motor setup help

[bearessentials]

hi guys,
just recently i upgraded my old trusty 3cyl 30 hp yammie to a 3cyl 40 hp yammie (manual trim and tilt).
the boat it is fitted to is a 4.2 stessco catcher with a bit of extra weight added (front and rear cast decks), and a bow mount electric up the front.
the problem i am having is cavatation... i have played with the trim settings, and feel it is at its best at the 3rd hole from the top, currently the motor is on the 2nd hole from the top on the transom.
the motor was fitted by wynnum marine, so you can be assured that it wasnt a backyard fit up..
whenever i gun the motor hard out of the hole it starts to cav, but is fine if i apply the throttle smoothly. also when i try to turn with a bit of throttle still on she lgihts up also... for general use you would probably not notice it, but when i am trying to get back for the hat that has just blown off my head in a hurry it can be a bit painful..
currently i am hitting just shy of 30 knots at approx 5200 revs, the motor is rated for the 5000-5500 rev range max..
i am not aposed to buying a s.s prop if any one thinks it will help, but not sure what size or pitch would suit and at 500 bucks i wanna be sure...
thanks for reading my extended rant...
any info or suggestions are greatly appreciated..
cheers, bear essentials.

[STUIE63]

check the cav plate height first it should be just at water level whilst on the plane

[robothefisho]

Sounds like its set up just right for efficiency, except the rev range, would be good to see it higher. You can however get alloy props altered and cupped. Cupping gives you grip on the water, and is why ss props hang on better. (Without in depth explanation of blade shape etc)

[Jarrah Jack]

May also pay to give solas a ring. Agree 500 bucks is too much to spend if it not assured of working. Discuss it with them. Cheaper to get the blades from the states but that doesn't solve to origional problem.

[Kondo 1]

Hey Mate,

I had a 50hp yamaha with the same problem running a 12 inch yamaha prop, If I were you I would get solas to cup it, made a massive difference to mine.

I have always found the standard yamaha props are awful and cavitate massively (thats on both a 4 and 2 stroke 50's on 2 differnet boats) and the Solas props are much better especially if they are cupped.

Cupping is pretty inexpensive so a good place to start.

[bearessentials]

cheers guys, will give solas a ring

[bearessentials]

just rang solas... man do they know there props.... very helpful, will be buying a 13 inch prop from them, as i have plenty of power and will better my economy, just have to decide if i go for alluminium or stainless... any suggestions guys???

[Tickleish]

Hey Bear, i had a 3cyl 50 yammie and did the same thing you are going through.

I trialed a stainless prop but ended up with the alloy. I could not notice any real differance with hole shot or economy. Even my gps could only pick up a knot of differance at wot.

I also did alot of shallow creek work and the alloy was easier to put back into shape.

PS. the stainless ones do look tougher though.

[neil_stessco]

My stessco sf420 with 40 4stroke yamaha did that, It was set up in correctly ( 50MM ) too deep from the dealership so when i corrected that i couldn't take off or steer without bad cavitation, i had to use a stainless prop, the alloy prop was my problem.

[bearessentials]

solas quoted me $475 for a s.s prop, or $245 for a alloy prop... they told me that it wouldnt make a hell of alot of difference with either one as there alloy props are really cupped. $230 bucks will buy a few cartons of xxxx...

has anyone had any experience changing prop size? will be going from a 12 to a 13, and wondering how much difference it will make..

[jason p]

isnt that xxxxx now::) ;D

[dreemon]

solas quoted me $475 for a s.s prop, or $245 for a alloy prop... they told me that it wouldnt make a hell of alot of difference with either one as there alloy props are really cupped. $230 bucks will buy a few cartons of xxxx...

has anyone had any experience changing prop size? will be going from a 12 to a 13, and wondering how much difference it will make..


If your only getting 5200 rpm with the 12p dont go the 13p , what did solas say about your pitch? I would think they would almost sugest an 11 with heavy cup and that should reduce the cavitation prob and bring the rpm up, I had both alloy and s/s on my 40hp with not a huge diff, so go with the one that will assure a full esky, and just keep a better eye on your depth, it does take a long time to stop runnning it into sand banks and that, cheers