Reply
 
Thread Tools Search this Thread
 
Old 31 October 2012, 19:38   #11
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
A smaller engine will move better a larger boat than a shorter one, depending on your overall weight, could be applied to planing issues too. If usinha long shaft on a short shaft transom at full wot will have so much water splashing inside deck that you could use it as a summer pool...

The splash is produced because water flow is hitting and smashing the non cutting tail edge.

Happy Boating
__________________

__________________
Locozodiac is offline   Reply With Quote
Old 01 November 2012, 05:10   #12
Member
 
Country: UK - Wales
Town: abergele
Boat name: all mine
Make: ribtec 3m
Length: 3m +
Engine: tohatsu 9.8 hp 2st
Join Date: Sep 2012
Posts: 275
I'm a bit lost here I use a 3m sib and 6hp longshaft johnson, but I don't get water splashing into the boat, I would like a shortshat engine but for now I have to use what I have so how much should I raise my engine on the transom
slate
__________________

__________________
slate1234 is offline   Reply With Quote
Old 01 November 2012, 06:48   #13
Member
 
m chappelow's Avatar
 
Country: UK - England
Town: yorkshire
Boat name: little vicky
Make: avon ex RNLI
Length: 3m +
Engine: tohatsu
Join Date: Mar 2008
Posts: 2,310
Quote:
Originally Posted by slate1234
I'm a bit lost here I use a 3m sib and 6hp longshaft johnson, but I don't get water splashing into the boat, I would like a shortshat engine but for now I have to use what I have so how much should I raise my engine on the transom
slate
It's the shape of the leg on the Tohatsus that causes the splash back most other engine makers have different leg profiles and don't have problems
, there is a flat on the leg casting thats normally above the waterline that causes the splash everything else is pointy,

Mine only splashes back at displacement speed when up on the plane the boat lifts up so the flow of water then clears the flat part and it reduces the spray
, I fill in the flat in with a shaped block of wood and hold it in position with tie wraps.
Saw on a post a few weeks back about using foam pipe lagging slid on the top edge of the transom that helped someone .
I did make some spray deflectors that tie wrapped on to the leg out of thick sheet rubber something like a set of Doel fins .
Attached Thumbnails
Click image for larger version

Name:	image-637757715.jpg
Views:	145
Size:	44.1 KB
ID:	73747   Click image for larger version

Name:	image-2841584748.jpg
Views:	122
Size:	47.7 KB
ID:	73748  
__________________
m chappelow is offline   Reply With Quote
Old 01 November 2012, 16:23   #14
Member
 
Country: UK - England
Town: Winchester
Boat name: Raven
Make: Westerly 33/Avon 310
Length: 5m +
Engine: Mercedes 42 Toh9.8
Join Date: May 2009
Posts: 266
Quote:
Originally Posted by m chappelow View Post
It's the shape of the leg on the Tohatsus that causes the splash back most other engine makers have different leg profiles and don't have problems
, there is a flat on the leg casting thats normally above the waterline that causes the splash everything else is pointy,

Mine only splashes back at displacement speed when up on the plane the boat lifts up so the flow of water then clears the flat part and it reduces the spray
, I fill in the flat in with a shaped block of wood and hold it in position with tie wraps.
Saw on a post a few weeks back about using foam pipe lagging slid on the top edge of the transom that helped someone .
I did make some spray deflectors that tie wrapped on to the leg out of thick sheet rubber something like a set of Doel fins .
That is really interesting, I thought it was to do with the cavitation plates, I have just had a look at mine and low and behold, a flat slab on the front of the leg.

Does your block of wood really stop the splash back? If so i'm of to the patent office tomorrow, its a brilliant idea. Thanks

Ribtecer...
__________________
Ribtecer is offline   Reply With Quote
Old 01 November 2012, 16:25   #15
Member
 
Country: UK - England
Town: NW Surrey
Boat name: Lady Helen
Make: Avon
Length: 3m +
Engine: Out Petrol 3.5 & 15
Join Date: Aug 2011
Posts: 222
Too late to patent - already been publicised.
__________________
EnglishLes is offline   Reply With Quote
Old 02 November 2012, 12:35   #16
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
Tohatsu compared to Yam is a natural water splasher, it's their particular tail shape design, most portable models have their gear shift rod passing through the non edge portion, that's where the splash is produced at speed/plane. A 39-40 cm keel/transom height is mandatory to solve the problem forever. As all sibs don't have same diam tubes, a trial and error water test must be done to find the sweet height spot.

Happy Boating
Attached Thumbnails
Click image for larger version

Name:	Tohatsu Tail.JPG
Views:	293
Size:	66.6 KB
ID:	73791   Click image for larger version

Name:	4-Ideal Water Flow.JPG
Views:	166
Size:	66.0 KB
ID:	73792  
__________________
Locozodiac is offline   Reply With Quote
Old 07 November 2012, 03:04   #17
Spammer
 
Country: Canada
Town: Southern Ontario
Boat name: -Unknown-
Make: SeaMax
Length: 4m +
Engine: Merc/Minn Kota
Join Date: Mar 2012
Posts: 216
Hi all,
Seems to me the optimum engine placement on the transom is where the anticavitation plate is 3/4" Below the centre bottom of hull. Raising the top of the transom is not a hard thing to do to achieve the proper anticavitation-plate location. I know as I raised my transom 1 1/2". However, raising the sailing-boat long shaft type may be too much, but I would think it can still be raised enough to avoid the engine's flat spot area?
__________________
Nightfisher is offline   Reply With Quote
Old 07 November 2012, 09:06   #18
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
On a sailboat at non planing speeds not a real issue with that, the problems starts when trying to plane a sib/rib and engine is not correct height seated specially when using Tohatsu, Nissan, Mariner, Mercury portables, last 3 rebadged Tohatsu's.

Happy Boating
__________________
Locozodiac is offline   Reply With Quote
Old 09 November 2012, 10:15   #19
Spammer
 
Country: Canada
Town: Southern Ontario
Boat name: -Unknown-
Make: SeaMax
Length: 4m +
Engine: Merc/Minn Kota
Join Date: Mar 2012
Posts: 216
Hi all, Wasn't refering to Sailboating and the engine. Was refering to the general leg-extension size.. quite long compared normal long-shaft engines.
__________________
Nightfisher is offline   Reply With Quote
Old 09 November 2012, 11:39   #20
Member
 
m chappelow's Avatar
 
Country: UK - England
Town: yorkshire
Boat name: little vicky
Make: avon ex RNLI
Length: 3m +
Engine: tohatsu
Join Date: Mar 2008
Posts: 2,310
Quote:
Originally Posted by Nightfisher
Hi all, Wasn't refering to Sailboating and the engine. Was refering to the general leg-extension size.. quite long compared normal long-shaft engines.
Some engine manufacturers do an Exra /Ultra long shaft leg or saildrive for displacement sailboats & yachts or where i the propeller will airate or come right out of the water with the yawning action of a displacement boat going up and down in waves .

Some also have a lower gear reduction in the gearbox so that it can take a slightly larger or multi blade/ fan type propeller or have a finer pitch for pushing displacement or heavier boats with high transoms ,.where stopping power is more important than high speed .

Think they are classed about 5 inches longer than a normal long shaft
Short 15 inch
Long 20 inch
Extra/ultra. 25 inch .

First rescue I did was to an old couple who had a yacht with an extra long shaft engine the old type shear pin had snapped on the prop
he couldn't reach out far enough to replace the shear pin & he couldn't get the engine into the boat as he had security bolts instead of clamp screws .
__________________

__________________
m chappelow 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 09:36.


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