1970 650 Merc still won’t go over 3000 rpm

[Linkedit]

Thanks for all your help this far.

what I’ve done,
- remove carbs, soak clean rinse, blow out, push thin wire through small holes blow out again rebuild with new kit from mercury.
- replace any wire that was frayed or beginning to fray.
-take boat to water to set the carbs
-compression good on all cylinders

after playing withy the adjustments On the carbs couldn’t get above 3000 rpm still. Boat sure sounds better and goes straight to 3000 rpm, before it would go to 2400-2600 then slowly after adjusting trim I could max it out at just under 3000 rpm.

Should I attempt a link and sync? ( I have not touched any settings there)
Is this a trigger problem? ( does this model have a trigger)
how would I check that if needed?
I did notice a couple contacts in the distributor are quite corroded.


S/N 2874490
4cyl dual carb

 

[flyingscott]

Wnat is.good.compression? Check for spark or do a cylinder drop test.

 

[Linkedit]

115-118psi on all four.

can you just unplug the wires without wrecking the coil while it’s running? Still learning a lot about these motors. Sorry for all the ignorance. It’s been a steep learning curve.

 

[racerone]

Checked belt timing ?----Checked fuel pump diaphragms ?-----Checked plug wires on the correct distributor posts and cylinder.

 

[Linkedit]

Nope. Will check tonight and see if I find anything. I ordered fuel pump kit but I imagine it’s at customs still trying to get through.

Belt timing, what would I be looking for here? Would I just hook up timing light and idle with muffs on and see where it’s firing? Or remover the cap around flywheel and see if theres an arrow on the pulley above the distributor?

 

[Linkedit]

Well I removed the flywheel cover, turned it a few times by hand didn’t see any markings on pulley just a roll pin in top.

I hooked up a timing light rotated the fly wheel by hand this is what I got. In neutral 6.5degrees BTDC cyl. 1 fired, moved lever by hand till small plate just touched the “y” on top of carb. Rotated wheel cyl. 1 fired at 10 degrees. I moved lever till distributor maxed out. Rotated flywheel till cly. 1 fired 38degrees it fired at.

I also ran the timing light down through the firing order 1-3-2-4 and rotated the flywheel as they fired in the order correct.

Should this be checked cranking?
Was this the correct way to check?
my book says the throttle pick-up should be 7-9 degrees and timing should be 38 degrees so the last part seems correct to me.

 

[Linkedit]

So I completed a spark gap test all plugs are jumping a 7/16 gap with a good crisp audible spark.

I’m still waiting for fuel pump rebuild kit from seaway. Could be awhile getting through customs.

Is there any electrical problems that could be causing this that are worth investigating? Could it be a stator issue? I believe no trigger on this model. After I replace the fuel pump I think I’m at a dead end repairing all the things That have been suggested.

I’ll report after I get the fuel pump replaced.

A big THANK YOU to all you helpful folks on here. Lots of info to be found.