Yamaha 3HP Malta

Took dinghy out over weekend and starts much easier but now I think Idle a little too rich so mix screw half turn in. Still a bit sluggish in gear. If I had to guess probably reaching 3000rpm at 100% in gear not sure if this is capable of reaching max rpm limit. Should it be???

Replaced carburettor gasket today along with propeller and anode. (Prop looked like 1995 original and a little worn)
 
gordmac said:
Strange, don't recall any connection between the gears and throttle. The butterfly opens fully in neutral but not in gear? That could be the issue.
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The butterfly opens fully in both neutral and in gear but I don't seem to be able at present to reach full power in gear.

Tom
 
I tried this eve to remove the carb bowl drain screw but just snapped the head off it. No fuel came out buy temporarily put a blob of silicone sealant over it just in case

Anyone know if it's possible to get a replacement screw? or what thread it is?

Also I found a pipe disconnected that runs from the top of the engine (below fuel tank) to the bottom (adjacent to tiller arm pivot where it was dicsonnected), I have re-attached it but would like to know what it does? possible breather pipe?
 
Honda Z50M said:
I tried this eve to remove the carb bowl drain screw but just snapped the head off it. No fuel came out buy temporarily put a blob of silicone sealant over it just in case

Anyone know if it's possible to get a replacement screw? or what thread it is?

Also I found a pipe disconnected that runs from the top of the engine (below fuel tank) to the bottom (adjacent to tiller arm pivot where it was dicsonnected), I have re-attached it but would like to know what it does? possible breather pipe?
Click to expand...

I think the little fitting on the top of the engine exits insids the cylinder bore, so I assume they are using the pressure/vacuum for something?
 
Just looked and it appears the top pipe is drilled into the cyl bore, and the rubber hose carries it down to the main bearing.
This hole

Screen Shot 2020-07-30 at 14.16.17.png

To this nipple
Screen Shot 2020-07-30 at 14.16.25.png

Then through hose to feed bearing , of course it could also be working the other way!
Screen Shot 2020-07-30 at 14.16.43.png
 
If that was disconnected it could be drawing air into the crankcase, sorting that may solve your problem. No idea what it does though!
Edit: I wonder if it takes oil/fuel to help lubricate the piston and bore?
 
Yes that's the puppy THANKS!

It will explain why revs run away slightly.

Hopefully I'll get a chance to run it up tomorrow.

Would still like to know its job?
 
Fitted an iridium spark plug and ran it and at first would not idle at all, eventually ran it full throttle and backed it off a few times and that must of cleared the idle jet as now ok.

Seems to rev up a fair bit faster and when in gear seemed to rev up almost as fast. So looking good thus far.

Will have to try it in the real world on the river to see.
 
Went out on the river today, small improvement but not as much as expected.

Now turning throttle on tiller, when I reach 60% that's about max revs, no change from 60% to 100% throttle?
 
Honda Z50M said:
Went out on the river today, small improvement but not as much as expected.

Now turning throttle on tiller, when I reach 60% that's about max revs, no change from 60% to 100% throttle?
Click to expand...
Is the engine to deep in the water? The transom on my dinghy is quite low and I have a lock of wood to raise the engine up. This made starting easier and the engine i seem to remember reved better.
 
Even in perfect condition a Yamaha 3HP Malta (6L5 would behave a little sluggish (pushing 3.2M dinghy with 2 adults and 2 children).
Try a larger engine.
 
I don't see how the engine being a little deeper in the water would account for 40% power and te Malta apears to have an exhaust bypass to elleviate back pressure.

May be I am expecting too much from a little engine although 95% of the time throttle is at start position or less just pootling along the river.

Tom
 
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