Tohatsu oil consumption

M

mattsaks

Petty Officer 2nd Class
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Aug 7, 2004
Messages
156
Just wondering how much oil a m90a two stroke should use per 20 litres of fuel. It gets varied rpm running so I know it wont be a solid figure but just wanted an idea if the oil pump is working properly or not. It has oil injection in the fuel line before the carb. So far it has used approx 450ml of oil and 35ish litres of fuel. As this is less than 50 to 1 I wondered if it could be a little low. Any thoughts would be appreciated
 
TOHATSU GURU

TOHATSU GURU

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Jul 22, 2004
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Re: Tohatsu oil consumption

No way to tell. Varying the RPM will throw off any measurement.
 
M

mattsaks

Petty Officer 2nd Class
Joined
Aug 7, 2004
Messages
156
Re: Tohatsu oil consumption

Thanks Elvin. I figured it would be hard to tell with the variable pump. Is there an accepted method of working this out? I have been running premix in the tank as well for about 15 hours after having the pump off. It is definately getting too much oil as it gets a bit lumpy(fouled plugs) at low revs so I want to stop adding oil to the fuel but need to be able to trust the pump.
 
TOHATSU GURU

TOHATSU GURU

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Re: Tohatsu oil consumption

There is a factory spec for oil flow from the pump at one RPM setting. Tohatsu had to research this one. At 1500 RPM, the pump should produce between 33 and 40 during a 10 minute period.
 
M

mattsaks

Petty Officer 2nd Class
Joined
Aug 7, 2004
Messages
156
Re: Tohatsu oil consumption

With the pump set to full throttle, it makes 40 mls in ten minutes. On closed it makes 10 mls. Does this sound about right?
 
TOHATSU GURU

TOHATSU GURU

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Re: Tohatsu oil consumption

Your beginning to worry me. Are you talking about the setting on the pump or are you talking about the throttle of the engine being set to wide open?
 
M

mattsaks

Petty Officer 2nd Class
Joined
Aug 7, 2004
Messages
156
Re: Tohatsu oil consumption

Na just the setting on the pump. I disconnected it from the throttle linkage to see the change in volume at idle. For the original test when it used 10mls of oil, it used 660mls of petrol. So 66:1 mixture at idle. Is this about right? I am sure I have over analysed this now!
 
TOHATSU GURU

TOHATSU GURU

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Jul 22, 2004
Messages
6,164
Re: Tohatsu oil consumption

Your over thinking it. :) 66:1 is on the rich side. It should be closer to 75:1. However, there is a huge slop factor in this and that is not much of a difference. Live with it and enjoy your boat.
 
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grandepiacere

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Aug 31, 2008
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Re: Tohatsu oil consumption

Hi Tohatsu Guru,

Hoping you can shine some light on a problem I have. My 2001 115 HP (model M115A2 3J6) two stroke Tohatsu seems to be consuming too much oil and running rough as a result. Oil deposits are visible on new plugs even after a few minutes of running.

Compression is 135psi across all four cylinders. I hooked up an external tank to the engine with pre-mix gas, disconnected the oil line from the fuel pump and measured the output of oil at 1500 RPM. The result was 6ml in 4 minutes. This would be equivalent to 22.5 ml in 15 minutes. Is this normal? Do you have any numbers for this engine?

Engine seems to be running rough in general. Carbs are clean, no stuck floats or needles. The idle mixture screw is set at about 1 and 1/2 turns on each carb. Oil deposits are even on all plugs. Exhaust smells fuel rich, but if I cut back on idle mix adjustments engine runs rougher.

The only adjustment to the oil pump operation appears to be via the linkage to the throttle arm. If I were to tighten this linkage I think it would have the effect of reducing the oil consumption as designers intended at higher RPMS.

Comments from others appreciated.

Thanks.
 
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