Reply
 
Thread Tools Search this Thread
 
Old 29 November 2004, 10:58   #11
Member
 
Country: Ireland
Town: Carigaline/Baltimore
Boat name: XS-600
Make: XS-Ribs
Length: 6m +
Engine: Merc Optimax 150 XL
Join Date: Feb 2004
Posts: 682
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!!
__________________

__________________
Steve G
If In Doubt, Go Flat Out!!
swginn is offline   Reply With Quote
Old 29 November 2004, 11:56   #12
Member
 
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 10hp Yam / 150hp opt
Join Date: Sep 2003
Posts: 1,894
RIBase
Quote:
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
__________________

__________________
Searider is offline   Reply With Quote
Old 29 November 2004, 13:30   #13
Member
 
Country: UK - England
Town: london
Boat name: Frances May
Make: vailant DR450
Length: 4m +
Engine: mercury 50 hp
Join Date: Sep 2003
Posts: 761
Send a message via Yahoo to Daniel TD5
Quote:
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
__________________
GET A RIB GET A LIFE
Daniel TD5 is offline   Reply With Quote
Old 29 November 2004, 16:29   #14
Member
 
Country: UK - England
Town: Whitstable
Boat name: Tango
Make: Avon and Narwhal2.4m
Length: 4m +
Engine: 60HP Yamaha
Join Date: Oct 2002
Posts: 966
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.
__________________
Bilge Rat is offline   Reply With Quote
Old 30 November 2004, 12:58   #15
Member
 
Country: Ireland
Town: Carigaline/Baltimore
Boat name: XS-600
Make: XS-Ribs
Length: 6m +
Engine: Merc Optimax 150 XL
Join Date: Feb 2004
Posts: 682
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!!)
__________________
Steve G
If In Doubt, Go Flat Out!!
swginn is offline   Reply With Quote
Old 30 November 2004, 14:09   #16
Member
 
Country: UK - England
Town: london
Boat name: Frances May
Make: vailant DR450
Length: 4m +
Engine: mercury 50 hp
Join Date: Sep 2003
Posts: 761
Send a message via Yahoo to 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
__________________
GET A RIB GET A LIFE
Daniel TD5 is offline   Reply With Quote
Old 30 November 2004, 14:19   #17
Member
 
Country: Ireland
Town: Carigaline/Baltimore
Boat name: XS-600
Make: XS-Ribs
Length: 6m +
Engine: Merc Optimax 150 XL
Join Date: Feb 2004
Posts: 682
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!!
Attached Thumbnails
Click image for larger version

Name:	TrophySport.jpg
Views:	180
Size:	22.7 KB
ID:	9482  
__________________
Steve G
If In Doubt, Go Flat Out!!
swginn is offline   Reply With Quote
Old 30 November 2004, 14:48   #18
Member
 
Country: UK - England
Town: london
Boat name: Frances May
Make: vailant DR450
Length: 4m +
Engine: mercury 50 hp
Join Date: Sep 2003
Posts: 761
Send a message via Yahoo to 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
__________________
GET A RIB GET A LIFE
Daniel TD5 is offline   Reply With Quote
Old 01 December 2004, 03:51   #19
Member
 
Country: UK - England
Town: Whitstable
Boat name: Tango
Make: Avon and Narwhal2.4m
Length: 4m +
Engine: 60HP Yamaha
Join Date: Oct 2002
Posts: 966
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
__________________
Bilge Rat is offline   Reply With Quote
Old 01 December 2004, 05:22   #20
Member
 
Country: Ireland
Town: Carigaline/Baltimore
Boat name: XS-600
Make: XS-Ribs
Length: 6m +
Engine: Merc Optimax 150 XL
Join Date: Feb 2004
Posts: 682
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.
__________________

__________________
Steve G
If In Doubt, Go Flat Out!!
swginn is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 00:58.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.