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Old 10 July 2012, 05:08   #1
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Another engine question

Another stupid question ! After kdog's thread re 2 engines, I have another possibly stupid question.

We seldom want to get the RIB on the plane (Searider 4m with flooding hull) but what would be the minimum engine size to achieve this with 2 adults and one dog on board ?

We will mainly be playing in smooth water.

(I shall not show this thread to the dog !)

TIA
P
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Old 10 July 2012, 05:28   #2
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Probably 25Hp minimum for 2 + dog.

Any less and you will struggle with the flooding hull and end up having to literally do a merry dance to get the water out and up on the plane. A fair few sailing clubs used to use SR4/25Hp combos, although many have now upped to 30 & 40.

A 25 will get you about 18-20 knots flat out.
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Old 10 July 2012, 09:31   #3
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Thanks for the reply ... and ...

Ooh dear this is getting tricky. HWMBO wants to be able to plane but I am concerned about weight. There are 2 issues - one - tilting it when we leave it could be overcome by power tilt - two - getting it onto the RIB in the first place is one I'm worried about (yup - we're getting old !)

Our experience to date goes no further than 15hp 4-stroke at about 50kg.

Other options appear to be :

* a Yamaha 30 with e/start, l/shaft with power tilt but webbing about puts this at around twice the weight of the 15

* a Tohatsu 20 which the dealer (v reputable) says would be enough to get it onto the plane - weight seems to be the same as the Toh 15 - but it's more expensive than any of the others, and more still if we want tilt

Ooh dear ooh dear ...

Any/all advice welcome
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Old 10 July 2012, 09:44   #4
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I'm slightly confused; are you planning to remove it from the boat on a regular basis?

I had one with a Yam 25 4-stroke. It would just about plane with 4 people in it.
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Old 10 July 2012, 12:17   #5
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Hi Tim

Tks for that. No - not removing it often but still got to get it on the RIB in the 1st place.

More worrying about double the weight is that the RIB already rides well down at the stern with the current OB - even had a small wash over the transom just sitting tied up in her berth. So what might it be like with twice the weight ?

Have read on here that you can put a 50hp on the 4m Searider but is that when you're trailing not leaving it afloat ?

Any idea what the max advisable weight on the stern might be ?
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Old 10 July 2012, 13:59   #6
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we have an SR4 (with a humber console in it which is quite chunky) that ran a 25 mariner 4 stroke with PTT for a few years that would plane easily enough with two people aboard,it now has a honda 30 with PTT and is fine three up as long as you get the weight forward to get it on the plane (flooding hull is active, ie unblocked)
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Old 11 July 2012, 03:38   #7
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Pragmatist, you have just found a prime example of how one "lump" can be tuned to two horsepowers.

How often are you planning on removing it? A couple of judicious mods to a sack barrow, and you can "lift" the engine off by jacking the box up using the jockey wheel straight onto the sack barrow...
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