4.3 merc slipping or cavatation?

[Muff424]

I have a 94 crownline 18' 4.3. I am trying to figure out why out of the hole it will slip. And send the rpm screaming? once back in neutral i can ease up to plane. Is this a fluid problem in the outdrive. I noticed the fluid level was lower when i took the boat out of the water. Or is it simply cavatation?

 

[QC]

Re: 4.3 merc slipping or cavatation?

Sounds more like ventilation. Trim all the way down to start? Can you make a full speed run? Do you have another prop to test?

 

[Reel Poor]

Re: 4.3 merc slipping or cavatation?

Did this happen after a prop change?

 

[Muff424]

Re: 4.3 merc slipping or cavatation?

What do u mean by ventilation? I am going to try another prop. It has a 21 pitch on it right now. I was thinking of putting a 19 on it.

 

[QC]

Re: 4.3 merc slipping or cavatation?

Do you already have the 19? If not, hold on just a minute . . . don't buy anything until we can figure out what is right for your boat/setup. If you have another to borrow, or already have the 19, then by all means try it. However, if we are trying to find the right prop, then this is not the way to go about it. We need more info for that. Are you able to go full speed? If so, what RPM does she get to? What speed? GPS preferred.

Ventilation is the prop grabbing air off the hull or the surface . . . often called cavitation, they are two different things. I had a great prop that ventilated too easily, but it would fly once I got her going . . .

 

[Muff424]

Re: 4.3 merc slipping or cavatation?

I don't have the 19 pitch prop right now. I just bought the boat and it has a 21 on it. However the guy that sold it just put it on because he didn't haev a prop to go with the boat. I am looking to use the boat for wake boarding. I can stand to lose some top end speed. I had it to about 42 mph. I don't recall the rpm. I have only had it out once. And the problem with the slipping starte when i had more people in the boat.

 

[QC]

Re: 4.3 merc slipping or cavatation?

Well we need to know what RPM at WOT, full tilt, trimmed out correctly and loaded as you plan to use your boat, then we can discuss prop pitch. The slipping issue could be nothing but ventilation as mentioned, or a very serious issue. I lean toward the former as you are able to make a decent top speed and the serious issues would not get better with increased power on the prop . . .