Cavitations

[TPD]

hi guy

I have a 14.5' fibreglass boat with a johnson 60 hp V4 that i bought recently and gave found that if you roll the throtle on to quick it just revs up and doesnt accelerate. if you back off and aply the throtle again, t takes off. it always ad this problem.

i put on aset of thos hydro foil wings thingy to get the boat to sit level, not that it had a problem i just had a set sit around. i noticed an increse in speed and it gets up on the plane quicker. but now i cavitates when your going along at about 3/4 throtle the water was pretty calm

i was just wondering i this normal. i asked at a boat shop, they just told me the engines old and its not worth spending money on it. there nothing wrong with the motor as far as i know and came with a complete spare motor.

any information or link to other post would be greatly apprecatied.

thanks

 

[Dunaruna]

Re: Cavitations

It's ventilating, not cavitating.

Sounds to me like you have a spun prop hub, does the rubber look perished? Where is the vent plate in relation to the bottom of the hull?

 

[5150abf]

Re: Cavitations

Define "hydro foil wing thingy" is this something you put on the motor or they attached to the hull of the boat?

Sounds to me like your motor may be a little too high, the foils or tabs you put on are lifting the back of the boat out of the water farther than normal causing the prop to suck air, try dropping the motor a hole and see if that makes a difference.

 

[tashasdaddy]

Re: Cavitations

i think you need to check your prop, draw a line across the hub, then use it and see if the line is still lined up. sounds more like a spun prop. get the Hydro off the motor, if you have planeing problems, put a set of smart tabs on it.

 

[TPD]

Re: Cavitations

Thanks for the feed back

As for the "hydrofoil thingy". hydro foil is written on them, they bolt to the bottom of the motor and follow the same line of the hull. type hydro foil into eBay under the boat category, there should be heaps.

These made a difference. the boats quicker gets on the plane easier.

I assuming that the ventilation is where I bolted the hydro foil to the motor? this is just level with the bottom of the boat at the back. The motor can be lowered about an 1 ? inches?

I?ll make mark the prop and hub to see if it slipping. But the funny thing is if you keep it flat out it won?t do it.

What are smart tabs?

Thanks again guys.

 

[tashasdaddy]

Re: Cavitations

try the prop first.

 

[Cricket Too]

Re: Cavitations

I agree get the "Hydro-Foil" or "Dol-Fin" whichever it is called off there. There are more of a pain then they are worth. It is probably causing the extra lift and making your prop ventilate. Plus I always thought they put a lot of extra downward force and strain on the lower unit.

I'd agree with everybody else, sounds like you have a bad prop hub.

 

[steelespike]

Re: Cavitations

Is the prop in excellent shape.A new prop may sollve the venting problemYou should remove the foil and fine tune the boat,motor height,trim, moter well tuned ,throttle opening all the way.may need to get the new prop in order to get her set up.The foils are ok but can create as many problem as they solve.
Get it setup then consider the foil.Something like Smart Tabs are better.

 

[TPD]

Re: Cavitations

yeah the props pretty worn. looks like it had a hard life. i've swapped with the spare one. it a bit average itself but better than the one that was on it. haven't had a chance to try yet due to the weather.

i'll let you no how this prop go's mite just buy a new one...

thanks again guys.

 

[rodbolt]

Re: Cavitations

v4 60?
indicates its old as dirt and I rather agree with your tech. at least he is honest.
keep a good water pump and vernatherm in it keep a good fuel pump diaphram in it and run it.
this engine wont tolerate overheats at all.
is the shift mechanism in the gear case electric or mechanical?
either way test the prop hub.
if its an electric shift DO NOT hammer the throttle and dont pull skiers.
most the electric shift coils are no longer avalible nd havent been for quite some years.
also if its electric shift make sure the correct oil is in it as mechanical shift oil will cause the clutch coils to slip.
other than gas hogs that motor wasnt bad in either shift version just most parts are simply no longer avalible.