Tohatsu M70A2 fuel problem and coolant leak

[kaferhaus]

Hoping Tohatsu Guru or someone else will chime in here...

bottom cyl is starving for fuel at all rpms.... squirt gas into that carb and dramatic rpm increase. Squirt gas in top carb very little change. Turn air screw in on top carb, engine quits.... do the same on the bottom carb, no change.

The reason I haven't immediately torn into the bottom carb is this... I have a inline clear glass fuel filter. Pump this full of fuel from the primer, start the engine and once it starts the fuel level in the filter drops very very low and no matter the rpm there's barely fuel in the filter... pumping the primer bulb does of course keep it filled BUT makes no change in how the engine is running. I do notice that where the fuel line meets a "T" between the carbs it's a little shorter from the "T" to the top carb than the lower.... could it be the fuel pump weak and just not supplying enough fuel to feed both carbs? Or is this "normal"....


Second issue is on the left side of the engine towards the rear there's some sort of plastic elbow that feeds the tell tale... this elbow is cracked and of course a steady jet of water is spraying out of it... plenty coming out of the teltale but obviously this is leaking water onto the engine.. is there a replacement part for this? Maybe I just missed it but I don't see one on the parts book...

 

[TOHATSU GURU]

Re: Tohatsu M70A2 fuel problem and coolant leak

"could it be the fuel pump weak and just not supplying enough fuel to feed both carbs?"

Yes, it could be a bad diaphragm(s) in the fuel pump....Or:

Low compression
Broken reeds
Carburetor issue
General fuel system issue(air leak)

"Or is this "normal"...."

Its a beauty is in the eye of the beholder thing. The degree to which a filter empties or retains fuel can vary and still be considered normal, so, without seeing it myself, I would say its probably okay....Maybe....Sort of.


Download a parts book from http://www.internetoutboards.com/PartsCatalogMenu.htm and then look at figure 16, item 18. Is that the part you need?

 

[kaferhaus]

Re: Tohatsu M70A2 fuel problem and coolant leak

compression is 150 on both cylinders,
no cracked hoses no apparent vacuum leaks Used propane gas around gaskets and vacuum lines.

Guess I'll take the airbox off and hold my hand over the bottom carb to make sure it's pulling air to check the reed valves.... I'd assume that that is a very very rare occurance... baring that I'll pull the bottom carb... this engine looks new under the cowling but I guess it's possible that the bottom carb is not supplying any fuel at all.... never seen it except on a engine that was set up for years.... usually either the low speed circuit is plugged or the high speed circuit has trash in it....

The tell tale part I need is at the other end of the tell tale hose... not in the lower cover, it is on the engine.

 

[TOHATSU GURU]

Re: Tohatsu M70A2 fuel problem and coolant leak

Download a parts book from http://www.internetoutboards.com/PartsCatalogMenu.htm and then look at figure 16, item 18. Is that the part you need?

 

[kaferhaus]

Re: Tohatsu M70A2 fuel problem and coolant leak

Okay, the bottom carb had a stuck float.... the previous owner had re-assembled the carb incorrectly and had left the float hinge pin protruding too far to one side which was putting the float in a bind. Carb looked spotless other than that.

So now both cylinders are firing but I cannot get a "smooth" idle the engine shakes a bit at idle.... is this "normal" for these big 2 cyl motors? If not then I have to assume there's a little trash in the low speed circuit on one or both of the carbs.

The water leak at the tell tale elbow on the block.... apparently that's a non-replaceable part..... Tohatsu dealer told me to either JB weld it or break it off, tap the hole and screw a brass elbow into it..... I'll try the JB first but don't know how well it's gonna stick to plastic...

 

[TOHATSU GURU]

Re: Tohatsu M70A2 fuel problem and coolant leak

It should run fairy smooth, but that's a relative term. If is is jerking it has an issue. If it is just "rough" that would be considered normal for a big bore 2-cylinder.

That sounds like the nipple on the side plate....Part number 353011370M and they are around $3.00 or $4.00.