Mercury Vengence Propellor - slight cavitation

[J2DAG83]

Morning Gents

Just after some feedback (should anyone have any).

I have a vengence prop (17p) currently on my 175hp optimax, ever since i've owned it i have this issue where sometimes out of the blue the engine will start reving a bit higher and speed will drop... some form of cavitation i would assume.

An example would be cruising along at 4400rpm could be rough or calm it doesn't seem to discriminate doing say 50km/h and then all of a sudden the revs will climb to 4600rpm and the speed will drop by say 5km/h, basically i have to either drop revs and climb back up again or sometimes trim in a bit and wait for it to grab again so to speak (trim angle is not excessive to begin with)

My question is i have emailed solas with my issue and the response was that

" what you are describing is actually capitation and in this case its because the blade area is a tad small for the 175 MERC opti on that style of boat.

Its quite a common problem with the vengeance blade geometry. The best blade geometry to match and carry the boat better in solas is the saltist "

Basically i was just wanting to know if anyone has had a similar problem and rectified it by installing a new prop????? i have no issue with getting a new prop just don't really need to dump 700 odd bucks just to get a spare prop should it not fix the problem.

Oh and i've checked heights etc and they seem fine and i never have full on cavitation issues.

Thanks in advance should anyone be able to shed a bit of light.

Cheers

Jared

[fisho8]

Just been through this process mate with my 175 opti I have cav marks on my skeg. When I took it in for a service the tech noticed it he took the boat for a run and it would slip on hard turns so I got rid of that prop and replaced it with an Enercita Prop. Fixed the cav problem and the hole shot out of the water is 10 times better and it does not slip going into hard turns at higher speeds anymore. Got the prop for a good price to they usually retail for $880 but I got mine for $700 best money I have every spent so far. The vengance prop put on that engine from factory is a tad too small.:)


http://www.mercurymarine.com/propellers/comp/enertia/

[chop duster]

vengence is an entry level prop. what sort of boat are we talking about.
your local mercury dealer should be able to lend you some others to try, we just had to pay the shipping costs for each prop we tried.
Enertia is a goody and is what we currently run compromise between grip and top end. Gives good stern lift.
Mirage is a good alrounder if not after absolute top end.
Rev 4 for a big heavy boat and grip is essential (although big and heavy prop can cause prop lean on a deep V and hard on gearbox).
Could go on and on as we have tried them all..

[hard2catch]

I was having the same problem with my Signature 610c/175 opti with a Vengeance prop.I contacted Solas,they recomended a 4 blade prop as I mostly fish offshore.I am now running a 4 blade Rubex and it has not ventilated since,no matter how rough the conditions have been.

[J2DAG83]

Thanks for the replies fellas very informative and definetly what i was hoping to get...

Boat is a 6.4m sportsfish (old school).. might give the boys at wondall road a call and see if they can help out with letting me try a couple of different types.

Thanks again for the replies.

Jared

[chop duster]

see how you go, some dealers are not so friendly. Yer im thinking enertia or mirage would be the go. You got any speed to rpm figures to figure out prop slip? you will probably find the vengence has been slipping all the time and will have to step down an inch pitch or 2.

[fisho8]

Troy down at seaquest Marine let me try the enertia prop before I bought it no dramas at all if you have no luck with the others give him a call. Warren the tech down there knows the opti's inside and out and he recommended the Enertia to me for my boat but as said the may be another style you may need. they sell Solas down there to.:)

[J2DAG83]

I contacted Propellor Repairs Australia down the gold coast and explained everything that was happening.. basically as per above.. this was his reply....
"This problem is what we call 'slippage'. It is different to cavitation buit can have the same effect and the results would be exactly like having a slipping clutch in a car
It happens at cruising speed either when the blades lose grip on their own, when air is sucked from above the cavitation plate or when the boat gets a bit more lift [from a difference in water density]
bringing the blades closer to the surface.
All we have to do to fix the problem is to 'recup' the blades or sharpen the existing cupping
It only takes a full day to cup a propeller and costs will vary depending on the engine hp,material and amount of blades but for your info, cupping a 3blades 50-140hp aluminium propeller is usually between $25-$33.00 and $33.00-$38.00 for a sst propeller"

If this is true it is clearly a far cheaper option then to purchase another one... not sure of peoples thoughts on this but am thinking for the sake of ~$100 i can at least see and would think should it not work i'm not really all that worse off?????

Any thoughts????

Cheers

Jared

Oh and thanks again for the replies / advice

[robothefisho]

Sending your prop to Aus prop repairs will be the cheapest and best thing to do. Won't regret it.

[Chimo]

Hi Jared

The Gold Coast mob, Prop Repairs (Yan), do know their stuff and its not a lot of dollars either.

IMHO I'd give them a go.

Cheers
Chimo

[Fed]

Oh and i've checked heights etc and they seem fine and i never have full on cavitation issues.

Revisit your engine height.


Just been through this process mate with my 175 opti I have cav marks on my skeg.
How the hell does that happen Fisho?

[J2DAG83]

Thanks for all the replies fellas.... Will flick it off to old mate down the goldy and see what happens.

Will let you all know if it fixes the problem

Cheers

Jared