2520 Cavitation issues

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jimjybe

jimjybe

Well-known member
Joined
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Messages
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Location
Bradenton Florida
Our 1998 2520 modified V has issues with cavitation when running with seas or passing other boats in their wake. It's really nice to pass someone only to have to stop to loose the cavitation! The boat has the original motor (OX66 225), an Armstrong bracket and a SS prop with 17-M stamped on it. We hope to upgrade motor before too long so do not want to spend a fortune on this, hoping for an easy fix. We have been putting up with the cavitation but it is getting old! Any ideas?
 
What hole is the motor mounted on? When it Cavitates, is you engine trim all the way down or in any particular setting when it happens? Have you ever been able to look at where you Cav Plate rides while on plane at say 4500 rpm? I'm thinking you either trimmed to much or the motor is mounted to high?? These are the first things that come to mind? I don't think the prop is your problem. What is your max RPM and speed at WOT?
 
I'm thinking you either trimmed to much or the motor is mounted to high??
Click to expand...

X-2 with putting emphasis on the trim to high. Parker has always mounted motors to low.

We need "GOOD" pixs to see the mounting hole situation.
 
Thank you for the replies,
The cavitation will occur at any trim position but not as easily with trim down and the tabs all the way up. The max rpm is only about 4800, it is an older engine (1998) so we run her between 3600 - 4200 for the most part. I believe the cause is when the bow lowers in the trough coming off the wake the prop rises in the wake where there is air. I know from windsurfing that the backside of a wave crest will cause you cavitation, but that is a little different situation, yet I wonder if the decrease in positive water motion will cause it with a prop? The motor is set in one hole from the top of the bracket (one hole from all the way down). The boat runs really well, plane's quick and is fast enough, probably is the main reason I have been ignoring the cavitation issue. Have also figured it may just be the "nature of the beast" because the prop is so far away from the transom. Since I live near the "prop gods" I may just need to call them, heck they may even know this boat.
 

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Pretty sure it is cavitating, but I could be wrong, no issues with a hole shot or running in any other direction. When I overtake a yacht I can tell you exactly when it will happen, if I slow down and plow through the wake with motor tucked under - no issues, except that it is hard to pass when you slow down. I should set up a go-pro camera to see it in action and tell exactly where my cavitation plate is running. The platform makes hard to see the lower unit but the last time I checked, from what I could see, the cavitation plate was inches below the surface. Never happens at speeds under 20mph, only at higher speeds when she is skipping like a rock.
 
I'm having a very similar problem with a 91 2310 WA. My motor is all the way down.
 
23ParkerWA":23poscfq said:
I'm having a very similar problem with a 91 2310 WA. My motor is all the way down.
Click to expand...
Do you have the same set up with bracket? and modified vee??
 
Your setup sounds similar to mine.
This is what I have:

1996 2520 MVSC (14 degree deadrise).
Stainless Marine bracket. Full transom.
1997 Yamaha OX66 (fuel injected).
End of model year hull, first year injected motor
Mercury Marine 17p stainless 3-blade prop
24x9 Bennett trim tabs (upgraded from 12x12 OEM).

Prior to raising the motor, max engine RPM's were only 5000, and that was on a 'spring' clean bottom.
Later in the season, the motor would only turn ~4900.
Photo #1 is the factory position of the motor, and yes, it would blow out in a turn if I wasn't careful and throttle down.

Photo #2 is the position of the motor now, and if I had it to do over, I would have raised it to that last hole.
Photo #3 and #4 are of the prop that I am wearing.

Boat will now turn 5100 RPM at WOT even late in the season.
Max speed now is ~33 to 34 knots depending on trim.
This motor should be turning 5500 RPM at WOT, so I'm still a little low.
However, I bought this prop from another person who had added a bit of cup to it. It is not a stock off-the-shelf prop.

Photo #5 is the overall view of the transom.
That swim platform was fabricated by the previous owner, and is not an OEM piece.

Since adding the larger tabs and raising the motor, the boat is much more responsive, quicker on plane, and exhibits no bad qualities.

Hope this helps.
 

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Megabyte said:
Your setup sounds similar to mine.
This is what I have:

1996 2520 MVSC (14 degree deadrise).
Stainless Marine bracket. Full transom.
1997 Yamaha OX66 (fuel injected).
End of model year hull, first year injected motor
Mercury Marine 17p stainless 3-blade prop
24x9 Bennett trim tabs (upgraded from 12x12 OEM).

quote]

It's hard to tell but it looks like your last photo show the cavi plate pretty level to the keel of your hull. That's where I'm told it should be.


Mine is already level with keel. I'm wondering if it's a prop problem
Click to expand...
 
23ParkerWA":36hi1zpy said:
It's hard to tell but it looks like your last photo show the cavi plate pretty level to the keel of your hull. That's where I'm told it should be.
Mine is already level with keel. I'm wondering if it's a prop problem
Click to expand...

If you are on a bracket, the cav plate should be a little above the keel.
 
Same setup as ours alright, Our platform is a little different (integrated aluminum) but the bracket is the same, and the prop . . well who knows. The last time we headed offshore it was calm, I could see that the cavitation plate was well under the surface. Maybe being too low in the water will cause it to cavitate? Can't help but think that someone has been there done that with this and it is the best it will get. The only other thing we have is the thru-hull transducer and raw water intake but they are well to the side of center-line, besides it will only do it when running with the seas.



Megabyte":qdfxc2yt said:
Your setup sounds similar to mine.
This is what I have:

1996 2520 MVSC (14 degree deadrise).
Stainless Marine bracket. Full transom.
1997 Yamaha OX66 (fuel injected).
End of model year hull, first year injected motor
Mercury Marine 17p stainless 3-blade prop
24x9 Bennett trim tabs (upgraded from 12x12 OEM).

Prior to raising the motor, max engine RPM's were only 5000, and that was on a 'spring' clean bottom.
Later in the season, the motor would only turn ~4900.
Photo #1 is the factory position of the motor, and yes, it would blow out in a turn if I wasn't careful and throttle down.

Photo #2 is the position of the motor now, and if I had it to do over, I would have raised it to that last hole.
Photo #3 and #4 are of the prop that I am wearing.

Boat will now turn 5100 RPM at WOT even late in the season.
Max speed now is ~33 to 34 knots depending on trim.
This motor should be turning 5500 RPM at WOT, so I'm still a little low.
However, I bought this prop from another person who had added a bit of cup to it. It is not a stock off-the-shelf prop.

Photo #5 is the overall view of the transom.
That swim platform was fabricated by the previous owner, and is not an OEM piece.

Since adding the larger tabs and raising the motor, the boat is much more responsive, quicker on plane, and exhibits no bad qualities.

Hope this helps.
Click to expand...
 
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