M70A - No power/low RPMs

[FONT=&quot]Hello-[/FONT]

[FONT=&quot]I recently acquired a Tohatsu M70A from my father and Im having some issues with it. The thread below seems to describes the same issue I'm having:[/FONT]

http://www.marineengine.com/boat-fo...0-Tohatsu-no-rpms-and-no-power&highlight=m70a

[FONT=&quot]Starts great, Idles great, in neutral open the throttle up (either through the warmup lever or manually at the engine) and she screams RPMs and runs great. Runs fine in reverse. When you shift it into forward it runs fine, but when you get to anything more than 0 degrees, it _sounds_ like its going to try to get going, but then the RPMs suddenly drop. It used to stall at that point, but now the RPMs just drop off. I get going to about 5MPH at wide open throttle. She just doesnt wanna get up and go when under load. [/FONT]

[FONT=&quot]What I've done:[/FONT]

• Sprayed carb cleaner in both carbs and run through twice
• Replaced the fuel line and bulb from tank to motor
• Replaced fuel lines from filter all the way to the carbs
• Replaced fuel pump
• Checked compression: 120PSI on three cranks for both cylinders (150PSI on 5 cranks for both, and that's where it tops out)
• Checked ignition: spark at 10mm gap with inline tester
• Plugs are a little oily but the insulator tip is whiteish/tan, they look good

[FONT=&quot]The thread above talked about checking the reed valves, which I have not done yet. Can I take the carbs and reed valves off the motor without having replacement gaskets, and put it back together effectively? Also, Ive seen plenty of posts across the internets stating that the carb rebuild kits are nowhere to be found. Do I really need a rebuild kit, I figure i only need a new float bowl o-ring if I pull that apart to inspect the jets. I can get a new o-ring from the ebays.[/FONT]

[FONT=&quot]Anything else I can be looking into?[/FONT]

Spraying the carbs makes them shiny; It doesn't clean them.
Probably need to do a proper cleaning.
Reeds seldom are an issue.

Thanks sir, I'll have a go at that.

Double posted by accident

Ok I pulled the carbs apart and both slow jets were pretty well gummed up. Cleaned everything with a nylon brush and all the crud is gone. I noticed the float in the top carburator is a fair bit higher when they both sit upside down on the table. Check the attached image. How/should I adjust these? I don't imagine i want the gas at that level when the float valve closes? PM'd you @pvanv about a service manual too.

Evidently the pictures didn't attach.

They should be about parallel to the casting when inverted.

Welp. I replaced the floats, float valve and pins, cleaned out all the garbage and slapped it all back together and.... Now it doesn't start. Sigh.

It'll spin and pop once sometimes, but mostly it just keeps cranking. Any ideas what to try now?

Check whether you have a wet or dry plug(s). Wet=no spark; dry=no fuel.

So I ended up getting it started, but it sounded pretty rough on idle. Pretty regular 'louder' pop sound with some smoke, and the engine shakes a touch. I used the shop manual to set the timing linkage to factory specs, which I was mostly able to do. The only bits that i couldn't seem to get to factory were the two stop screws. Setting those to factory of 20 and 23 mm made them miss the stops on the advancer arm so that they were coming down on top of the stop screw threads rather than against the end of it. Having said that however, at full closed throttle the mark on the flywheel lines up with the TDC mark on the magneto(?) and full open lines up with 22.5 BTDC. I also changed the plugs with new NGK BH8S-10 and while that 'seemed' to improve things a touch, still sounds kinda rough. It's idling in the mid 900RPMs and it i try to adjust the throttle stop screw any lower it will stall. Running it up to 2000RPM it sounds like it smoothes out a touch, but definitely still rough. Is that poppin a misfire or backfire? Any idea what might be next to diagnose? Can/should i put it in the water and see how it runs under load?

Sounds/looks like this:

https://youtu.be/kZ70nO9-5nA

That idle speed is OK, but something is wrong if you can't use the stops for timing limiters.

I got it out in the water yesterday and the power loss/low RPMs under load is no longer an issue, this thing moves. It still sounds rough at lower RPMs, but sounded pretty smooth up at high speed. I didn't open it all the way up, the bay is a little unpredictable with respect to chop and there was a few points where we left the water entirely lol.

The stops hit nicely on the advancer arm at the m55 specs of 10 and 15mm respectively. Do you think perhaps the guy that worked on it a few years back replaced or installed the wrong advancer arm? Are they different parts for the m55 vs the m70 that I have?

Hard to say, since the parts catalog for the 55B is NLA. Anything is possible.