Reply With QuoteG'day
You could do that......... but on a 25hp, it's practically pointless.
You're best off checking the engine height, and pitch of the prop in relation to what your load is. Also play with the trim.
Dave
I have a new 25hp yamaha on my 3.85 Quintrex and am thinking of changing to a stainless steel prop for a bit more top speed. Is this the right thing to do?
G'day
You could do that......... but on a 25hp, it's practically pointless.
You're best off checking the engine height, and pitch of the prop in relation to what your load is. Also play with the trim.
Dave
DaveOriginally Posted by Blackened
I have got the motor height and trim set to the point where the prop will cavitate when turning the boat. Just have no way of checking my engine RPM to work out which way to go with the prop.
thanks Craig
what size prop have u got now? pitch, ill compare it to my very simaller boat
besides being shiny, what is the real advantage of SS props? they certainly won't help with cavitation, that's more of a height and trim set-up issue isn't it?
is your 25hp on a pressed tinnie? there may be some some water disturbance around the prop. trim will depend on the internal weight in the after part of the boat.
anymore details on the boat, or photos, prop out of the box, etc.
Gelsec,
Stainless props are a higher performance prop. The steel being stronger than alloy means the prop can be thinner than alloy and with less flex than alloy. Thinner translates to less rotational resistance and hence less power bleed and less flex is likewise.
Whether a stainless prop on a small boat like that would result in a really noticeable performance gain is questionable. A gain absolutely, but how noticeable???
Many aluminium boats cavitate in turns and in my experience its usually due to the engine anti cav palte being set level with the bottom of the hull (but not leevel with the bottom of the keel extrusion). I have reset engines on tinnies to the bottom of the keel extrusion and resolved the cavitation issues. Although you could actually consider this to be ventilation since air is drawn into the prop flow whilst turning as it runs turbulently along the keel extrusion and into the prop.
Cheers
Hi there
The prop that came with the motor is 9/7eighth by11/1 quater
thanks Craig
BM, I agree about the physical differences between SS & alloy props, and heard all about about the high performance side of SS props, where do you need this high performance, which boats, what operating environment justifies the extra $$. Does it really apply across the board, does the average fishing type boat gain any real advantages from one, or has the hype conned lots of boaters into buying them. I'm sure the manufacturers would disagree, and no doubt there's circumstances where a SS is warranted, but shiny sure does attract the bower birds.
roddo
my mate has a 4.2mtr with a 30hp yammy and tried the ss prop and made jackshut diff to the boat , so my advice to you is go up to a 10x13in prop or the nearest to that your motor will take as it will give you a bit more in the top end.
pickers
Ummm.... Gelsec, please take your seat at the top of the class
You are dead right that its about throwing money at something and about feeling better than the next guy etc etc etc waffle waffle waffle...
Yes, stainless props are better and if you took the performance aspect out of it and looked at pure economics you could probably assert that a stainless prop will increase your fuel economy. But a $1000 prop and any improvement in fuel economy would still translate to a lot of fuel and your stock ally prop...
Now to me (and I copped it recently on fishnet for this) economy is not really important. Boating for me is relaxation therapy and I don't really care (within reason obviously) what I spend on a days outing. If you go on a charter boat its $100 plus for the day per person.... I will not control my on water movement by how much fuel I am going to use. Granted, I am not talking heading mega miles off shore, I am talking the regular embayment/close inshore fishing that the great majority would do on a regular/semi regular basis.
Back to the topic.... oops.... you are right that for the average fisho a stainless prop is not going to do a lot for his boat other than make him feel a bit better and have a hole in his pocket from the cost.
Oh yeah, hit something with a stainless prop and its generally BYE BYE gearbox.... Alloy, at least you snap blades.
Cheers
Have a read of this info from Boat props aus.
Tony
How about a stainless steel prop?
Outboard propellers made from stainless steel are strong, stiff, and expensive ... that's the reality.
Stainless steel props perform accordingly ... simple, honest and brutal.
Yes brutal ... as in heavy. Listen to the grinding noises followed by the "clunk" as you engage a gear. The engine struggling to overcome the substantial inertia of the heavy stainless steel outboard propeller.
Watch your rpm as you climb out of the hole, your motor slower, spinning the heavier flywheel now residing on the propeller shaft.
Brutal as in it doesn't break easily ... it just tends to break everything else around it except the rock or the stump your stainless steel outboard propeller just struck. The prop won’t bend much, neither will the rock.
Your hardened steel propeller shaft on the other hand ... actually it won’t bend much either ... it will just TWIST OR BREAK.
What would you rather break when you go boating? ... an outboard propeller or a propeller shaft?You can fit a propeller which is cheaper by a long shot so it makes sense to choose a cheaper outboard propeller every time.
How about an aluminum propeller?
Aluminum is light, much more forgiving than stainless steel and far less expensive ... particularly if it's a "Power" outboard propeller.
It's a fact that aluminium marine propellers grace the driveshafts of practically every style of outboard or sterndrive powered pleasure boat or fishing boat right round the world.
If it’s an outboard propeller ... made of metal and painted ... it’s probably made of aluminum.
In fact ... aluminium is almost as commonly used in outboard propellers as rubber is in car tyres. It’s the industry standard.
So ... an aluminium prop is a good compromise and quite satisfactory for an outboard propeller ... if you operate in deep water.
But if the water is not deep ... or if you operate in a waterway which is likely to damage your Aluminium outboard propeller ... or if you want protection for your lower unit ... there is another option.
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"Piranha Propellers". </B>
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Do you ever dream about a better system ... perhaps wishing you could repair your own outboard propeller?
An outboard propeller you could repair yourself ... no matter where you are?
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All that would make you so independant it would seem like a dream ... but why not extend the dream a bit further?
While you're at it ... why not have an outboard propeller which won't cause or suffer from rust, corrosion or electrolysis?
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roddo I bought a handy tacho/hourmeter $60 from a mob called christie engineering(on the net) you just wrap a lead around a spark plug lead ,and the little digital display reads rpm when running and shows hours when engine is not running.its got its own little battery easy to hook up and you can more it around to other engines if you want.I also found solas props great to deal with to getting the best out of boat set up.
Sounds similar to the Pro Pulse plastic propellers with adjustable pitch and repalceable blades.
Has been a complete flop in the market from my understanding....
Bad hull design should not be compensated by similar thinking....Many aluminium boats cavitate in turns and in my experience its usually due to the engine anti cav palte being set level with the bottom of the hull (but not leevel with the bottom of the keel extrusion). I have reset engines on tinnies to the bottom of the keel extrusion and resolved the cavitation issues. Although you could actually consider this to be ventilation since air is drawn into the prop flow whilst turning as it runs turbulently along the keel extrusion and into the prop....
hi how do you find ya trolling speed is as i have the 385 as well with a 25hp tohatsu on it and mine trolls to fast
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