Reply
 
Thread Tools Search this Thread
 
Old 14 January 2013, 17:30   #1
Member
 
pow2gran's Avatar
 
Country: UK - England
Town: Newcastle, Staffs
Boat name: Just Looking
Make: Ribcraft 5.85
Length: 5m +
Engine: Suzuki 140hp
Join Date: Jan 2011
Posts: 384
Jack Plates

Having read about jack plates in PBR I was wondering whether one would improve the flow of water around my Tohatsu 60hp. I suffer from excessive water splashing up onto the rear of the tubes and also onto the engine cowl. The following photos were taken a little while ago. I have fitted a stainless prop which has made a bit of an improvement. I have tried all the different heights the engine can be set on the transom. None have made any real difference. I could imagine a jack plate that set the engine back by 4 inches and put the prop in cleaner water would work. I would appreciate any comments
Attached Thumbnails
Click image for larger version

Name:	P1020373.jpg
Views:	142
Size:	70.6 KB
ID:	75518   Click image for larger version

Name:	P1020379.jpg
Views:	175
Size:	108.4 KB
ID:	75519  
__________________

__________________
pow2gran is offline   Reply With Quote
Old 14 January 2013, 17:58   #2
Member
 
Country: UK - England
Town: Gloucestershire
Boat name: Osprey
Make: Osprey Vipermax
Length: 5m +
Engine: E-tec 300 G2
MMSI: TBC
Join Date: Dec 2006
Posts: 4,013
Quote:
Originally Posted by pow2gran View Post
Having read about jack plates in PBR I was wondering whether one would improve the flow of water around my Tohatsu 60hp. I suffer from excessive water splashing up onto the rear of the tubes and also onto the engine cowl. The following photos were taken a little while ago. I have fitted a stainless prop which has made a bit of an improvement. I have tried all the different heights the engine can be set on the transom. None have made any real difference. I could imagine a jack plate that set the engine back by 4 inches and put the prop in cleaner water would work. I would appreciate any comments
When you have the engine trimed out does it still do this?
__________________

__________________
---------------------------------------------------
Chris Stevens

Born fiddler
Chris is offline   Reply With Quote
Old 14 January 2013, 18:15   #3
Member
 
pow2gran's Avatar
 
Country: UK - England
Town: Newcastle, Staffs
Boat name: Just Looking
Make: Ribcraft 5.85
Length: 5m +
Engine: Suzuki 140hp
Join Date: Jan 2011
Posts: 384
I have tried most permutations and all trim levels.
__________________
pow2gran is offline   Reply With Quote
Old 14 January 2013, 18:16   #4
Member
 
Country: UK - England
Town: Gloucestershire
Boat name: Osprey
Make: Osprey Vipermax
Length: 5m +
Engine: E-tec 300 G2
MMSI: TBC
Join Date: Dec 2006
Posts: 4,013
When your engine is trimmed fully down (in) where does the plate above the prop sit in relation to the bottom of the hull?
__________________
---------------------------------------------------
Chris Stevens

Born fiddler
Chris is offline   Reply With Quote
Old 15 January 2013, 09:04   #5
Member
 
Locozodiac's Avatar
 
Country: Other
Town: Lima-Peru
Boat name: Nautile
Make: Sea Rider Boats
Length: 4m +
Engine: Tohatsu 18 /30 HP
Join Date: Sep 2007
Posts: 1,706
Probably you have a long shaft engine sitting on a short shaft transom, looking at both pics engine sits too low, water flow hits the upper small plate, where the splash is produced. It's not a prop issue, its' rather an engine/tail height issues.

What you should do is make a large metal plate to sit on transom so to have a stright transom. Would be faster than filling the middle transom cut with wood, resin, fiberglasss ? Check pics for understandig. Water flow must pass under the small water deflector plate, this is the sweet spot, gives best engine top speed, superb performance & impecable tight turns at any water conditions.

This is what you should aim to achieve once engine sits well on transom :



Happy Boating
Attached Thumbnails
Click image for larger version

Name:	3-Tohatsu Tail.JPG
Views:	367
Size:	66.6 KB
ID:	75537   Click image for larger version

Name:	4-Ideal Water Flow.JPG
Views:	230
Size:	66.0 KB
ID:	75538   Click image for larger version

Name:	02.JPG
Views:	209
Size:	71.1 KB
ID:	75539   Click image for larger version

Name:	04.JPG
Views:	200
Size:	67.2 KB
ID:	75540  
__________________
Locozodiac is offline   Reply With Quote
Old 16 January 2013, 15:23   #6
Member
 
Country: UK - England
Town: Looe
Make: Delta
Length: 4m +
Engine: Mercury
Join Date: Apr 2004
Posts: 1,335
Yeah, looks just like its to deep in the water. But you said on the phone you have tried raising the engine height?
__________________
Black Dog Marine
www.blackdogmarine.com
Turbodiesel is offline   Reply With Quote
Old 16 January 2013, 16:00   #7
Member
 
Country: Germany
Town: StPetersburg Russia
Boat name: Black Hawk
Make: OSPREY Vipermax 7m
Length: 7m +
Engine: ETEC G2 250 H.O.
MMSI: 211579640
Join Date: Aug 2009
Posts: 397
RIBase
Send a message via Skype™ to Bushrider
Quote:
Originally Posted by Locozodiac View Post
Water flow must pass under the small water deflector plate, this is the sweet spot, gives best engine top speed, superb performance & impecable tight turns at any water conditions.
Looks strange and too low to me .. my best results I achieve when the A-cavitation plate is slightly above the water surface when the boat is on plane ..
__________________
Bushrider is offline   Reply With Quote
Old 16 January 2013, 16:59   #8
Member
 
pow2gran's Avatar
 
Country: UK - England
Town: Newcastle, Staffs
Boat name: Just Looking
Make: Ribcraft 5.85
Length: 5m +
Engine: Suzuki 140hp
Join Date: Jan 2011
Posts: 384
The engine has been set up as it says in the manual as shown in the picture below. I have taken the engine up two holes on the transom which is 17.5mm increments each time. It did not make any real difference but when it was two notches higher the prop cavitated when turning at speed.

I thought that the use of a jack plate would allow the prop to run in cleaner water. I would also be able to raise and lower the height to see if I could optimise the position of the motor in relation to the transom.

I have also fitted dolfins but that also didn't make a difference.

Something I feel is not right. Is it just the Tohatsu and would another outboard perform in a similar way? A jack plate is obviously cheaper than changing the outboard.
Attached Thumbnails
Click image for larger version

Name:	Outboard.jpg
Views:	174
Size:	77.2 KB
ID:	75585  
__________________
pow2gran is offline   Reply With Quote
Old 16 January 2013, 17:50   #9
Member
 
Country: UK - England
Town: macclessfield
Boat name: Reach Out
Make: Quicksilver
Length: 4m +
Engine: 30hp Tohatsu EFI
Join Date: Aug 2010
Posts: 301
How far is the bottom of the anti ventilation plate/dolphins above or below the keel line on your setup now?

Jack plates can sometimes compromise the tilting of the motor out of the water... As they can hit the transom when fully out...
__________________
simsy is offline   Reply With Quote
Old 16 January 2013, 18:04   #10
Member
 
pow2gran's Avatar
 
Country: UK - England
Town: Newcastle, Staffs
Boat name: Just Looking
Make: Ribcraft 5.85
Length: 5m +
Engine: Suzuki 140hp
Join Date: Jan 2011
Posts: 384
The ventilation plate sits around 20mm below the keel.

I see what you are saying about when on tilt, but I think it will clear the transom
__________________

__________________
pow2gran is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 19:55.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.