tohatsu still overheating?

slimtim · 17 July 2006, 16:02

Following on from my thread about my cooling tell tail...

Tell tail is now fine and has been for a while and engine seems to run ok (although it always needs revs to get her started, and sometimes struggles slightly at idle). However, when I flushed it out last night, the tell tail was quite hot, as was the block...hotter than I think it should be.

I checked the theromstat a couple of weeks ago and it was fine and I will check it again soon, but if that is not the problem, what else could be causing the engine to get too warm?

Why does it always need some revs to get her going (even if the engine is warm) and why does it sometimes (only very occasionally) konk out at idle?

Thanks in advance...

DM · 17 July 2006, 17:19

Sounds like the mixture's too lean. Try tweaking the mixture screw(s) a 1/4 of a turn.

DM

slimtim · 17 July 2006, 17:29

ah, interesting you mention that...I had a tweak of the screws but didn't really know what I was doing! I did suspect the mixture might be to lean but would that make it overheat?

Another question (and one I seem to have trouble finding an answer to) when I screw the screws OUT am I increasing the amount of fuel or decreasing it?

My local mechanic has told me I need to screw them right in, then out by 1.5 turns, then out 1/4 turn each until I get the best "pick up" on the throttle...trouble is I couldn't really hear any change!

Also, what should me spark plugs look like? Mine have a matt black coating, but nothing too bad...is this right or should they be cleaner? I suspect this might point to a too lean mixture?

Thanks

Tim

fast fred · 17 July 2006, 18:05

turn them in lightly till thay stop, turn out 1 1/4 turns, to 1 1/2 turns,
this will only fatten up the lowspeed circuit, but will help idle .this is not easy to do, look for a smooth idle.

to start, you need to crack the timin. when you hit the throttle Timin moves first, then the carbs come in.

brown, brown is the color you want to see. if you are lookin for a burn check
off the plugs, you can't get any thing from them if you've pulled back to the dock. you have to get the motor in the range you are checkin and pull the kill,
with out lettin off the juice. and check them on the spot.

Hightower · 17 July 2006, 19:22

Dark, sooty spark plugs seem to indicate a rich mixure already Tim. I would check out the cooling again and then get a tune up.

Incidently has your engine got an alarm for an overheating cooling system, if so is it sounding?

codprawn · 17 July 2006, 19:33

Don't worry about needing some throttle to start the engine - most do!!! I would also agree black plugs mean too rich or not a hot enough spark.

ADS · 17 July 2006, 21:50

Quote:

Originally Posted by codprawn

Don't worry about needing some throttle to start the engine - most do!!! I would also agree black plugs mean too rich or not a hot enough spark.

Cold start just choke for my 70HP Tohatsu, you can blip the throttle but it doesn't really need it.

slimtim · 17 July 2006, 23:09

ok thanks guys. Andy, I think there is an alarm, but nothing sounds.

Can anyone tell me which way I need to screw the screws to decrease the amount of fuel in the mixture? I'm guessing by fast fred's post (thanks) that I screw out to increase fuel, so I may have them too far out at the moment. Fast fred, what do you mean by the timing and how do I go about making sure its ok?

Cheers

Tim

fast fred · 18 July 2006, 11:37

in for less out for more.when the throttel cable moves, think that one pulls,
on some Carbs crack open, next thing that needs to happen , full timeing needs to kick in, by full i mean what ever factory says for that motor, 20-22deg max, usally done with a low spot on the trottle cam.
if you havent messed with it it's prob ok.

Scary Des · 18 July 2006, 11:58

Tim if you aren’t sure where the carb screws are it is probably best to start again, screw them fully in and do as your local mechanic suggests. With a bit of playing you will begin to get a feel for what is right andyou are unlikely to do any damage.

With regard over heating, engines do get hot but it is quite difficult to gauge how hot, I would suggest getting a multi meter with a temp probe so you can get a better feel for how hot your engine is. I have one you could borrow if you fancy a trip up the Beaulieu

Des

Hightower · 18 July 2006, 13:00

What is the normal operating temp for an outboard....Same as car? Or lower as it's an unpressurised system?

slimtim · 18 July 2006, 13:20

Quote:

Originally Posted by fast fred

in for less out for more.when the throttel cable moves, think that one pulls,
on some Carbs crack open, next thing that needs to happen , full timeing needs to kick in, by full i mean what ever factory says for that motor, 20-22deg max, usally done with a low spot on the trottle cam.
if you havent messed with it it's prob ok.

Fred, thanks although not entirely sure I understand all of it

! The only things I have tweaked are the mixture screws, the idle screw and the throttle stop screw as this was adjusted so that the carbs won't opening fully...I now have an extra 200rpm at WOT

I'll screw the mixture screws back to 1.5ish turns out, and clean the spark plugs (whats the best way to do this?).

Scary, sounds like a plan, thanks. I'll see what effect adjusting the screws has.

Any more help appreciated.

Tim

slimtim · 18 July 2006, 14:38

http://www.motocross.com/motoprof/mo...lug2/plug2.htm

just found this. Bit confused now. Need to check my plugs again and take some photos.

Lean = too much air = overheating but then my plugs are (i think) lightly sooted pointing towards to rich a mixture!

Scary Des · 18 July 2006, 15:30

Tim I would be inclined to get a new plug so you are starting from a known point, your plug could be old, oily etc. Also I would run it under load and then look, it surprising how quickly some plugs look sooty when the engine have been idling for a bit.

Des

Jizm · 18 July 2006, 16:28

Tim, don't want to teach you to suck eggs but do you have water coming from under the cowling (thermostat outlet on pic) when the engine has been running for a minute or so?
Also if the engine has been stood for a while it's definitely worth stripping the carbs and then putting them back to the base settings as your mehanic mentioned.
Have you got a service manual? shouldn't have too much trouble getting one for your motor as it is relatively young, and they are invaluable.
hope this helps

Jizm · 18 July 2006, 16:32

Quote:

Originally Posted by Hightower

What is the normal operating temp for an outboard....Same as car? Or lower as it's an unpressurised system?

I think it's a bit lower as I can put my hand (without scalding myself) in the water when testing if the thermostat's opening in a saucepan. Also they open up pretty quick when the motor is left to idle.

slimtim · 18 July 2006, 16:54

aha, so that outlet should only have water coming out of it when the thermo stat is open and letting water flow down the cylinder head (i.e. when it has reached optimum running temp and needs to open to regulate it and keep it close to that temp)? I didn't realise that outlet was purely for the thermostat! I will check it tonight.

I need to get me one of those manuals too, just haven't got round to it. May get mr mechanic to have a look tomorrow.

Thanks Jizm.

Jizm · 18 July 2006, 17:32

Yep, the impellor pumps the water up the leg and around the cylinder head, when the water gets hot enough to open the stat, water comes from the outlet under the cowling, doesnt take long. When the stat opens it not only lets the hot water out of the motor, it replaces it with fresh sea water, so the stat will probably partially open and remain that way to maintain operating temperature.

Jizm · 18 July 2006, 17:35

Tim, have a look at the link below
here

Jizm · 18 July 2006, 17:36

This one may be better

here