Motor Cavitation
Quick question.
I changed my prop about 12 months ago due to a spun prop bush. the bloke I bought the new prop off said it was exactly the same(pitch size) as the damaged one and to replace it was easy just do it up as tight as possible plus a little bit more. and obviously in the right order. ever since then I have been getting a bit of cavitation when taking off fast, turning sharp or just in everyday chop of the coast. its a 90hp johnson 2000 model ocean pro sits on roughly 24knots at just over 5000rpm. should i be getting more top end out of it and whats the best way to fix the cavitation, change the prop again or or put a cavitation plate on?
All advice apreciated.
Thanks
Still trying to catch fish!
West Coast Eagles Supporter and Proud Member.
carnarvonite
Posts: 8669
Date Joined: 24/07/07
Set up
Did the old prop cavitate or is it only the new one doing it? If its only the new one someting has changed, what caused the old one to spin the rubber bush?
If you picked up something of ran aground something has been knocked out of whack or IS the new one the same pitch like he says.
Aaron Santos
Posts: 300
Date Joined: 12/11/10
The old one was just wear and
The old one was just wear and tear and had never been changed in its life. I think what caused the old one to finally fail was a trip I did to rotto where I may had been a bit over loaded. it started to cavitate on the trip back about 2 km out of freo. since I have had the boat I have never hit anything or ran aground. Ive had the boat serviced and the leg all checked at the report came back all good. If i was to put a larger prop on would it fix the cavitation and give me more top speed or would it not make much difference?
Still trying to catch fish!
West Coast Eagles Supporter and Proud Member.
Bluedog
Posts: 251
Date Joined: 28/07/11
I have the same
I have the same year/make/model outboard and at 5000rpm on my Fraser 525 i'm going flat out and into the 30's on a nice day. My prop is 13 1/4 x 17. I usually cruuise around in the 3500-4500 range. I only ever really suffer cavitation when it's pretty lumpy and the boat is being thrown around a bit.
fishy fingers
Posts: 1719
Date Joined: 28/04/07
is it at the correct height
if it's too high on the transom you will get cavitation espescially when doing sharp turns, where is the cavitation plate in regards to the keel?
strike_zone
Posts: 403
Date Joined: 09/09/10
more revs
you should be getting more than 5000rpm more like at least 5800 try going to a lower pitch prop and watch a improvement in overall performance
nico
Posts: 226
Date Joined: 17/08/10
sound like your are over
sound like your are over proped have a look for numbers on the washer befor the lock nut or on the prop it self will be 17 or 19 x sounds like you need to go down in size especially if the blow out cavitation did not occur with the old one as strike zone said you should be hitting higher revs as well.Adding a hydrofoil to the cav plate is a after thought last option when all else fails.
In Mocean