Outboard size / which engine

Discussions related to outboard engines
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Danwash
Under way
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Joined: Wed Oct 14, 2009 8:04 pm
Location: Jersey

Outboard size / which engine

Post by Danwash » Tue Mar 30, 2010 6:08 pm

Right Moonshadow came with a rattly old mariner 4 of unknown age and basically I hate it. It sounds like a tin of particularly angry wasps, and moves the boat at about 3 knots. SO I'm thinking short shaft mercury 5hp which I can get at a knock down price. I will have a charging rectifier fitted and stick a gas can under the starboard locker.

Down to the gritty nitty,

1.Where should the cavitation plate end up wrt the hull? ( I plan to shift the transom board up / down to achieve perfection)
2. do you reckon I could fit a transom mounted transducer / paddlewheel for a sounder / log in the well as well?

Nice to see the forum being used again, my boat is super, I love her, she is great. Photos of exploits to follow!

Dan
Dan

Terry
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Joined: Thu May 18, 2006 8:56 am
Location: Gwynedd, North Wales

Post by Terry » Tue Mar 30, 2010 11:18 pm

Hi Dan
Mariner /Mercury / Tohatsu 4,5 & 6hp – their all the same outboard with different carburation the only difference for you is that they now all have to be 4 strokes. The 4 stroke has the same length shaft as your mariner 4 but the engine its self is taller (original short shaft is now no longer produced. What was the standard length is now call a short shaft). Where the cavitation plate is positioned will be dictated by getting it as high as possible whilst clearing the outboard cover and/or tiller. I upgraded from a mariner 4 to a tohatsu 5 sail drive and to get the plate just projecting below the hull I had to raise the cover as high as the transom would allow. The alternative is not to bother with the cover but you will still be limited by the tiller.
I was tempted by a Honda but I believe this would have involved hacking a hole in the transom and, at the time, I didn't fancy that, however, Mike (mikeboatproject) is offering an insert to tidy up the hole.

As for the paddle wheel, I wonder if there might not be too much turbulence in the well?

robvega
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Posts: 97
Joined: Wed Nov 22, 2006 5:37 pm
Location: Cleckheaton, West Yorks
Boat Name: Vega
Sail Number: 191

Post by robvega » Wed Mar 31, 2010 12:41 pm

Dan
I have my log/depth transducer on the back of the skeg on Vega. It seems to work ok close to the prop like that, I get similar readings under sail or power. I agree with Terry, I don't think it would work in the well itself. Of course there are no holes through the hull for it as the cable is led up through the well & into one of the lockers.
Rob

Terry
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Joined: Thu May 18, 2006 8:56 am
Location: Gwynedd, North Wales

Post by Terry » Wed Mar 31, 2010 2:15 pm

Dan,
My hull is, as most, single skinned in the locker under the sink and both transducer and impeller are mounted here. Their position is critical though because they need to be as close to the centre of the boat as possible. The only problem with this is that the paddle can now be damaged by the trailer rollers. You just need to remember to pull it up its tube a bit when getting the boat out. The advantage of mounting the paddle here is it’s well out of the way of things but, most importantly, you can pull the wheel out for cleaning and all the water stays in the locker. It doesn’t take much to pump it out (about a bucket full)
One of the swift series (can’t remember but it might be 400’s) is double skinned under the sink so, if the locker has a smooth interior, put them somewhere else!

Danwash
Under way
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Joined: Wed Oct 14, 2009 8:04 pm
Location: Jersey

Post by Danwash » Wed Mar 31, 2010 5:41 pm

I hear what you're saying, we used to have a transom mount transducer on a dory we owned, with a 30hp. I figure if it'll cope with planing and all the inherent wash and turbulence from that, it'll cope with anything that happens in the well. I like the no holes approach. but will give it a go with mates gear before buying.

Now will somebody spell out (pretend I'm stupid) exactly which motor I need, and how to get the darn thing to fit!? I really don't want to buy £600 of motor and be stuck with something I don't like.

Ta Dan
Dan

Terry
Cruising
Posts: 229
Joined: Thu May 18, 2006 8:56 am
Location: Gwynedd, North Wales

Post by Terry » Wed Mar 31, 2010 6:44 pm

Don't know if anything just slots in. You've probably done this already but can I suggest you check out "which Engine" in the outboard section.
Danwash wrote:I hear what you're saying, we used to have a transom mount transducer on a dory we owned, with a 30hp. I figure if it'll cope with planing and all the inherent wash and turbulence from that, it'll cope with anything that happens in the well. I like the no holes approach. but will give it a go with mates gear before buying.

Now will somebody spell out (pretend I'm stupid) exactly which motor I need, and how to get the darn thing to fit!? I really don't want to buy £600 of motor and be stuck with something I don't like.

Ta Dan

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