repacement prop required help

[Daniel TD5]

i want to change my prop to a stainless steel type to cut cavatation in tight
turns down when the prop loses grip

ive been told a alloy prop will not grip as well as ss type and are much better
in the water all round

my engine is a 50hp 2003 mercury elpto which as a unknown prop fitted

down the side is the numbers 4873136a40 13p i think hard to read to much paint

it will rev at 5900 wot which is a bit high so could be dropped a bit
i don,t need to go any faster or carry more weight the boat is fine apart from the turns

so what ss prop do i go for how much are they were do i find the best deal

all i know is i think its a 13

any help or contacts

i am all so off to see mickey mouse in the states in jan so is it worth getting
a mercury prop out there ive seen then at about $100 on the net would any one know the part numbers of replacement ss mercury props

thanks dan

[Nasher]

Dan

Give Steel developments a ring, the owner is a very helpful bloke with a wealth of knowledge. Number is on here somewhere, as well as a link to his website.

Nasher

[Daniel TD5]

i am going to send my old one back to them for a refurb after a fit my new one are there new ss props as good as the mercury ones ?

[Wayne Rogers]

Don't turn Dan.problem solved.

[Wayne Rogers]

Sorry Dan, on a serious note I recieved an E-Mail from boats and outboards last week,some guy who breaks outboards is selling of a load of stock, I have deleted the E-Mail but will look at site for you.There you go mate found it, good luck.


Bill Higham Marine
The Chapel, City Road, Worsley, Manchester
M28 1BD
Tel: 0161 790 7678
Web: http://www.billhigham.co.uk

[DJL]

Dan,

You’re suffering from ventilation in the turns not cavitation. As you go round the corner the prop moves closer to the surface and air then gets sucked into the prop resulting in a loss of grip.

A stainless prop won't solve your problem, although it may recover a fair bit quicker. I suspect you’re not trimming the engine in far enough during the turn. However if you still experience ventilation when the engines fully trimmed in then you might want to try lowering the engine on the transom.

Don't let me put you of a SS prop though. They do perform much better generally; however I wouldn't expect it to solve your problem. As Nasher says give Steel developments a ring. http://www.steeldevelopments.co.uk

From that serial number I would guess its a 13" pitch

[Hightower]

Daniel



I'd be blowed if I can tell the difference between my 17" SS and 17" Alloy prop. They are both Michigan wheel props the SS one being the raptor and the Alloy being a "Match" direct replacment one. Engine revs slightly higher with the Alloy but top end speed and handling are identical!
I guess on a sub 100hp Rib it dosn't make that much differance really, or if it did would it be worth the extra money for the gain in performance?

Not in my case anyway! I was told by my service centre that if you had an underwater collision with a SS prop, it'll be a new gearbox but much less likley with a Alloy prop. Reason enough to stick to Alloy props.

Andy

[Searider]

Hi Daniel and Dan,

Daniel,

I have had a much better experience when I went from an aluminium prop to a Stainless one on my 5.4m Searider with a 90hp. Was suffering from ventilation/cavitation/loss of grip in turns and at high speed when trimmed right out.

Changed from a 19" aluminium standard prop to a 20" SS Laser II. The difference was incredible. Could turn much tighter, could trim the engine up as much as I wanted without losing grip.
The point is that the Laser II is a high rake propeller with a large amount of cupping on the trailing edges of the blades and is designed to run in aerated water near the surface. I feel that this is why it works well, not necessarily because it is SS.

My Scorpion has a 19" SS Mercury Vengence prop at the moment. This seems to ventilate / cavitate a fair bit under certain circumstances. Over the next season I shall be looking to try some alternative props - probably 19" and 21" Laser IIs to see if there is any improvement.

There were other issues with my aluminium prop. There were numerous fractures in the blades that may have been allowing flexing and had I changed to a new aluminium prop this may also have restored the performance to what it was when I bought the boat.

So, Dan, is your current aluminium propeller in good condition? If not, then it might be worth getting it overhauled by someone such as Steel Developments. In any case this can't do any harm.
If you want to bring your revs down a bit then you need to increase the pitch. By how much, however, is where the guesswork starts. Many will quote rules of thumb of about 1" reducing rpm by a few hundred and if going from aluminium to stainless to add an inch on top of that.
In my experience in going from a 19" aluminium to a 20" stainless made no difference in the maximum rpm.
So maybe try a 15" stainless prop with lots of cupping.
Or a selection of secondhand aluminium ones from Bill Higham might work?

Finally, a shiny stainless prop looks fantastic and we must not forget that one of the reasons for having a boat is in the pride of ownership.
Never underestimate the importance of bling!

If you can get a cheap Mercury ss prop when you go to the States then why not? There is some information on Mercury props on the mercurymarine.com website.

Regards

[Bilge Rat]

Originally Posted by Searider

Finally, a shiny stainless prop looks fantastic and we must not forget that one of the reasons for having a boat is in the pride of ownership.
Never underestimate the importance of bling!

If you can get a cheap Mercury ss prop when you go to the States then why not? There is some information on Mercury props on the mercurymarine.com website.

Regards

If this is the case then why not just spray your ally prop silver best of both worlds then, the "bling look" (if thats important to you) and a prop that wont wreck your gear box when you hit the bottom

[Daniel TD5]

Originally Posted by DJL

Dan,

You’re suffering from ventilation in the turns not cavitation. As you go round the corner the prop moves closer to the surface and air then gets sucked into the prop resulting in a loss of grip.

A stainless prop won't solve your problem, although it may recover a fair bit quicker. I suspect you’re not trimming the engine in far enough during the turn. However if you still experience ventilation when the engines fully trimmed in then you might want to try lowering the engine on the transom.

Don't let me put you of a SS prop though. They do perform much better generally; however I wouldn't expect it to solve your problem. As Nasher says give Steel developments a ring. http://www.steeldevelopments.co.uk

From that serial number I would guess its a 13" pitch

i looked at were the engine was mounted and set up. the engine can not be lowered at all as its sitting on the transom and i checked the mercury install guide and it meets that and i don,t want to cut the transom down so a stainless steel seems to be the way to go for improving the turns

thanks dan
my alloy prop may be damaged but not that i could see it look in good nick

[swginn]

Dan,

Was talking to my Merc engineer today and got some part numbers for you (see end of reply)

If you haven't read the first article below then this is where you should start!! Explains the difference between ventilation and cavitation, and also explains slip, cupping, rake, pitch, diameter, skew, number of blades, blade thickness, etc. You're probably going right now but give it a read, its very interesting!!

Everything you wanted to know about props:
http://www.mercurymarine.com/everyt...out_propellers5

After that if you're thinking of buying a prop in the States (and I suggest you do, you'll save a sh#t load!!) then look at the following:

The Mercury range of props:
http://www.mercurymarine.com/props

The following 13" props may suit your needs. The part numbers are in brackets. The Trophy Sport is a 4 blade prop, it grips better in tight turns, reduces steering torque and improves handling. The Vengeance is a 3 blader which also improves handling and acceleration.

Trophy Sport 13"
(48-878614A40)

Vengeance 13"
(48-855858A5)

These are the 14" variations of the above.

Trophy Sport 14"
(48-878616A40)

Vengeance 14"
(48-855860A5)

Your existing prop part number (48-73136a40) is a 13" Black Max which is definitely one of the better alu props available.

HTH!!

[Searider]

Originally Posted by Bilge Rat

If this is the case then why not just spray your ally prop silver best of both worlds then, the "bling look" (if thats important to you) and a prop that wont wreck your gear box when you hit the bottom

Fair comment about the "Bling"

Not quite convinced about the "SS prop will wreck your gearbox when you hit the bottom" though.

Most of the wrecked gearboxes I see at work (assessing insurance claims) are Volvo Penta Sterndrives with aluminium props. I reckon if you hit the bottom at speed with any propeller you may well wreck your gearbox.

Some of the Mercury stainless propellers are available with rubber hubs that should reduce the risk of damage in the event of an impact.

Need to make sure that the prop has the correct hub size for the engine in question - but if buying from a Mercury dealer this should be OK.

I've got a Vengence and don't rate it - I think that it's the cheapest of the Mercury stainless props which is why the previous Owner fitted it.

I would try out a / a few second hand / borrowed props if at all possible before splashing out on a new stainless one even if it can be had at a good price. As a guide I paid £115 for my secondhand Laser II against nearly £300 new.

Regards

[Daniel TD5]

Originally Posted by swginn

Dan,

Was talking to my Merc engineer today and got some part numbers for you (see end of reply)

If you haven't read the first article below then this is where you should start!! Explains the difference between ventilation and cavitation, and also explains slip, cupping, rake, pitch, diameter, skew, number of blades, blade thickness, etc. You're probably going right now but give it a read, its very interesting!!

Everything you wanted to know about props:
http://www.mercurymarine.com/everyt...out_propellers5

After that if you're thinking of buying a prop in the States (and I suggest you do, you'll save a sh#t load!!) then look at the following:

The Mercury range of props:
http://www.mercurymarine.com/props

The following 13" props may suit your needs. The part numbers are in brackets. The Trophy Sport is a 4 blade prop, it grips better in tight turns, reduces steering torque and improves handling. The Vengeance is a 3 blader which also improves handling and acceleration.

Trophy Sport 13"
(48-878614A40)

Vengeance 13"
(48-855858A5)

These are the 14" variations of the above.

Trophy Sport 14"
(48-878616A40)

Vengeance 14"
(48-855860A5)

Your existing prop part number (48-73136a40) is a 13" Black Max which is definitely one of the better alu props available.

HTH!!

thanks your a diamond

looks like the trophy sport is the one so what would be the difference between a 13 and 14 inch

dan

[Bilge Rat]

Searider.... fair comment, for me a stainless prop would be a waste of money as i go through so many props i'd be devistated destroying a £275 stainless prop and know doubt running true to form it would be the first trip out, where we operate it gets very shallow with moving sand banks and muscle beds, plus we tend to try and use the entire tidal range which means crawling in and out of the harbour with only minimal clearance under the hull, coupled with lobster and crab pots, the odd beer keg and jet skiier it makes it easy to dig a prop.

[swginn]

Dan,

First of all 5900rpm is way too high for that engine. It should be revving to 5500 rpm max. This isn't a bad thing though, it just means that you'll gain more performance by fitting the correct prop.

The Trophy Sport is a 4 blade prop. 4 and 5 blade propellers versus 3 blade props usually:

- plane the boat faster.
- Keep the boat on plane at a lower speed.
- Improve mid-range speed at the same RPM
- Provide quicker acceleration than most 3 blade propellers
- Operate with less vibrations
- Have better holding capabilities in rough conditions
- Are less likely to ventilate in (sharp) turns
- Provide better low speed handling
- Are not quite as fast on the top end as a comparable 3 blade propeller

This should solve yor turning problem, now you have to drop the revs. Upgrading from a three blade to a four prop generally drops revs by 50 to 100. So this should get you down to 5800RPM. Also the change from Alu to Stainless should drop your revs even more because of the added weight (I am not sure on this one so maybe somebody else who has gone from alu to stainless can advise!!) so lets say you are now at 5700RPM

You said above that you do not want go any faster, but running a 13" 4 blader will in fact slow you down. Although theoretically any two 13" props should travel 13" in one revolution, a 4 blade prop is actually less efficient than a 3 blader and so will travel a shorter difference and therefore be slower. Changing the the prop pitch to 14" should enable you to keep your top speed and will also drop your revs by another 200 to about 5500RPM.

This is within the correct WOT range for your engine!! So if it were me I would be going for the 14" Trophy Sport (48-878616A40). Double check this with your Merc Dealer obviously!! In theory it works but I don't want you to go shelling out your hard earned on something that doesn't work.

Plenty of bargains to be had in the states!! Don't bring it back as hand luggage (I know you'll be tempted!) I would imagine a prop can be quite sharp when flung out of an overhead locker, OUCH!!

Hope this all made sense!! (or have I confused you even more!!)

[Daniel TD5]

thanks swginn

i will check with my dealer to see if he thinks its a good choice i will say i want to get it from him it may be that
its not a uk part as i have never see any and most ss props are stocked items are for larger engines only but in the states they will be well cheap

i will try to email some dealer near were i am going to check stock

dan

[swginn]

Its definitely a UK part. My dealer can get one and he's supplied by Barrus. Steel Developments have them for £329, ouch!! Thats more expensive than a Laser 2 but I suppose you are paying for an extra blade!!

[Daniel TD5]

what i will do is take both part numbers listed below to the states and check the price

Trophy Sport 14"
(48-878616A40)

Vengeance 14"
(48-855860A5)

- plane the boat faster.
- Keep the boat on plane at a lower speed.
- Improve mid-range speed at the same RPM
- Provide quicker acceleration than most 3 blade propellers
- Operate with less vibrations
- Have better holding capabilities in rough conditions
- Are less likely to ventilate in (sharp) turns
- Provide better low speed handling
- Are not quite as fast on the top end as a comparable 3 blade propeller

all sounds to good to be true my rib is goes about 32 knots which is as fast as i want to go


as you say a 14" would be better to lower the revs that what my dealer said ss will all so drop rpm and he said try a 14" i would think he would supply the
vengeance to be a replacement

the price i found for the tropy plus on the net which is the next one up i think was $329.99 i think that about half in pound which will be under £200 notes

will you see what your dealer would recomend as mine is not to hot on props

dan

[Bilge Rat]

Dan.......Stop and think about all this for a moment, your running off on this prop issue before you've even replaced the missing anode onto the lower leg.

Suggest you take one issue at a time, re fit the anode and try the boat in differing conditions, if your still getting ventillation or slippage then explore the prop issues, think about how your'll fill if you run out and spend shit loads on a stainless prop you didn't actually need in the first place.....more to the point think about trying to explain this to Kel as she's gona kill you mate

[swginn]

Dan,

Was talkin to my Merc engineer today, while booking the Opti in for her service. I explained your situation to him. He said that something didn't sound right and that it sounds like your engine was set-up too high and to bring it in and he'll sort it for you. (Then I explained where you were!!) They've set up plenty of Ribcrafts, Zodiacs and Valiants with Merc 40/50/60 2strks and have never needed to change the prop from the standard alu one.

Fair enough the stainless prop may sort all your problems, but it also might not. I personally would like to have the engine set up right first before I went tinkering about with props. The temptation is there to get a nice shiney stainless one, but this may not be the answer.