whatever, but out of the way of shipping or into shelter in a bay where i can drop anchor? Yes please.

[Matt]

Yes, this is my view with my 5. Bembridge is nice anyway and they make good bacon rolls in the duver marina.

[Matt]

Also, seastart. Are many people here members? Are they good?

[FoxZulu]

Originally Posted by Matt

Also, seastart. Are many people here members? Are they good?

We've been members for 3 or 4 years now. Can't say how good they are as we've never had to use them, but we often see them going out from the Hamble.

[Matt]

Ta. Obviously wouldn't want them as a primary line of support (as maybe some people do - it'll be alright mate, we're with sea start etc) - but I always figure it's good to have another "tier" once you've run out of self service options but would prefer not to be calling coastguard/hamble rescue/rnli etc.

[rik_elliott]

Originally Posted by Matt

Also, seastart. Are many people here members? Are they good?

I never used them, but my father in law did when his fishing boat broke down. They came out straight away and towed him back to the Itchen when they realised it was his CDi unit that had popped and not something they could mend while afloat. He was very happy with the service overall.

I think if you only ever go out with other boats they are a bit overkill, but if not then they serve a purpose.