Reply
 
Thread Tools Search this Thread
 
Old 07 June 2017, 19:17   #1
Member
 
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 100hp Yam/150hp opt
Join Date: Sep 2003
Posts: 2,060
RIBase
Lightest 4hp or 5hp

Evening all.

I have just purchased the smallest RIB in the world - a Bombard AX2000 and have a 3.5hp Tohatsu 2 stroke for it. I had hoped it would plane with this engine and whilst I wasn't surprised it didn't with my 90ish kg was disappointed that it wouldn't with my much lighter teenage son driving.

I think I need a little more power whilst keeping the weight down.

So, what are the lightest:

4hp?

5hp?

(I'm not a fan of the OMC 2cyl 4hp engines)
__________________

__________________
Searider is offline   Reply With Quote
Old 07 June 2017, 19:23   #2
Member
 
Country: UK - England
Town: Retford
Boat name: Spy-sea-one
Make: Excel 435
Length: 4m +
Engine: Suzuki Outboard/25/4
Join Date: Oct 2011
Posts: 7,276
RIBase
Quote:
Originally Posted by Searider View Post
Evening all.

I have just purchased the smallest RIB in the world - a Bombard AX2000 and have a 3.5hp Tohatsu 2 stroke for it. I had hoped it would plane with this engine and whilst I wasn't surprised it didn't with my 90ish kg was disappointed that it wouldn't with my much lighter teenage son driving.

I think I need a little more power whilst keeping the weight down.

So, what are the lightest:

4hp?

5hp?

(I'm not a fan of the OMC 2cyl 4hp engines)
I would guess Suzuki have a look on Ron hale marine and compare
__________________

__________________
jeffstevens763@g is offline   Reply With Quote
Old 07 June 2017, 19:36   #3
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Tohatsu 9.8 2-stroke
Join Date: Nov 2007
Posts: 7,470
What's it rated to?
__________________
Fenlander is offline   Reply With Quote
Old 07 June 2017, 20:22   #4
Member
 
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 100hp Yam/150hp opt
Join Date: Sep 2003
Posts: 2,060
RIBase
4hp

Previous owner used a 5hp without issues.
__________________
Searider is offline   Reply With Quote
Old 07 June 2017, 20:22   #5
Member
 
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 100hp Yam/150hp opt
Join Date: Sep 2003
Posts: 2,060
RIBase
Quote:
Originally Posted by jeffstevens763@g View Post
I would guess Suzuki have a look on Ron hale marine and compare
I'm looking at used - so guessing 2 stroke.
__________________
Searider is offline   Reply With Quote
Old 07 June 2017, 20:35   #6
Member
 
Country: UK - England
Town: East Anglia
Boat name: Nimrod II
Make: Aerotec 380
Length: 3m +
Engine: Tohatsu 9.8 2-stroke
Join Date: Nov 2007
Posts: 7,470
I think your 3.5 will weigh about 13kg... going up to a 4 or 5hp will probably take you to 20kg. Is that too much for what you had in mind?

If it's OK then I quite like those Mercury/Mariner/Tohatsu 2-stroke 5hp that look the same as the 4hp models.

Like one of these...

__________________
Fenlander is offline   Reply With Quote
Old 07 June 2017, 22:47   #7
Member
 
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 100hp Yam/150hp opt
Join Date: Sep 2003
Posts: 2,060
RIBase
That should do it.

Yes - the tohatsu is about 14kg.
I had a 4hp yam 2 stroke a couple of years ago and although heavier was manageable.
Are the 5hps about the same weight?
__________________
Searider is offline   Reply With Quote
Old 07 June 2017, 22:58   #8
Member
 
Country: UK - England
Town: Sussex
Boat name: Bombard
Make: Aerotec 380
Length: 3m +
Engine: Mercury Mariner 15hp
Join Date: Jul 2010
Posts: 3,271
Aren't 4/5/6 all the same block/weight generally? If so go 6.
__________________
Max... is offline   Reply With Quote
Old 08 June 2017, 01:44   #9
Member
 
Rover310's Avatar
 
Country: USA
Town: Southwest Colorado
Make: Avon Rover 310 Aero
Length: 3m +
Engine: Evinrude 6hp 2 smoke
Join Date: Apr 2015
Posts: 57
Quote:
Originally Posted by Max... View Post
Aren't 4/5/6 all the same block/weight generally? If so go 6.
Depends on the make. My 90's Evinrude 6 hp shared the same displacement powerhead and parts group with the 8 hp, the only difference being a larger carb bore on the 8. They weigh the same. Only way to tell them apart from one another was the '6' or '8' decal on the back of the hood.

Whereas the 5 hp and smaller Evinrudes of similar vintage also shared a common powerhead/parts group with each other, those motors typically having built-in fuel tanks as part of the motor cover. The 6 & 8 use remote fuel tanks.
__________________
Rover310 is offline   Reply With Quote
Old 08 June 2017, 11:47   #10
Member
 
Country: UK - England
Town: Dartmouth
Boat name: Puffling
Make: Avon Rover 3.4m
Length: 5m +
Engine: Mercury 15hp
Join Date: Jan 2002
Posts: 402
Send a message via MSN to badbaws
have you got a floorboard as that makes a huge difference.

Get a second 3.5hp run in tandem.. I did this with two x yamaha maltas. i used to get 6 knots with one and got 13 knots with two of them, plus it was great fun!

Failing that get a yamaha or tohatsu 5hp as they are same weight as 4hp but single cylinder. Johnson use twin cylinder but are much heavier. normally 4/5hp same block and 6/8 same block Yam / Merc /Mar / tohatsu

I have had my Avon Redseal planning with a 5hp and that is with the round transome and bracket. It did have floorboards.


RIBnet Forums - badbaws's Album: wake - Picture
__________________

__________________
Advanced Power Boat Instructor
badbaws 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




All times are GMT. The time now is 04:06.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.