tower of power loss power

[cuenta619]

The motor dies when put gear
And when run only go at 4400 rpm but in neutral 5500 rpm
The motor is hard to start and only keep fire if squeeze the prime buld
The problem began after of ajust throttle cable and clean bottom carb.
Any idea .
1978 140 hp?

 

[Chris1956]

Gee, A lot of issues come to mind. Did it ever reach 5500 with the current prop?

If she won't run without squeezing the primer, you likely have a fuel pump problem.

Your adjustment of throttle and carb may/may not be relevant. There is no way to tell with the info given.

 

[cuenta619]

I forget to mention that I change the propeller by a 21 pitch stainless steel before had 17 pitch aluminum looking for a little more speed.
How many rpm normally drop a bigger propeller to a motor like this

 

[Chris1956]

Going from a 17P prop to a 21 P prop would cause a RPM drop of about 800. That kind of drop could cause you not to be able to plane, as the motor is out of it's powerband.

What kind of boat are you running?

 

[cuenta619]

1980 Glastron 16.2 ft.
900 lbs.
Max. Top speed 50 mph

800 rpm is a lot of drop
Maybe I back to old prop.

 

[Faztbullet]

Something's wrong with the motor as it should easily turn a 21 on that boat, if it ran with a 17 I suspect motor is worn/compression low.

 

[Chris1956]

I agree with Fazt. Check for spark plug wire arcing to ground and water intrusion, after compression check.

 

[cuenta619]

I will check the compression !!!!
The last time I check had 120 psi.in all cylinders
How many psi is the good range to this mercury

 

[Chris1956]

120PSI is good, however, compression gauges are not real accurate. So if all the cylinders are within 10% of each other, the compression is good.

 

[cuenta619]

No Title

Try to ajust the adle speed I noticed that the throttle stop screw is missing.
Have this any effect to start the engine ??
I take this pic. Of other post to reference

 

[Chris1956]

The Throttle stop screw stops the operator from over opening the carbs, and damaging them. Check your carbs for damage on the butterflys and replace the throttle stop screw. It should be a standard 5/16" stainless screw.

 

[cuenta619]

And the spark advanced was all way out
Any instructions to sincronisation those

 

[Chris1956]

Sure, Max Spark advance should be 21* BTDC. So remove spark plugs 2-6 and install them into their wires and ground their bases. Set the throttle to full, install a timing light onto #1 spark plug wire and jumper the starter (ign on) to crank the motor. The timing light should read 21*BTDC. Adjust max spark advance screw until it does.

You can use the same set up to set the idle pickup timing. Advance the throttle until the carbs are just ready to open. Check the timing. It should be 4-6* BTDC. If the timing needs to be adjusted, loosen the two stainless hex screws on the brass collar on the distributor, and rotate it and adjust the throttle until the carbs are ready to open and the iming is 4-6* BTDC. Tighten the bolts.

 

[cuenta619]

Sure, Max Spark advance should be 21* BTDC. So remove spark plugs 2-6 and install them into their wires and ground their bases. Set the throttle to full, install a timing light onto #1 spark plug wire and jumper the starter (ign on) to crank the motor. The timing light should read 21*BTDC. Adjust max spark advance screw until it does.

You can use the same set up to set the idle pickup timing. Advance the throttle until the carbs are just ready to open. Check the timing. It should be 4-6* BTDC. If the timing needs to be adjusted, loosen the two stainless hex screws on the brass collar on the distributor, and rotate it and adjust the throttle until the carbs are ready to open and the iming is 4-6* BTDC. Tighten the bolts.

There is another method without using the timming light?
I not have help to jump the starter relay and Look the timing light

 

[DVTO2]

If you to squeeze the prime bulb to get it to run it sounds like a fuel problem to me.

 

[Chris1956]

Gee, get a piece of wire with two alligator clips on it, and use it to jumper the starter solenoid. So attach the jumper with left hand, and point and read timing light with right hand + eyes.

 

[cuenta619]

Gee, get a piece of wire with two alligator clips on it, and use it to jumper the starter solenoid. So attach the jumper with left hand, and point and read timing light with right hand + eyes.

Good trick

 

[cuenta619]

Yesterday test the boat and top speed was 47 mph.
With 17 p propeller.
Today switch to 21 p propeller and test again the motor only go at 2k rpm return to home I check the compression and all 6 cylinder have 125 psi
Any idea what happen with this propeller is to much to this motor or need ajust something to run with this prop..

 

[Chris1956]

What you are seeing is normal when the pitch of the prop is too much. The motor cannot spin fast enough to develop enough power to accelerate (unscientific description).
I would recommend a 19P prop to test.

 

[cuenta619]

I'll try again with the old propeller and see what happens.
I buy new one because the old has some dents
But the motor can't with it