Reply
 
Thread Tools Search this Thread
 
Old 08 May 2008, 05:17   #1
Member
 
Country: UK - England
Town: Radstock
Boat name: No name yet
Make: flatacraft
Length: 3m +
Engine: 25
Join Date: Mar 2006
Posts: 9
Old Yamaha 40hp outboard problem

Hi I wonder if someone can help me with a problem I am having with a old Yamaha 40hp outboard.

The engine starts OK and revs OK in neutral but when I put it in gear it never reaches max revs, it seems to me that the revs under load only reach about half way.

I have stripped the carbs and gave them a good clean, I have replaced the spark plugs, used new fuel.

Can any body help me ?

Regards,

Martin.
__________________

__________________
Berty123 is offline   Reply With Quote
Old 08 May 2008, 05:33   #2
Member
 
Country: Netherlands
Town: Holland
Make: Brig F360S
Length: 3m +
Engine: Yamaha 70hp
Join Date: Jan 2008
Posts: 85
What boat is it behind and what prop are you using?
__________________

__________________
reinier is offline   Reply With Quote
Old 08 May 2008, 05:49   #3
Member
 
Country: UK - England
Town: Radstock
Boat name: No name yet
Make: flatacraft
Length: 3m +
Engine: 25
Join Date: Mar 2006
Posts: 9
Hi Thanks for the reply.

The boat is an old inflatable of ancient origions.
The Prop is unknown.
The engine performed very well as it was but one day it just wouldn't rev high enough when placed in gear. I have cheked and the prop is undamaged.

Regards,

Martin.
__________________
Berty123 is offline   Reply With Quote
Old 08 May 2008, 13:18   #4
RIBnet admin team
 
Nos4r2's Avatar
 
Country: UK - England
Town: The wilds of Wiltshire
Boat name: WhiteNoise/Dominator
Make: Ballistic 7.8/SR5.4
Length: 7m +
Engine: Opti 225/Yam 85
MMSI: 235090687/235055163
Join Date: Jul 2005
Posts: 12,645
RIBase
Have you checked for a spark on both plugs?


Don't rev it in neutral-it'll bugger it and it's no indication of engine health as it'll hit the redline on one cylinder.
__________________
Need spares,consoles,consumables,hire,training or even a new boat?

Please click HERE and HERE and support our Trade Members.

Join up as a Trade member or Supporter HERE
Nos4r2 is offline   Reply With Quote
Old 08 May 2008, 17:57   #5
Member
 
spartacus's Avatar
 
Country: UK - Scotland
Town: Aberdeenshire
Boat name: Sula
Make: Ribcraft 4.8m
Length: 4m +
Engine: Tohatsu 60hp + aux
MMSI: 235087213
Join Date: Jun 2007
Posts: 3,267
RIBase
You need to rule out a few things, so you can pin-point the problem. There are a multitude of things it could be. If you've cleaned carbs and used fresh fuel and sparks then - you should have seen some difference. Did you adjust anything on the carbs?

Ruling that out:

Check: fuel filter on engine block. Commonly overlooked but can clog up.

Check: sparking for both cylinders? (also check leads and ignition coils)

Check: Ignition sequence and timing correct?

Check: Do you have good compression on both cylinders?

Check: fuel pump operating normally?

Check: all wiring tight, no corroded terminals?

Last but not least - fuel tank vented properly?
__________________
spartacus 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 10:23.


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