Why am i getting cavitation
 

Hi guys

Just joined this group and hope you can help.

This weekend,i was out on my boat( Bayliner 2052,yr2000,4.3 merc efi )
which i know can reach 50mph
but i was struggling to get 40mph out of her and was cavitating bad
with a little water also being sprayed upward.

There is a small ring missing from the end of the prop/leg but i'm not
sure how or if this would effect things.The prop(standard) is
reasonable with a couple of dings but nothing serious and no change
since i could get 50mph out of her.

The trim gauge doesn't work either,but,knowing that the leg is down
and a standing full throttle start,after several seconds i start to
slowly raise the leg and before i know it,its cavitating and have to
close the throttle again. Its most annoying. Also,any tips on good
trimming,cheers.

Any help on this matter would be very apprecaited.
Thanks for reading.

Simon

Why am i getting cavitation
 

gilly wrote:
Hi guys

Just joined this group and hope you can help...

This weekend,i was out on my boat( Bayliner 2052,yr2000,4.3 merc efi )
which i know can reach 50mph
but i was struggling to get 40mph out of her and was cavitating bad
with a little water also being sprayed upward.

There is a small ring missing from the end of the prop/leg but i'm not
sure how or if this would effect things.The prop(standard) is
reasonable with a couple of dings but nothing serious and no change
since i could get 50mph out of her.

The trim gauge doesn't work either,but,knowing that the leg is down
and a standing full throttle start,after several seconds i start to
slowly raise the leg and before i know it,its cavitating and have to
close the throttle again. Its most annoying. Also,any tips on good
trimming,cheers.

Any help on this matter would be very apprecaited.
Thanks for reading.

Simon

Cavitation or ventilation? My guess is ventilation.

Well, you have compound issues now. Get it all fixed(prop
reconditioned["reasonable" as you call it is not really acceptable],
"ring"[assuming you mean the diffuser ring] replaced/repaired, trim
gauge repaired) and you will be back to where you started.

It all has to work together to get the performance you expect.

Rob

Why am i getting cavitation
 

"gilly" wrote in message
ups.com...


This weekend,i was out on my boat( Bayliner 2052,yr2000,4.3 merc efi )
which i know can reach 50mph...snip


Just curious..........how do you know that?

Why am i getting cavitation
 

On Aug 7, 1:24 pm, gilly wrote:
Hi guys

Just joined this group and hope you can help.

This weekend,i was out on my boat( Bayliner 2052,yr2000,4.3 merc efi )
which i know can reach 50mph
but i was struggling to get 40mph out of her and was cavitating bad
with a little water also being sprayed upward.

Out of curiosity what prop are you using ... e.g 21"? And what's the
max rpm you're achieving? Don't know, but I'd think with the 4.3 efi @
220hp, you just might get 50mph.

Why am i getting cavitation
 

JimH wrote:
"gilly" wrote in message
ups.com...

This weekend,i was out on my boat( Bayliner 2052,yr2000,4.3 merc efi )
which i know can reach 50mph...snip


Just curious..........how do you know that?


That's what he was told by the seller...

Rob

Why am i getting cavitation
 

which i know can reach 50mph
but i was struggling to get 40mph out of her and was cavitating bad
with a little water also being sprayed upward.

The trim gauge doesn't work either,but,knowing that the leg is down
and a standing full throttle start,after several seconds i start to
slowly raise the leg and before i know it,its cavitating and have to
close the throttle again.

If you have been getting 50mph, but are now getting 40mph, then the most
likely thing that has changed is that you have bent the aluminum(standard)
prop by hitting a sandbar...assuming that you aren't trimming up too high
now. A bent prop can reduce the prop pitch and/or cause
ventilation/cavitation).

Knowing what your trim angle is would help you for maximizing and repeating
the proper angle that you determine for best trim, so getting that fixed
would be nice.

If you can't get rid of the ventilation by fixing the prop, or getting a new
stainless one that won't bend every time you hit a sandbar, then you can get
a hydrofoil mounted on the outdrive. I have a mercruiser 4.3/alpha one and
the hydrofoil completely eliminated the ventilation I was getting.

Why am i getting cavitation
 

On 8 Aug, 00:48, "JimH" ask wrote:
"gilly" wrote in message

ups.com...



This weekend,i was out on my boat( Bayliner 2052,yr2000,4.3 merc efi )
which i know can reach 50mph...snip

Just curious..........how do you know that?

My first trip out on her showed 50-51mph on the gauge when i opened
the throttle.


Simon

Why am i getting cavitation
 

Gene Kearns wrote:
On Wed, 08 Aug 2007 16:36:51 -0700, gilly penned the following well
considered thoughts to the readers of rec.boats:

On 8 Aug, 00:48, "JimH" ask wrote:
"gilly" wrote in message

ups.com...



This weekend,i was out on my boat( Bayliner 2052,yr2000,4.3 merc efi )
which i know can reach 50mph...snip
Just curious..........how do you know that?
My first trip out on her showed 50-51mph on the gauge when i opened
the throttle.


Simon

If that is the case, Bayliner will probably buy the boat back! That's
about 10 MPH higher than they claim........ (except with the V-8)

Gene,
It probably is reading 50 mph on the speedmeter, but it does not mean he
is actually going 50 mph, the pressure tubes are extremely inaccurate.

Why am i getting cavitation
 

On 9 Aug, 15:32, Gene Kearns
wrote:
On Thu, 09 Aug 2007 10:09:48 -0400, Reginald P. Smithers III penned
the following well considered thoughts to the readers of rec.boats:



Gene Kearns wrote:
On Wed, 08 Aug 2007 16:36:51 -0700, gilly penned the following well
considered thoughts to the readers of rec.boats:

On 8 Aug, 00:48, "JimH" ask wrote:
"gilly" wrote in message

egroups.com...

This weekend,i was out on my boat( Bayliner 2052,yr2000,4.3 merc efi )
which i know can reach 50mph...snip
Just curious..........how do you know that?
My first trip out on her showed 50-51mph on the gauge when i opened
the throttle.

Simon

If that is the case, Bayliner will probably buy the boat back! That's
about 10 MPH higher than they claim........ (except with the V-8)

Gene,
It probably is reading 50 mph on the speedmeter, but it does not mean he
is actually going 50 mph, the pressure tubes are extremely inaccurate.

Yeah.... you are correct. I implied that inaccuracy in my 1st post.

--

Grady-White Gulfstream, out of Oak Island, NC.

Homepagehttp://pamandgene.idleplay.net/

Rec.boats at Lee Yeaton's Bayguidehttp://www.thebayguide.com/rec.boats

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So guys,surely the point is..... i'm only telling you that i saw 50mph
on my first trip(i'm not saying i was doing 50mph) and now its only
showing 40mph with a stuggle.So, something is wrong to be losing
10mph.This is what i'm trying to find out.
Now i've got myself a brand new prop with diffuser ring which is
missing on mine and a new trim gauge on order.I'm hoping this will
sort things out or at least go some way.

Simon

Why am i getting cavitation
 

On Fri, 10 Aug 2007 08:36:11 -0400, Gene Kearns
wrote:

Try this calculator. It might give you a broader picture of what you
are trying to accomplish.
http://continuouswave.com/cgi-bin/propcalc.pl/

How much slip should one use in that calculation.