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Old 13 March 2006, 18:03   #11
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I suspect 19" will be about right.

Using 5500rpm, gear ratio of 1.8, slip of 18% and 19" pitch you'll be doing 39knts.

On my 6.5mt with the 200 Suzi it pulled about 46-47kts.

So that calculation is going to be pretty close on your 8.8mtr unless it's very light. 24" will be way to high.
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Old 13 March 2006, 21:46   #12
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I know but it was a good price!!!
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Old 14 March 2006, 04:25   #13
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I am sure the 24 will be too big for that boat - the 19 will be fine to start with - maybe lightly loaded it would be ok with a 21, the type of prop also plays a big part as does the balance of the boat fore and aft. If you ask me I wouldn't buy any more stuff untill you've run it in and know wether you're getting anywhere near the rev limit or not.

If you go back to when you asked advice about the lifter I told you at the time not to get one, but Stainless Marine were the best - Regardless of that I have another little nugget for you - get a water pressure guage and watch it like a hawk or you WILL blow the engine up! Lifting the engine once you get going has 2 effects - it reduces drag on the gearbox which allows higher speeds, for instance at 65 mph you would expect 3-5 mph gain, and it also reduces bow lift as the engine gets higher.

The other thing that lifters and set back brackets do is put more stress on the transom (think of the leverage effect).
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When a boat looks that good who needs tubes!!!
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Old 14 March 2006, 04:26   #14
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Quote:
Originally Posted by codprawn
I know but it was a good price!!!
That's why it was a good price

Aren't the builders (or engine suppliers) going to trial the boat with various props?

Depsol said 41 knots exactly - does he know something we don't - being in the CIs?
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Old 14 March 2006, 09:39   #15
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Quote:
Originally Posted by Cookee
I am sure the 24 will be too big for that boat - the 19 will be fine to start with - maybe lightly loaded it would be ok with a 21, the type of prop also plays a big part as does the balance of the boat fore and aft. If you ask me I wouldn't buy any more stuff untill you've run it in and know wether you're getting anywhere near the rev limit or not.

If you go back to when you asked advice about the lifter I told you at the time not to get one, but Stainless Marine were the best - Regardless of that I have another little nugget for you - get a water pressure guage and watch it like a hawk or you WILL blow the engine up! Lifting the engine once you get going has 2 effects - it reduces drag on the gearbox which allows higher speeds, for instance at 65 mph you would expect 3-5 mph gain, and it also reduces bow lift as the engine gets higher.

The other thing that lifters and set back brackets do is put more stress on the transom (think of the leverage effect).

The MAIN reason I got a transom jack was to give me extra space in the boat - it has 10" of setback. The idea was to have a rear bench seat but that's another story......

Yes I have asked for a water pressure guage to be fitted which I will watch like a hawk - if it proves to be a prob will fit a low water pickup.

I know about the extra stess involved - which is why when I get the boat I will replace the washers with some hefty pieces of angle.
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Old 14 March 2006, 09:49   #16
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Quote:
Originally Posted by Searider
That's why it was a good price

Aren't the builders (or engine suppliers) going to trial the boat with various props?

Depsol said 41 knots exactly - does he know something we don't - being in the CIs?

Not the case - bloke had been using it on a 19' light boat so he never had probs.

Doubt it - I specced the 19" to be supplied for full load use - as Cookee says a 21" will be the other option but I thought I may as well try the 24" to see what happens.

As to what Depsol says I was wondering the same myself - they are supposed to inform me when they are doing the sea trials - they haven't mentioned anything!!!
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Old 14 March 2006, 10:51   #17
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Quote:
Originally Posted by codprawn
I thought 24" was a finer pitch than 19" or - have I got it the wrong way around?


with the size and beam of your boat do you have any idea of prop slip expected and what you think the max speed will be for your boat?

Not sure you will be able to pull a 24'' prop but it is trial and error.
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Old 14 March 2006, 11:13   #18
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Originally Posted by codprawn
Not the case - bloke had been using it on a 19' light boat so he never had probs........
I thought it was new "old stock" engine?
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Old 14 March 2006, 11:21   #19
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this is getting interesting


seems some elements of the story are starting to unravel .................
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Old 14 March 2006, 11:23   #20
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I thought it was new "old stock" engine?
silly billy......

its a second hand new "old stock" new model from the 90's
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