Reply
 
Thread Tools Search this Thread
 
Old 18 April 2016, 11:15   #21
Member
 
Country: UK - Scotland
Town: Argyll
Make: Tornado
Length: 5m +
Join Date: Sep 2011
Posts: 91
You may still have weak spark to give good idle and poor performance at higher rpm.
Swap coil and ignition HT lead, plug cap etc between 2 and 3. If you are lazy you might be able to just change the switch box trigger (coil input) from 2-3 and change the HT lead (coil output) from plug 2-3 (if it will reach) but undoing and re-making all connections including the coil ground to rule them out is not a bad thing.

If a timing issue, it seems odd that only one cyl is affected.
Are your three carbs identical - can you swap carb 2 for 3 for example? (do you have 3 carbs? my old mariner 70 did)

Do you have a timing strobe? Looks like you have seen that the manual has a value for correct timing at cranking speed, which will give you a good (enough) value at WOT if you are unable to test on the water; certainly a good enough value to run smoother than you have at present.

You could make two additional timing marks on the flywheel 120 degrees apart (or take the circumference and divide by 3), then trigger your strobe off cyl 3 HT lead. compare to 1 and 2 when running at some revs. This might highlight a weak spark if your strobe on 3 is much dimmer (fires less often) if you don't have a spark gap tester.

mariner test sequence is
1 - check input voltage to coils
2 - check for strong spark
3 - check spark plugs
4 - check timing: trigger/pickup linkage, trigger cable and plugs, trigger magnet ring
5 - check STOP circuit of switch box (ignition control box)
6 - check ignition switch - isolate stop switch/kill chord at the switch box (ignition control) and repeat stop circuit checks [edit: I had an old donkey engine with a weak spark caused by a wet and corroded kill switch]
7 - check stator

I presume you have the service manual and a multimeter to test the correct values?
__________________

__________________
steve-ribnet is offline   Reply With Quote
Old 18 April 2016, 11:18   #22
Member
 
Fstarocka's Avatar
 
Country: South Africa
Town: Cape Town
Length: 4m +
Engine: Mariner 60 3cyl 2str
Join Date: Jan 2016
Posts: 90
Hi tx, have timing light yes, I'll make diy spark gap tester, multimeter yes but not the one that can read Max volts..

Do I check input voltage to coils while running or cranking?

Got true tdc using piston stop and set cranking timing at 28 per manual.. Dropped it off with degrees for today's fuel..



Sent from my SM-G900M using Tapatalk
__________________

__________________
Fstarocka is offline   Reply With Quote
Old 18 April 2016, 11:29   #23
Member
 
Country: UK - Scotland
Town: Argyll
Make: Tornado
Length: 5m +
Join Date: Sep 2011
Posts: 91
Quote:
Originally Posted by Fstarocka View Post
Maybe sync link is way out? On front cover it says to set Max cranking degrees and then carb cam pickup just before the big slope to open carbs, but it doesn't specify whether to do that with Max stop touching or what...
for the 70/75/80HP, timing can be set roughly at cranking speed as 2 degrees more advance (before TDC) than your maximum advance timing value.

e.g. if your WOT maximum timing is 26 degree before TDC, then at cranking this will be 28 degree before TDC

Remove all spark plugs from block except #1, hold your timing control arm at max timing and against the screw stop and crank over on fresh battery. adjust timing stop screw to give your compensated maximum advance value
__________________
steve-ribnet is offline   Reply With Quote
Old 18 April 2016, 11:31   #24
Member
 
Fstarocka's Avatar
 
Country: South Africa
Town: Cape Town
Length: 4m +
Engine: Mariner 60 3cyl 2str
Join Date: Jan 2016
Posts: 90
Steve did that.. Wot timing is set perfectly.. So is Max throttle stop

Sent from my SM-G900M using Tapatalk
__________________
Fstarocka is offline   Reply With Quote
Old 18 April 2016, 11:45   #25
Member
 
Country: UK - Scotland
Town: Argyll
Make: Tornado
Length: 5m +
Join Date: Sep 2011
Posts: 91
Quote:
Originally Posted by Fstarocka View Post

Do I check input voltage to coils while running or cranking?
from the mariner 70 manual:
Test procedures and specifications are provided for
checking primary ignition voltage while the engine
is running and/or being cranked.

coil input (primary) voltage meter test range is 400volts DC, for a reading of 150-250Volts at cranking, 180-280 volts at 1000-4000RPM.

multimeters that handle 400VDC are cheap and plentiful in the UK - 35 will get you a Vichy VC99 clone).

You can check the stator coils with just an ohmmeter (resistance).
__________________
steve-ribnet is offline   Reply With Quote
Old 18 April 2016, 11:49   #26
Member
 
Country: UK - Scotland
Town: Argyll
Make: Tornado
Length: 5m +
Join Date: Sep 2011
Posts: 91
Quote:
Originally Posted by Fstarocka View Post
Steve did that.. Wot timing is set perfectly.. So is Max throttle stop

Sent from my SM-G900M using Tapatalk
good job. personally Id try swapping coils and HT leads over first before probing about, having first cleaned the plugs.
__________________
steve-ribnet is offline   Reply With Quote
Old 18 April 2016, 12:08   #27
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: 4,011
could be the coil. they can start to fail when they heat up
__________________
---------------------------------------------------
Chris Stevens

Born fiddler
Chris is offline   Reply With Quote
Old 18 April 2016, 12:50   #28
Member
 
Country: UK - Wales
Town: Here
Boat name: doggypaddle
Make: Avon 5.4 Searider
Length: 5m +
Engine: yamaha 80
Join Date: Jul 2007
Posts: 1,107
fuel pump diaphragm?

is the fuel pump diaphragm ok? may be worth checking if it connects to the crank case at the "wet "cylinder, they can fail and cause flooding, though usually more at low RPM.
__________________
I am usually not as green as i am cabbage looking.
doggypaddle is offline   Reply With Quote
Old 18 April 2016, 14:02   #29
Member
 
Fstarocka's Avatar
 
Country: South Africa
Town: Cape Town
Length: 4m +
Engine: Mariner 60 3cyl 2str
Join Date: Jan 2016
Posts: 90
Diaphragm is fine, also replaced all fuel lines ..

Sent from my SM-G900M using Tapatalk
__________________
Fstarocka is offline   Reply With Quote
Old 18 April 2016, 16:13   #30
Member
 
Country: UK - England
Town: Liverpool
Length: no boat
Join Date: May 2015
Posts: 93
Ive listened to the excellent little video clip again. I think its defo electrical. Cylinder drop test?? Nik
__________________

__________________
matata 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




Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 04:15.


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