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Old 17 October 2014, 02:31   #1
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Engine for 5.4 searider

From what I've read, the conventional 90hp yamaha seems to be a popular engine for the Searider 5.4.
If I was going to buy a new engine, would this still be the best choice or are the four strokes going to be much more fuel efficient (although heavier)?
I'd be interested in any opinions.
Cheers
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Old 17 October 2014, 03:27   #2
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hi mate

i had a brand new 60 yam on my fast fisher brilliant engine,
i now have a 90 Suzuki on my rib again brilliant engine,
but would choose the Suzuki over the yam because the yam has a timing belt the Suzuki has a chain in an oil bath personnel preference only.

regards jeff
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Old 17 October 2014, 04:48   #3
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Cheers for the reply Jeff
I guess yours are both 4 stroke?
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Old 17 October 2014, 05:01   #4
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The new Yam F70 weighs 117kg however the F75 & F90 weigh 166kg

That's a lot more weight for only 15-20hp more power.

I'm not sure how well it would go with a 70 but you may find the 90 will be a bit on the heavy side?

Hope that helps
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Old 17 October 2014, 07:48   #5
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Quote:
The new Yam F70 weighs 117kg however the F75 & F90 weigh 166kg
Mercury's 75hp and 90hp four-strokes are 163kg; Evinrude's 75hp and 90hp E-Tecs are 145kg; Suzuki's 70hp and 90hp engines are 155kg.

Yamaha seem to have done really well on the weight of the F70. That's only 7kg more than a 25hp we used to have!
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Old 17 October 2014, 07:54   #6
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your right both engines four stroke my 90 is on a 6m rib i usually carry loads of kit and 140 ltrs of fuel and still get 35-45 mph out of her at WOT she will plane at 20 mph in most sea conditions [that you are able to plain]that amount of fuel gives me around 160 mile range my engine is a 2009 the new ones are lean burn good bit better on fuel.

regards jeff
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Old 17 October 2014, 08:17   #7
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The 5.4m Searider is a strange one. Most manufacturers reduced the horsepower ratings on their transforms to reflect the weight of the four stroke engines. The thinking became more about how much weight was on the back rather than the Horsepower. A Rib that would take a 70 was reduced to 60 and so on. It may be an idea to find out what is recommended for the avon currently for insurance porpoises. My choice would always be a 90 Yam used followed by the equivalent weight Etec if I was going for new. Four Strokes are fine for heavy hours if you are going to do anything like 700 - 1000 hours per year. If not, why deny yourself the power to weight ratio (and ease of maintenance) of the two stroke. There are quite a few on here that can give accurate fuel comparisons between similar two and four strokes.
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Old 17 October 2014, 08:46   #8
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As said the 90 two stroke yam is by far the best choice. Ive got a 4.7 mod SR and taken the plunge on a new F70 as the weights is 12 kgs under the transom weight and rated to 70 also so hoping this will give me 40 kts. The SR 54 really needs a 90 and weighing in at no more than 140 kgs to give a good balanced ride
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Old 17 October 2014, 09:20   #9
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The Zodiac Mil-Pro website is currently recommending 80hp for an SR5.4, but it doesn't look like a maximum, just a recommendation.

As far as I know, only Suzuki and Honda make a 80hp motors, and they're both about the same weight as their 90s. The other manufacturers seem to prefer 75hp, and they all seem to be the same weight as their 90s as well.

As far as power–weight goes:

Yamaha 90AETOL 2-stroke: 90 120 = 0.75 hp/kg

Yamaha F70: 70 117 = 0.60 hp/kg
Yamaha F90: 90 166 = 0.54 hp/kg

E-Tec 60: 60 109 = 0.55 hp/kg (the nearest to the Yamaha two-stroke for weight)
E-Tec 90: 90 145 = 0.62 hp/kg

So the 60hp E-Tec isn't really all that good for power/weight, but the 90 is the nearest thing to the Yamaha 2-stroke (25kg weight penalty), which you can't get new for leisure use nowadays anyway.

So if 90hp is an absolute 'must', the E-Tec 90 has it, but if the extra 25kg is too much, Whisper's suggestion of the F70 looks better.

Not that power and weight are everything, of course .
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Old 17 October 2014, 09:53   #10
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Thanks for all the advice.
So from what I understand, it sounds like the 2-stroke 90 Yam is the one to go for - due to the much lower weight. As I won't be doing large numbers of hours, it doesn’t sound like the increased fuel efficiency of a 4-stroke will also be too much of a factor - this will also be partially offset by the reduced cost of a 2 stroke. Luckily the RCD does not apply here (Channel Islands) so we can still legally buy 2-strokes.
Thanks
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