Never content.. more tweaks.. Prop size and drips

oGaryo

oGaryo

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Ran the boat at WOT momentarily yesterday but pulled back almost immediately as the revs shot up to 5200 rpm at about 30Knts with more to go on the remote.... I think the rev limiter kicked in. Prop currently fitted is a 16 x 16 Black Max so I recon I need to go up a pitch and try again, possibly 2 i.e. a 17 or 18 with 15in diameter.

What's holding me back making the purchase is I can't work out the gear ratio of the sterndrive as it's been painted quite heavily masking the numbers.. I do have the serial number so will that give me a clue or is there anywhere else I can check to get the gear ratio to punch in to the Mercury Prop Selector tool?

Engine fitted is a 5.0l MPI.

Hope you can help, thanks Gary

p.s. I was cruising at 24knts doing 4500 RPM

p.p.s. had some salt water in the bilge on return so need to check that out too.. not alot, about a litre
 
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If you are desperate to know, you can take the drive off and there should be a letter stamped on the splined shaft - this corresponds to the drive ratio.

Or, just experiment with the prop finder to work out what the ratio currently is.
 
OK, this is all speculation ! We have similar boats with the same engine, I can't remember the drive ratio in my leg, but I have had chance to play around with props.

Tried 3 standard Mercruiser props (15, 17 and 19 pitch), the 15 spun like a blender took off like a scalded cat to about 10kts, but then started to get huge prop slip or cavitation. 17" worked well across the rev range, 19" was much more relaxed but I didnt think it would get me on the plane when fully loaded.

Tried an aluminium 4 blade 20" but didnt work well, need a lot less pitch. Best of the bunch was a 5 blade stainless High Five 17", but didnt get chance to do a full speed run because I was on Windermere at the time and I never break the speed limit ;)

After all the playing and testing I thought the standard 3 blade 17" quicksilver prop was the best all rounder when you include purchase price in the mix.
 
rafiki_ said:
Sorry, can't help with the prop, but could the bilge water just be finding its way in through spray?
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possibly but I don't think we had much this weekend, even on the Saturday.... the only thing I would suspect is I've been told the Rinker 250's suffer from water ingress through the engine hatch hinges in heavy following seas and low speed but again, it wasn't that bad for the waves to come up over the swim platform.
 
landlockedpirate said:
OK, this is all speculation ! We have similar boats with the same engine, I can't remember the drive ratio in my leg, but I have had chance to play around with props.

Tried 3 standard Mercruiser props (15, 17 and 19 pitch), the 15 spun like a blender took off like a scalded cat to about 10kts, but then started to get huge prop slip or cavitation. 17" worked well across the rev range, 19" was much more relaxed but I didnt think it would get me on the plane when fully loaded.

Tried an aluminium 4 blade 20" but didnt work well, need a lot less pitch. Best of the bunch was a 5 blade stainless High Five 17", but didnt get chance to do a full speed run because I was on Windermere at the time and I never break the speed limit ;)

After all the playing and testing I thought the standard 3 blade 17" quicksilver prop was the best all rounder when you include purchase price in the mix.
Click to expand...

Excellent, thanks.. sounds likeI need to start with the 17
 
oGaryo said:
possibly but I don't think we had much this weekend, even on the Saturday.... the only thing I would suspect is I've been told the Rinker 250's suffer from water ingress through the engine hatch hinges in heavy following seas and low speed but again, it wasn't that bad for the waves to come up over the swim platform.
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What about the engine air intakes on the side of the hull? I'm not sure if you can see these from the cockpit when blasting underway.
 
rafiki_ said:
What about the engine air intakes on the side of the hull? I'm not sure if you can see these from the cockpit when blasting underway.
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quite possibly mate... I'm thinking of dusting a few susepct areas with talc next time I'm out... could even be something as simple as a leaky pipe on the heads.. a portlight looks a little susepct too in terms of sealing
 
oGaryo said:
like it:) let's put it out there and see what comes back.. anyone got a bunch of props I can play with?:)
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just think gary, you,ll do more miles up n down the slipway than on the water !!!!!! teehee teehee.......still your launch n recovery techniqe will be like a mclaren pitstop !!!!...i,ll drive the stopwatch !!!!!..........(sorry)...............yes im off now...............
 
Not wishing to be a doom monger, but is the engine raw water cooled? If so, look for a leaking water pump - there's a small hole under the pump from memory and if the shaft seal's shot it will leak seawater into the bilge when the engine's running.
 
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