Simple Prop Maintenance 101
Ok our First Boat maintenance thread! Lets hope it works!
It is a good idea - to periodically take a look at your propellor and service it, in order to avoid potential drama's at sea and avoid expensive breakdowns / repairs.
Things can and do go wrong with propellors!
I hope this thread will assist folks to confidently take a peek at their own propellors and keep them in tip top shape for good performance, reliability and safety!
Why do we need to pull the prop? - it's working just fine!!...if it ain't broke - why fix it?
Well, what if it does break at sea, and you wish to put on a spare to get you back home?
If the prop is seized to the shaft...how hard will it be to fix at sea?
So..
One of the reasons we pull a prop is to clean and re-grease the spine shaft so it will come off again easily next time we want/need to do something to it!
Also - if it does get seized to the prop shaft thru corrosion and lack of grease, servicing, then getting it off COULD damag the prop or worse the lower unit gear case and pinion gears inside it as well, which can become a MAJOR expense to rectify!
So simple annual maintenance will help alleviate these sorts of drama's!
Any other reasons to pull the prop for a looksee?
Sure!
Checking the lower unit gear case waterproof seals!
These are subject to damage by tangled fishing line - it could be one of you're own you've inadvertantly run over while trolling at some point - it might be a shore or jetty anglers line you (or someone else driving your boat) ran over without even knowing it, or it could just be someone's discarded line that was just floating around the ocean which you never saw!
Any other good reasons to pull a prop?
Yes, there are more good reasons!
Props have some method of cushioning any impacts with the blades & solid objects (logs, rocks, reefs, coral etc) from damaging the drive train. These can be sheer pins or flow torque hub inserts in the case of some Mercury props, more common tho is a rubber hub bushing which is pressure fitted with a big press!
These are designed to "slip / tear" in the event of a collision with a solid immovable object to protect the internal mechanical drive train components!
However - these rubber bush inserts can and do perish / wear out with use / age! When they do wear out, the outer blade part of the prop - will slip around the rubber bush and inner drive hub!
Your engine will rev up and you will go almost no where! (Usually they will retain enough grip for you to make some headway at idle / displacement speed...but a 20 or 30 mile trip home in bad weather at 3knots can be VERY annoying / unsettling AND you may not have budgeted the fuel capacity to make such a trip with such loss of momentum due to slippage!)
So - we aim to know about an impending hub slip problem BEFORE it happens on the offshore trip to end all offshore trips!
Lastly, if you can't find the info anywhere else, often times you'll find the prop brand and pitch / diameter information stamped on the rear thrust face of the prop!
With this info and a little more as I'll show in another thread soon, we can calculate how efficiently our prop is performing and whether we are obtaining the best speed / fuel efficiency, from our particular prop setup!
So - while at first glance - pulling prop for a sticky beak and a little grease might seem like a waste of time and bit of unecessary tomfoolery, anyone who doesn't keep a close eye on their wheel / wheels is eventually asking for trouble at sea! Just as we need to keep an eye on the condition of the tyres on our car if we want trouble free motoring -we need to keep a check on our prop / props!
When was the last time you pulled your prop?
So read on if you would like to see how to do it yourself at little to no cost (other than a few hours of your time!)
Cheers!
Fly
Posts: 485
Date Joined: 04/02/06
Here we go!
The service I've depicted below is on a pair of yr 2000 Honda 115 hp 4 Strokes, with 500 ours on them. One is a counter rotating prop!
I've just shown the steps one prop in this thread!
I make a habit of only doing one prop at a time on twin prop setups!
Whys that?
Well - it is possible to mix the props up and replace the wrong one on the wrong engine - and if you do - your in heap big trouble paleface! ;o)
A right hand twist prop on a left hand twist lower unit will drive your boat backwards in forward gear - and likewise vice versa will do the same - mix em both up and forward gears become reverse gears on a boat and reverse become forward!
Now - you CAN drive a boat like this - with the gearshift setup bass ackwards...you can even swap the gear change cables over to compensate for reversed props..so the gear lever shifts the right way again BUT - your gear cases will still be running backwards while the boats travelling forwards! The reverse cogs in the lower units are NOT hardened to the same temper as the forward ones which normally do the bulk of the work - so you WILL chew out your lower unit gears if you were dumb enough to make such a mistake (and you would NOT be the first!)
For this reason I do one at a time - that way theres no chance of making that mistake!
The prop we are working on here, is a Solas stainless steel 3 blade left hand twist (i.e. counter rotating) 13 & 3/4 inch diameter x 15 inch pitch!.
It has a thru hub exhaust, and is a rubber hubbed model!
It is located on my port (left hand) engine!
Many would contend (And I would agree) that this as azz about face!
I.e - in a correct setup, in my opinion, the counter rotator (left hand twist)propellor SHOULD be located on the starboard engine!
There is a reason for this!
It is believed by those who claim to know, that when twin props turn such that the blades passing in the middle both travel downwards, the thrust of water between them pushing likewise downwards, tends to raise the transom of the hull slightly upwards, which results in less wetted surface area hence less drag hence more speed and less fuel burn!
I believe the difference to be minimal, and some spuriously claim that due to the 'correolis effect' (water going down the plughole anti clockwise compared to the northern hemisphere, cyclones rotating anti clockwise below the equator abd clockwise in the northern hemisphere) is reason enough to rig twin outboards on boats downunder bass ackwards, to how they are rigged elsewhere! ;o)
Anyway - I just think someone didn't know enough about it who hung these motors when the boat was built in Yr 2000.
So - it makes very little difference - but MIGHT improve performance / handling and fuel burn slightly if changed!
How to change it?
Well you dont just swap props over because the left hand twister has to twist left, and the right has to twist right as already explained!
So - you need to pull the lower units (like when you change water pump impellers...which is a subject of a soon to be written thread) and swap the entire lower unit from one engine to the other!
This is a fair bit of work, for only a minor gain.... maybe I'll do it next impeller change in 12 months time!
Cheers!
Fly
Posts: 485
Date Joined: 04/02/06
OK our first real step
Our First real step - is to remove the split pin (some in other nations call it a cotter pin) by straightening the two legs and pulling it out of the hole thru the prop spline shaft with a pair of pliers!
Thats quite straightforward!
Fly
Posts: 485
Date Joined: 04/02/06
Step 2
The next step is to take a look at the prop nut lock tab washer!
You will see it has 3 of it's 6 tabs bent down into the recesses on the reverse thrust washer!
Fly
Posts: 485
Date Joined: 04/02/06
Step 3
We need to gently bend these 3 tabs Up by placing a screwdriver blade under them and levering upwards gently until they bend up enough to clear the locking recesses. When we unscrew the castellated locking nut, the tabs washer has to rotate with the nut, due to its hexagonal recess the catsellated prop nut sits down into!!
You can see I've already bent the lower tab up!
In the photo below you can see how I used a screwdriver to do this!
Fly
Posts: 485
Date Joined: 04/02/06
Step 4
Step 4 is to remove the castellated nut!
Mine came off with my fingers, but if its tight you can use a socket wrench!
I cheated here coz mine came off with my onkaparinga's (phat Phingers) and I used the photo here, where I put it back on again with the socket wrench, but you get the idea!
Because mine was loose I havent shown it here - but theres a VERY important safety consideration here!
We do NOT want to inadvertantly crank our engine over with a socket wrench on the prop nut if it were left in gear - which if it turns the prop and prop shaft and thus turns the driveshaft and crankshaft and so on, COULD (IF THE IGNTION WERE LEFT ON!) accidentally start the engine up and cut us to ribbons on the prop, not to mention smacking us and our anti ventillation plate with the socket wrench bar etc etc..
So - before you do this - you should ensure your engine is:-
A) out of gear!
B) has the ignition off
C) if you wish to follow the manual - remove the spark plugs!
Now - if you do these things - how do you stop the prop from free turning to get the nut off, if it's tight?
Well - you should wedge a piece of pine softwood between one of the blades and the anti-vent plate to lock it from turning!
Fly
Posts: 485
Date Joined: 04/02/06
Step 5
Remove the castellated nut and lock tab washer!
I like to line them up in the order they came off on a clean flat surface for ease of reinstallation and to help me remember which order they go back on in!
Fly
Posts: 485
Date Joined: 04/02/06
Step 6
Remove the prop by hand!
Of course if you haven't done yours in the last 10 or 15 years - well that might be a little more difficult, in bad situations it might require the use of a prop pulling tool device if the prop shaft is seized to the spline of the prop hub!!
This is why we do this once a year to avoid that situation!
Fly
Posts: 485
Date Joined: 04/02/06
Step 7
Ok..You should of course get a reverse thrust washer and forward thrust washer come loosein your hands!
Line these up in the right order with your previous split pin, locktab washer, castellated nut, reverse thrust washer, prop, forward thruust washer!
Fly
Posts: 485
Date Joined: 04/02/06
Step 8
You will see that you are left with a dirty greasy prop spline shaft!
You may also notice (before anyone else points it out) in this pic -the forward thrust washer is still on the shaft...yet in the picture previous it's lined up with the goodies on the back deck! Lets just say it's trick photography! ;o)
Oops! ;o)
Fly
Posts: 485
Date Joined: 04/02/06
Step 9
Time to clean this greasy sucker!
Get the clean rag and make it dirty!
You should now have a clean spline which you need to inspect closely for any damage or advanced corrosion!
Fly
Posts: 485
Date Joined: 04/02/06
Right-oh, Step 10
We need to clean and then very closely inspect for any visible damage the spline shaft gear case waterproof seal. It is rubber, and subject to damage by fishing line and braid that might get tangled around your prop!
Should it leak and go undetected - you will rust out your lower unit gears and bearings with the saltwater sitting below the gear case oil, and this will lead to a lower unit failure under load - usually when your a long way offshore - you do NOT want this - take the time to clean and check it carefully!
Fly
Posts: 485
Date Joined: 04/02/06
Step 11
Clean inside the prop hub spline!
Check for any damaged bronze splines or signs of slippage where the soft bronze splines might have slipped over the harder stainless steel prop shaft splines! Also look for advanced signs of electrolysis / galvanic corrosion of the brass splines!
While your there look for any sign of the rubber hub perishing crumbling and about to fail!
You might also want to write down the make and prop specifications of your prop for later use in verifying your performance / fuel burn figures which are stamped into this rear face!!
Solas 13&3/4" Dia x 15" Pitch (L) (left hand twist!)
Fly
Posts: 485
Date Joined: 04/02/06
Step 12
Now spin the prop around and look in the other way...from the rear exhaust side!
Now you get a much better look at that rubber hub for signs of perishing / rupture / tearing and a closeup of the bronze splines too!
Fly
Posts: 485
Date Joined: 04/02/06
Step 13
Ok - now we grease it all up again with new marine waterproof grease!
Ready to put it all back together again!
Fly
Posts: 485
Date Joined: 04/02/06
Step 14
Grease up that forward thrust washer and the waterproof prop spline shaft/gearcase seal!
Fly
Posts: 485
Date Joined: 04/02/06
Step 15
Re-Install the forward prop thrust washer!
Fly
Posts: 485
Date Joined: 04/02/06
Step 16
Grease up the inside of that prop hub!
Then re-install it by hand!
I've cheated again here I've re-used the same photo of when I removed it! ;o)
Fly
Posts: 485
Date Joined: 04/02/06
Step 17
Now grease up and re-install the prop lock reverse thrust washer!
Fly
Posts: 485
Date Joined: 04/02/06
Step 18
Grease and re-install the prop nut lock tab washer!
Fly
Posts: 485
Date Joined: 04/02/06
Step 19
Grease and re-install the prop castellated lock nut!
Fly
Posts: 485
Date Joined: 04/02/06
Step 20
Nip it up just firm with the socket wrench and bar!
Same safety rules mentioned earlier apply here:-
a) Engine out of gear
b) Ignition off
c) Remove spark plugs
d) Block prop from turning with soft pine wood betwen prop blade and cavitation plate. (not depicted here!).
Fly
Posts: 485
Date Joined: 04/02/06
Step 21
Re-install the split pin in the castellated nut!!
Fly
Posts: 485
Date Joined: 04/02/06
Step 22
Make sure you bend the ends of the split pin down and back over the prop spline shaft respectively!
Also then it comes time to re-bend the lock tab washer tabs down into their reverse thrust washer lock tab recesses!
I use a screw driver and hammer to do this but if you have one, you can use a drift punch!
You are now good to go!
And - best of all, the only tools needed were a monkey wrench and ball pein hammer! ;o)
Cheers!
mitch
Posts: 1285
Date Joined: 14/08/05
cool diagrams
good stuff flywest .must of taken a bit of time to get photos etc and comments on this site . am looking forward to the impeller pics and your comments on how to do it
always in it just the depth that varies
Big Frank
Posts: 115
Date Joined: 07/02/06
Stainless steel props
The guy who services my boat says I can get more speed and better economy with a stainless steel prop. Does anyone know why ss is better? They are pretty hard on the pocket!
Great thread Flywest
Fly
Posts: 485
Date Joined: 04/02/06
Yes
Indeed your boat guy is correct Big Frank.
Stainless wheels have thinner and stiffer blades than alloy. For this reason, they have less resistanmce and more speed! As an alloy blade 'flexes' more it's pitch changes so it diesn't rmeain as "true" over all rev ranges!
The advantage of Alloy over stainless is in making contact with something solid! Reefs, rocks, boat ramps, logs, the curb when you back up without raising the outbards first! etc With an alloy prop you might bend a few blades but with stainless you are going to hurt your backpocket more seriously!
Then again, if most of your fishing is offshore with the cost of fuel these days - you might save the cost of the stainless wheel over the course of a year or two if you use theboat enough!
Everythings relative!
BOAT stands for "Break Out Another Thousand" - coz they are just a hole in the water you throw money into!!
As a great Philosopher once proclaimed:
With regard to your prop - the next thread might help you work out your efficiency of the prop you have now before you consider changing it to a stainless water wheel!
Cheers!