Basic's of replacing a propellor

Clipper · 11 May 2010, 03:24

Hi everyone,

I did a search and didn't find any specific answers, so im hoping for some wisdom from you good people.

I have never removed and replaced a prop, and as such am naive to what's involved. I am now looking at a stainless steel replacement for my 18hp tohatsu, and considering buying a second hand prop.

Q: Do you need anything other than the prop when replacing it (brushes, o-rings, clips)?
Q: How to remove the prop? by just removing the split pin should the prop come off?

extra Q: does a good stainless prop really make a difference with power/speed? or is just the pitch which dictates performance?

thanks in advance

Markyboyo · 11 May 2010, 03:47

I don't think that any performance gains would be noticeable on a 18hp engine. You are just more likely to damage the gearbox rather then the prop if you hit anything.
On a larger engine you may see a slight increase in speed or a drop of a couple of hundred RPM at WOT when going to a stainless prop of similar pitch/diameter over an alloy one.

Is it possible to get a stainless prop for a 18hp hatsu? I didn't think anyone made them that small but stand to be corrected??

Clipper · 11 May 2010, 04:02

they certainly do, an Australian company named Solas manufacture them, and do fairly well from what i've heard.

the prop is claimed to have helped achieve 35knots out of a thunder cat (twin hull SIB) with an 18hp and some adjustments to transom height.

I also have a light SIB and an 18hp and was hoping to get a bit more top end speed?

9D280 · 11 May 2010, 10:06

There are two methods of holding the prop on (three if you cound the small Hp "aux" type engines) - 2/3 involve a nut, it's just the method of stopping it backing off & dropping off the shaft that differs.

Really small / older engines the prop is usually held to the shaft with a shear pin, and held fro dropping off by a split pin through the hub of the porp. You'll be unlikely to find this method above about 8Hp, unless your engine is really really old, and definetly won't find it on a thru' prop exhaust type.

The most common is the split pin & castle nut. You may have have a splined washer between it & the prop. Depending on the engine there may be thrust washers at the "front" of the prop to get the correct spacing & transfer the force to the engine leg.

Some older Mercs used a tab washer with 4 tabs instead of the split pin. two "nodules" on the back of the prop engage in two of the tabs, the other two are bent round the nut.

Either way, the recommedation is to replace the split pin / tab washer with new. You could get away with re-use in an emergency, but it's not reccommended as repeated bending to & fro will weaken the metal (think of breaking a paper clip)

I'll leave the prop gurus to the stainless / ally discussion......

Dirk Diggler · 11 May 2010, 10:18

Quote:

Originally Posted by Clipper

they certainly do, an Australian company named Solas manufacture them,

I think you'll find Solas is a Taiwanese company!

Poly · 11 May 2010, 11:54

Quote:

Originally Posted by 9D280

Depending on the engine there may be thrust washers at the "front" of the prop to get the correct spacing & transfer the force to the engine leg.

And if the prop has not been off for a while/ever then you may find this is stuck to the old prop. Make sure you grease the relevant bits so its easy to get the prop and nut off next time.

I always make sure the engine is in neutral and stop the prop turning with a bit of soft wood between the prop and gearbox casing (if its too stiff to do by hand) - not sure if I'm just paranoid about accidentally starting the engine by turning it over or it is a real risk.

m chappelow · 11 May 2010, 12:25

Dont use copper based grease ,eg,copperslip ,to grease the prop shaft or splines or anything else on the outboard leg ,,,best use waterproof marine grease .otherwise galvanic action will make it corrode bad style .

Clipper · 12 May 2010, 05:54

cheers guys, thats is some great info.

9D280 thanks for the description I feel more confident to take the prop off now.

I will also stay clear of the copper based grease and get some proper marine grade stuff.

Will make sure the outboards in neutral and give it a go.

thanks people,

PS dirk diggler, I was sure i had seen an 'Australian made' logo somewhere on their products? however, I not surprised if in reality it is manufactured in Taiwan and just imported.

jyasaki · 12 May 2010, 16:01

Well, a bit of poking around shows their main site listing an e-mail address of "market@solas.com.tw"; Based on that I'd say they're based out of Taiwan.

jky