Outboard for Vivacity 650

[chrishewett]

I am looking for a used outboard for my Vivacity 650. I borrowed a 6hp longshaft Mariner and was dissapointed to see that it only pushed me along at barely 4knots. What hp should I be looking for so that I can make headway against a 4knot tide.

The other question is how much swamping can a modern outboard take before it cuts out. A few months ago I found myself to close to the beach when an onshore wind blew up and I needed the motor to make some searoom. As the sea got up at the same time I had some scary moments as the motor was almost dissapearing under water as the boat pitched. Luckily it didnt falter and I was soon out of danger but it made me think.
Any input would be appreciated.
Chris

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[Guest]

Difference between types

There are different form sof Outboard and each designed for a particular job.

The average outboard is designed for revs rather than thrust and drive along the average dinghy / tender fine. Go up in size and they are more geared for the runabouts and speedboats.

When it comes to sail-yachts and powering them .... it is better to look at the Sailpower / Saildrive type ..... eg. The Mercury 7.5hp Saildrive is a heavy engine, but the thrust is far greater than comparison with average 9hp ..... The way they do it - they are geared down more and propellor is more matched to a sail-boats needs ..... the gearbox is the bit that makes these engines a bit heavier ....

I had a Merc 7.5hp Saildrive on my Snapdragon 23 and it was fine ..... it would get me in / out of Langstone at most states of tide except full bore in centre of race ..... Funny thing is a pal of mine had a Merc 9hp on his Snap 21 and my 23 with the 7.5hp regularly overhauled him !!!!!!

Yes they cost more and many will let you know that they have exsited on standard outboards on their boats. Fine - I don't argue ...... but once you experience the difference of an outboard designed for sail-boats - then you'll see the difference.

An advantage also is that they will run at lower throttle for same result as a standard engine ..... so being a bit more economical ....


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[Colin24]

Re: Difference between types

That is something I’ve not been aware of but sounds like something I need to know.
What should one look for in the spec of an outboard that will indicate it’s thrust or indicate that it is of the type you mention, i.e. suitable foe sail boats?

Colin


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[Guest]

Re: Difference between types

The Merc's are actually named as Saildrives on the casing.

The book also gives digram of one type against another ...

But basically the Outboard Dealer should be able to point in right direction.

I may be wrong - but I am not sure EVERY manufacturer makes the different types.

Mercury make it in 7.5hp and 9hp ..... well they did, probably have slightly diff. sizes now ....



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[VicS]

I would have thought that 6hp would have been sufficient but you would not want less.

The difference between a standard outboard, aimed at fast run abouts, and an otherwise identical model intended for a sailing boat is the propeller. For the slow displacement hull you should have a prop with a larger diameter but a smaller pitch.

For example my 6hp Evinrude Yachtwin has a 23.5 x 16.5 cm prop but the standard 6 has a 21.6 x 22.9 cm prop. That's a big difference in pitch.

Your dealer should be able to advise you on the propellor options available and help you select the most suitable.

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[chrishewett]

Interesting. I have obviously got a lot to learn!
Could it be that a different prop on the inboard would help. At the moment it has a three bladed prop of a diameter of about 23cm. How do you tell the pitch? Measuring roughly the depth is about 4.5cm. Using this I cannot go any slower than about 1.9 knots at tickover but at full revs no more than 3.2knots. The manual says tickover is 800rpm and max revs 1650rpm.
Chris

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