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Old 22 October 2004, 11:08   #21
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Bilge Rat
I get 30 Knots on my 4 Metre Sea Rider with an Merc 50 and a 12" prop. Thats according to the GPS. Dunno about Revs. I just got the Rev Counter fixed last week and have yet to try it out. I also have a 13 " prop which hasn't been put on yet.

I went from a 11" to 13" on my last boat and that killed the acceleration and it was quite an easy planing boat. It was a real struggle in rough seas to get the boat to do anything.

I have a feeling that the Sea Rider will be even worse if its over propped. Having read your experiences though I think I will give it a try soon.
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Old 22 October 2004, 17:51   #22
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Biggles......Not sure i'd call myself experienced at all, i only had one sized prop on my last engine and was told by steel developments that the engine was slightly over proped for its size, but the boat performed well so i wasn't that worried.
When i changed engines the new one came with a 13" pitch prop, i thought it wouldn't perform very well considering i'd had a 19" pitch prop on a smaller engine but to my ammazement it does and actually performed a lot better than i had thought it would.

Ok so now the science bit, we are told that if you increase the pitch your'll loose top end revs but gain a higher top end speed, the downside of course is the lose of hole shot or if the boats loaded it will struggle to get on the plane, for this reason ski boats generally have smaller pitched props, for them top end isn't so important but getting the skiier out of the hole is.
Remember that your gear ration will also effect the performace, a high thrust gear box is designed to give maximum power through out the entire rev range, but because the of the specific gear ratios your'll lose slight performance at the top end.
If i had a big bag of money it would be good to try each different sized prop under the same exact conditions and loadings and see what actual difference each made to top end speed and the revs. Its also important that the engine runs within its specified rev range, over reving will cause excessive vibration and could damage the engine, if on the other hand the engine is running a lot under the specified rev range it will cause the engine to labour excessivley and may cause damage also.

if you have the prop then why not give it a go and see what difference it actually makes, set up some same criteria to test it under and repeat the same test with the different size prop, it may be a case of having both sizes and changing them over for specific days out, if the smaller pitch performs better with three big guys on rather than the bigger pitch then why not take advantage of having the choice.
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Old 26 October 2004, 08:14   #23
CND
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The whole prop issue has mystified me for a number of years! After having been involved with putting props on a number of different boats, both singles and twins there seems to be the hard and fast rules, as outlined abouve, but no substitute for just simply trying different pitches and blade configurations that simply seemingly suits the boat best, the hicher speed handling seemingly being decisive.

I am aware that even the Class1 powerboats regularly send their props back to some stupendous milling operation to have millionths of an inch shaved off here and there...

Can anybody reccomend any resources/books on props that provides a boring comprehensve read on the subject of fast boat props?
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Old 23 December 2005, 06:39   #24
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Quote:
Originally Posted by Robert1
If theres a drawbar sticking out of a hole in a garage door, surely its pretty obvious theres something going on?
If they have wheely bins in your Area then buy one and cut a hole in it to cover the protuberance! If you don't have Wheely Bins (well somebody has got to live in Wolverhampton I guess) use a Dustbin..

You can also buy a little electric pump for about 30 quid which will inflate it in about 2 min's
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Old 23 December 2005, 14:38   #25
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My 5.4 Searider is a bit more than 5.4 arse to nose- its nearer 6m plus the drawbar. I ended up renting a lockup for *cough70cough* quid PM. But its in the dry and under lock and key. I have to deflate the port tube just enough to allow the sponson to fold in 1". Takes longer to get the pump out than it does to blow it up.

Bilge Rat:
Just finished servicing the engine and hope to try it out next week if your about. Found that high rpm timing was a long way out, so should now pull more than 5000 RPM WOT With a 19" prop.

Interesting you get about 2NM/L as I thought your yammie ran on water and never needed filling up.

Tim'mers.
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Old 24 December 2005, 10:28   #26
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Surely the motor on a 5.4 sticks out almost as much as the rear of the tubes so deflating wouldn't gain much?

I'm moving in a month and my sr4 will get a nice new home in a huge carport that's going on the side of the bloody great garage and workshop that's already there. Might have to upgrade-could do with a 5.4 or 6m and a 4-stroke (when I win the lottery.... ) the garage is 10m long and the carport will be the same size.


why did this thread reappear after a year?
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Old 24 December 2005, 13:02   #27
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Quote:
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) the garage is 10m long and the carport will be the same size.


why did this thread reappear after a year?
Stop showing off.

and in answer to your q1uestion you can't have too mny threads abou Seariders!
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Old 24 December 2005, 14:13   #28
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I have a 5.2 m hardnosed osprey in a standard garage but had to cut a hole in the door for the towhitch. The up and over door also hit the bow of the boat when opening so I had to take off the mechanism and hinge the door at the top. Its a bit of a pain as the door has to be proped up every time. I have a vacuum cleaner permenantly mounted on the wall and use a long tube on its exhaust to reinflate the tubes, it only takes a few seconds. Had to make a hinged bracket on top of the frame to take lights and ariel.
Well worth the effort to keep the boat safe.
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Old 24 December 2005, 18:43   #29
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Quote:
Originally Posted by Rogue Wave
Stop showing off.

and in answer to your q1uestion you can't have too mny threads abou Seariders!
What, the world doesn't revolve around seariders?


Not showing off anyway-the garage and carport are almost as big as the ground floor of the house...
Just the way it should be


Merry Xmas!
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