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Old 22-06-2014, 18:01   #1
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how much HP for a 35 foot cat?

I have a Prout Snowgoose 35. It currently has a pair of 24 HP Yamaha 4 strokes. Issues the shafts are only 20 inch and cavatate a lot. ALso, they add a lot of extra weight. Originally it had a little 18 HP diedel and a Silette sail leg.
I am thinking of moving to either a pair of Honda 15s or 10s. @% inch shaft electric tilt....etc. They reduce the backloaded weight nearly a hundred pounds each.
So if someone has horrible tales of Honda debacle I need to hear them. But only if you have a proven replacement.

Also how much HP does she need. One of the 25s at 3800 I am told outputs about 18 HP. SO about what two 10s would do. I have never had both Yams running at the same time....another reason I am looking at Honda.....so it seems that the twin tens would be enough. I can go the 15s. The weight difference is that much, I get double the amp output and an extra 10 HP.

All thoughts appreciated.
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Old 23-06-2014, 16:26   #2
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Re: how much HP for a 35 foot cat?

If you go with the 15hp, then why not the 20? They are the same weight, but you get 5hp more.

Did you consider the Suzuki 15/20hp? They would save you a few pounds over the Hondas, but I don't know if they come in the extra long shaft model that the Honda does.

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Old 23-06-2014, 16:44   #3
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Re: how much HP for a 35 foot cat?

Quote:
Originally Posted by colemj View Post
If you go with the 15hp, then why not the 20? They are the same weight, but you get 5hp more.

Did you consider the Suzuki 15/20hp? They would save you a few pounds over the Hondas, but I don't know if they come in the extra long shaft model that the Honda does.

Mark
In the US only the Honda 15 comes in the extra long shaft not the 20. Seems in Australia they both come in the extra long shaft.
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Old 23-06-2014, 16:47   #4
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Re: how much HP for a 35 foot cat?

I have Honda 20's with the 28 inch shaft on a 44 foot around 6 tonne boat. They're plenty of power, cavitation isn't a problem, they work very well.

However I recently installed a pair of Tohatsu 20's to a similar boat. They are available with a 25 inch shaft - a 5 inch factory made extension is fitted by the retailer - and because of their more compact bracket, their actual propeller immersion depth works out to be pretty much the same as the Honda's.

There are some photo's of the installation here: Recovering From TC Oswald.

All the specs, for power, weight, gear ratios and props are very similar to the Honda's, but the Tohatsu are a fair bit cheaper. IMO easier to service too, as oil filters etc are more accessible.

I'm very happy with my Hondas, but if I was repowering I'd almost certainly go with the Tohatsu 20's now.
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Old 23-06-2014, 16:47   #5
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Re: how much HP for a 35 foot cat?

There are some Yamaha and maybe Suzukis that are special built /xtra long shaft/ high thrust/large prop types in the 8-10hp range. Trolling motors. Those would be perfect. By the time you buy two of those those with power tilt etc.... well It aint gonna be cheap!
You can see how long the shaft is and the big prop on the Yamaha here. I would imagine Merc, Suzuki, Honda etc are similar but don't know....
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Old 23-06-2014, 17:12   #6
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Re: how much HP for a 35 foot cat?

Actually the new Yamaha 9.9 HT's are amazingly cheap (in Aus at least) right now. A friend just bought a pair, and they cost about the same for two as one Honda 20 cost me five years ago. (he paid $3060 Aus each)

However, the power tilt isn't available in combination with the long shaft on the Yamaha 9.9. If you can access them to manually tilt them, they could be a good option too.
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Old 24-06-2014, 06:55   #7
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Re: how much HP for a 35 foot cat?

Great feedback!
Checking the pricing on the Tohatsu, so far looks similar to the Honda. Trying to find a dealer who can do the 5 " extension. So far no joy.

Suzuki does not come in an Xlong just a 20 above 9.9HP
Tohatsu cannot get the 5" extender in the US

Mercury does not have the 25"
Looks like process of elimination is back to the Hondas.
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Old 24-06-2014, 07:16   #8
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Re: how much HP for a 35 foot cat?

We have a single 25hp merc (4 stroke, fuel injected) on our Gemini and it seems to be about perfect. It does steer with the rudders so it's far better than a fixed prop but obviously not quite as good as twin engines.

If conditions are calm, you don't need that much power (10-15hp would be fine) but fighting a strong head wind or waves the extra HP is needed if you want to continue to make head way.

I would think a pair of 10-15hp outboards would give you similar thrust.

Ours is only 20" but the bucket that its on is adjustable so it works well (closing in a 1000hrs and it's cavitated twice for a couple seconds each time). We did check when purchasing and there was an after market extension kit (Bay Manufacturing, I believe).

This was back in 2007 but $5k installed for a brand new drivetrain (not just motor) is hard to beat.
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Old 24-06-2014, 08:09   #9
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Re: how much HP for a 35 foot cat?

We have been pushing the Prout with a single 25 and in a nasty head wind and choppy seas it pushed the boat ok. It was cavitating constantly and that probably cost us a bit of speed. We have a set transom and no other adjustment. Merc dealers here won't do the kit so adding voids warranty. Traps everywhere. I am leaning to the 15s but am wondering if the 10s with no cavitation operating and normal throttle wouldn't be similar to what we had in the storm with the single 25.
Tough choice between enough and overkill. especially with the price difference.
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