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Old 08 November 2007, 09:56   #1
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New toy / Prop pitch

Finally picked up the new toy - A Delta "Seasafe" (a.k.a the Grandad of the Humber Ocean Pro - I seem to attract "classic" boats!) Whilst looking over the engine last night I discovered it has a 12" pitch prop, which did seem a little fine, considering my old SR with a 25 was running a 13" and I can't find any mention of anything so fine on any threads.... Knowing the boat's history, I reckon it spent a fair bit of it's time loaded, which may explain it. The previous owner told me he clocked 20 knots on a handheld GPS last year.

So here's the Q for all you O-Pro owners (ideally those with an engine arond the 50/60 Horse mark) - What pitch are you running, and does 20knts sound slow for this setup?
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Old 08 November 2007, 11:18   #2
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Well, FWIW, my buddy runs a Zodiac Pro 16 with a Merc 4-stroke 60hp, and uses a 4-blade 12 inch SS prop. You wouldn't be alone.

How's your WOT rpm? If you're not nailing the rev limiter, you're probably pretty close.

On my boat, the difference between solo and fairly heavily loaded is nearly a thousand rpm, so load could account for the small pitch number. Better to check it out experimentally, though, rather than guess (cheaper, too.)

jky
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Old 08 November 2007, 20:31   #3
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avon seasport 4.25

avon seasport 4.25 yammy 60hp 2stroke,,40mph at 5500rpm,3blade,19x14 s/s solas prop seems to run same speed loaded or not once trimmed out
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Old 09 November 2007, 04:15   #4
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Quote:
Originally Posted by 9D280 View Post
Finally picked up the new toy - A Delta "Seasafe" (a.k.a the Grandad of the Humber Ocean Pro - I seem to attract "classic" boats!) Whilst looking over the engine last night I discovered it has a 12" pitch prop, which did seem a little fine, considering my old SR with a 25 was running a 13" and I can't find any mention of anything so fine on any threads.... Knowing the boat's history, I reckon it spent a fair bit of it's time loaded, which may explain it. The previous owner told me he clocked 20 knots on a handheld GPS last year.

So here's the Q for all you O-Pro owners (ideally those with an engine arond the 50/60 Horse mark) - What pitch are you running, and does 20knts sound slow for this setup?
I can't be certain but you might be looking at the diameter not the pitch? What engine does it have?
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When a boat looks that good who needs tubes!!!
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Old 09 November 2007, 04:38   #5
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Jyaski,
WOT RPM? The tacho is on my shopping list.......

Cookee,
It's a yam 55 2cly 2stroke C.1982 vintage. I don't think so, unless it's 10 5/8" pitch?



I won't be able to get it out for a couple of weeks, but did get a spin in it before I got it. It just seemed a little underrated for what it is. There's a few odds & sods to do before I go trial it properly, like fitting the radio, sort the two "reverse thrust" blades on the prop..... - I suspect straigthening the prop out might help a little , and I have also removed a set of "wings" from the cav. plate.

There may be nothing wrong with it, but It just seemed from the vibes I've got from the threads about prop pitch that 12 may be a little low for this combo. It's more a case of idle curiosity at the moment, I may find there's so much reinforcing on the toobs from it;s previous life it needs a 12 to get moving!
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Old 09 November 2007, 11:36   #6
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Jyaski,
WOT RPM? The tacho is on my shopping list.......
Yeah; it's about the only way to tell whether the prop is the an acceptable pitch/diameter or not. Load the boat "normally", find flat water, firewall the throttle, trim up to max rpm and see what you get. Should end up in the upper part of the manufacturers max rpm range.

Without a tach, it's kind of guesswork. I suppose you could use an automotive clip-on type tune-up meter, if you are still waiting for gauges.


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There may be nothing wrong with it, but It just seemed from the vibes I've got from the threads about prop pitch that 12 may be a little low for this combo. It's more a case of idle curiosity at the moment, I may find there's so much reinforcing on the toobs from it;s previous life it needs a 12 to get moving!
If it was a work boat, it may well be set up for heavy loads. I run a 15" prop normally, but have a 13" for times when I need to carry a *lot* of divers and gear.

jky
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