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Old 24 December 2005, 18:47   #1
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Country: UK - Scotland
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High thrust. Good or Bad?

A few questions guys. Ive got a yamaha 50hp 4stroke high thrust fitted to a valiant 490. Is this a good engine for my boat or would I be better with a normal 50hp? Also what top speed do you think I can get? Just fitted the gps but not on the water till march to do a top speed reading. Thanks in advance guys. Jieboy. P.S Merry Christmas to all.
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Old 26 December 2005, 04:21   #2
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Jieboy,
high-trust engine setup is just good for pushing heavy loads i think.(i have see a 50hp Yam 4stroke on a sailing boat)
With such a engine you are unable to get high top-end speeds.It al has to do with the gear ratio in the engines gearbox.
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Old 26 December 2005, 04:38   #3
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You'll be able to change top-end speed by changing prop. The High thrust engines have bigger props than normal so if what I've seen of them is typical you'll get a lot better holeshot than with a normal engine-my sr4 with a standard 50hp got walked over on holeshot by a 17' fishingboat with a 60hp bigfoot mariner as he was getting less slip.
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Old 26 December 2005, 11:01   #4
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High thrust

Hi guys

Did you read the yamaha brochure before you bought ??

I have 6.5m Redbay , 200hp v6, fuel capacity approx 230 litres , plenty of safety gear and i suspect about 3x weight of your valiant . i am considering a 9hp high thrust as an auxillary.

Don't waste your time fitting the engine unless you are thinking of getting a trawler or tug license.

Rgds
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Old 26 December 2005, 11:10   #5
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Quote:
Originally Posted by Jieboy
A few questions guys. Ive got a yamaha 50hp 4stroke high thrust fitted to a valiant 490. Is this a good engine for my boat or would I be better with a normal 50hp? Also what top speed do you think I can get? Just fitted the gps but not on the water till march to do a top speed reading. Thanks in advance guys. Jieboy. P.S Merry Christmas to all.
Contact a prop specialist - someone like steel developments - you should be able to get a good result with a higher pitch prop than normal.
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Old 26 December 2005, 12:10   #6
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With right prop. you should gain similar speed as I got

see here: http://rib.net/forum/showthread.php?t=12484&page=1&pp=4 post#4

Bogi
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Old 26 December 2005, 19:27   #7
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I got a 50 HP Yamaha High thrust on my 4 mtr searider. it does 33 Knots + and fuel consumption is good. Acceleration is out of this world. It came with a 11 inch prop but they gave me a 15 inch prop and that goes well. Probably a 14 inch prop would be best.

Only bad point is it gives off a bit of a rooster tale.

I bought it because it was the right price. I knew what High thrust meant but second hand I just couldn't find a normal 50 HP last summer at anywhere near the right price.

I really don't have a problem with the High thrust and because its pretty new I would be prepared to put it on a 5.4 mtr searider.
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Old 27 December 2005, 08:49   #8
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Biggles, so your saying that you get very good acceration with a good top end aswell? Sounds good to me. Think ive got a 15 prop on mine,might try a 14.
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Old 27 December 2005, 09:19   #9
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Jieboy,

I don't have an issue with the engine. Its been good so far. Ideally I would have got a normal 50 HP but :-

When i wanted one during the summer a) I couldn't find anything half decent and b) this engine came along at a very good price.

Weight has been a bit of an issue with the boat but I've done well over a hundred hours with it in all sea conditions and I haven't sunk yet ! All the 50 HP 4 strokes PTT are probably a bit heavy for the Searider 4M.

Regards Nick R.

Any thing i can help you with info wise please let me know.

I just got mine serviced for Ł80 plus parts and will be getting back out on the water later in January.
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