Reply
 
Thread Tools Search this Thread
 
Old 25 April 2015, 17:35   #1
Member
 
Country: UK - England
Town: bristol
Boat name: c2
Make: bombard
Length: 3m +
Engine: tohatsu 25hp
Join Date: Jul 2010
Posts: 33
tohatsu 50hp timing and carb setup

Hello boaters.

I have a tohatsu 2 stroke 50hp 3 cylinder, on a zapcat.
Its actually mariner badged with gas tilt but identical engine under hood to my second engine which is the tohatsu badged m50d2.

Had some trouble with low speed, would bog down or stall when going into gear and pulling away. Would have to rev engine in idle let revs drop, bang it in gear and rev up quick to stop it stalling.once goin it planed but was lacking and wouldn't go flat out.

Engine was fine for about 45 mins before this started. Limped back to slipway, then few mins later gave it a blast and it seemed fine, got 40mph out of it.
Next day, lumpy low down to start but after an hour was ok.....? Annoying as can't trust engine without finding fault.

Need to check timing and carb jet sizes etc.

I cleaned the carbs months back and left them dry. Emptied fuel tank and lines, put in fresh fuel and measured oil exactly. Plugs new too. Coils all same resistance,, Thought it would run fine.


Any help or thoughts would be great
.thanks

Looking for a manual in any links or contacts or info, clymer, seloc, etc would be good.
__________________

__________________
Commando C2 is offline   Reply With Quote
Old 26 April 2015, 03:09   #2
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: 3,270
RIBase
I had a similar issue myself with a M60/70C outboard. If you've checked the carbs and they are spotless, ensure the butterfly choke operates properly. They are known to seize. The carb pilot screws should be adjusted too. Think it's one and a half turns out from lightly seated.

Scribd do some fairly comprehensive service manuals which should help you. There is one manual by Adrian Peterfi (1992-2000) that will include your model. Don't worry about the date.

Also, Roflhat on here knows the M50d2 like the back of his hand. You could PM him.
__________________

__________________
Is that with or without VAT?
spartacus is offline   Reply With Quote
Old 26 April 2015, 04:22   #3
Member
 
A1an's Avatar
 
Country: UK - Scotland
Town: Fort William
Make: Humber Destroyer
Length: 5m +
Engine: Yamaha F80
Join Date: Mar 2012
Posts: 2,239
RIBase
tohatsu 50hp timing and carb setup

Thinking logically it doesn't sound like a timing issue, if it was it wouldn't run fine one minute then rough the next then back to fine. That goes for jet sizes too, they are all a constant.

Sounds more like fuel related problem to me, when did you last drain fuel tank and carbs?
__________________
There is a place on this planet for all of Gods creatures.........right next to my tatties and gravy.
A1an is offline   Reply With Quote
Old 26 April 2015, 04:47   #4
Member
 
Country: UK - England
Town: bristol
Boat name: c2
Make: bombard
Length: 3m +
Engine: tohatsu 25hp
Join Date: Jul 2010
Posts: 33
manuals

Thanks Spartacus, I will look out for those manuals. I have heard some of them aren't accurate so don't want to end up making engine worse.
It is an ex rnli engine but has been owned by someone else since should have been setup properly just depends if previous owner tinkerered with it.

Will be pulling the carbs off anyway first.

Anyone know jet sizes? Akin last time I cleaned carbs there is a small rubber bung over the needle jet so can't understand how it gets to suck up fuel from float bowls?
__________________
Commando C2 is offline   Reply With Quote
Old 26 April 2015, 04:50   #5
Member
 
Country: UK - England
Town: bristol
Boat name: c2
Make: bombard
Length: 3m +
Engine: tohatsu 25hp
Join Date: Jul 2010
Posts: 33
I drained and cleaned the tanks a few days before using.the carbs got cleaned 6 months ago and not started or filled so carbs dry.
That's why I was expecting it to work.

Just want to check timing to cover all bases as the idle timing could be out.
__________________
Commando C2 is offline   Reply With Quote
Old 26 April 2015, 05:33   #6
Member
 
Roflhat's Avatar
 
Country: UK - Scotland
Town: Isle of Lewis
Make: Ceasar Thundercat
Length: 4m +
Engine: Yamaha 70ces
Join Date: Jul 2010
Posts: 633
RIBase
I had a similar issue, took me a long time to figure it out as it sounds like a fuel problem. Must have cleaned the carbs 10 times before I checked the coils. For me the engine would idle fine and rev in neutral, then bog as soon as you put it in gear and wouldn't rev properly at all. Turned out to be a bad coil, try taking the lead off each cylinder individually and see if they're all firing, the coils on the 50's are notoriously unreliable. In zapcat racing they're now allowed to swap tohatsu 70 coils, no performance gain just reliability.

I would doubt it could be the timing, I've tried all the settings possible without modifying the timing linkage arm and the engine idled fine with them all, the range is between 18-22 degrees at WOT I think? There's really no reason to adjust the timing beyond that

The D2's has 132 main jets if i remember correctly, they can be swapped out for 125's with slightly retarded timing but the gains are debeatable...

Let us know how you get on
__________________
Roflhat is offline   Reply With Quote
Old 26 April 2015, 09:34   #7
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: 3,270
RIBase
Rule out fuel related issues such as primer bulb (these can fail prematurely). Use Quicksilver part, not cheap EBay rubbish), fuel reservoir filter on engine, and fuel pump isn't leaking (worn diaphragm).
__________________
Is that with or without VAT?
spartacus is offline   Reply With Quote
Old 26 April 2015, 11:43   #8
Member
 
Country: UK - England
Town: bristol
Boat name: c2
Make: bombard
Length: 3m +
Engine: tohatsu 25hp
Join Date: Jul 2010
Posts: 33
Good info thanks. Will see how the carbs look.
I have some spare coils from my other engine that is running sweet so might swap them out. Going to add additional earth strap between coils too.

I did pull the plug lead off number 1, then start it and it felt the lead had a spark, then did same with other 2 so if one was down and one taken off it surely wouldn't start on one cylinder.?!

I think its not coil related as I was getting 40 mph out of it once it got planing....a duff coil normally shows up at top revs.
__________________
Commando C2 is offline   Reply With Quote
Old 26 April 2015, 11:48   #9
Member
 
Country: UK - England
Town: bristol
Boat name: c2
Make: bombard
Length: 3m +
Engine: tohatsu 25hp
Join Date: Jul 2010
Posts: 33
Will check fuel pump and primer bulb. I did have a look at fuel filter while on river and filter was full all the time so to my knowledge this shows the pump is ok as fuel pulled through constantly.

Damn engines.....why can't it be simple to find problems...
__________________
Commando C2 is offline   Reply With Quote
Old 26 April 2015, 13:23   #10
Member
 
1eyedjim's Avatar
 
Country: UK - England
Town: Birmingham
Boat name: Sparrowhawk
Make: Osprey
Length: 5m +
Engine: Yamaha 90hp 2T
Join Date: Apr 2010
Posts: 215
Had the same issue when I got my zapcat

Fuel pump needed rebuilding and carb adjustment screws needed removing and cleaning as was seized in

After this it runs bang on and flys
__________________

__________________
1eyedjim 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 11:48.


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