Over propped?

[rickinnj]

Forgot to mention, I bypassed the in-line fuel filter prior to the previous tests. I replaced it this spring but wanted to eliminate it a source of fuel starvation.

[joe_db]

Under load:

Forward full throttle is 980rpm and steady 2 inHg .
Astern full throttle is 1125 rpm and a steady 2inHg.

That looks like a very overpropped engine or there is some other source of drag somewhere.
At 2" I would get over 2,000 RPM unless the prop is badly fouled.
Also, you may want a snubber for the vacuum gauge so it doesn't jump around.

[rickinnj]

Confirmed firing order. Changed cap and rotor…cap terminals were burnt and pitted.

In idle vacuum smoothed out considerably at 15”Hg.

Full throttle in forward still 980 but vacuum improved to 3”Hg.

Vacuum drops to 13”Hg at 2500rpm

Progress!

[rickinnj]

With engine warmed up compression in all four cylinders is 120-125 psig.

Plugs are dry and sooty. Confirmed gap at .035”.

[rickinnj]

I clamped a spark plug to the lifting bracket and tested spark from all four wires. Strong blue/white spark.

[rickinnj]

!!!!!!!!!!!!!!!!!!!BRAND NEW DEVELOPMENT!!!!!!!!!!!!!!!!!!!!!

After I put the ignition system back together I started the motor and ran her in gear at full throttle. Same top shaft speed of 980rpm.

All of a sudden, she sped up so much that I thought it popped out of gear (I didn’t have time to get a shaft speed but I was moving water out from under the back of the boat…the prop was spinning). About 5 seconds later it bogged down again. I checked shaft speed and she was turning 1000-1150rpm.

Something is definitely binding. What’s next?

[rickinnj]

I tightened the alternator belt…it was loose and smoking. Started the engine back up and ran it forward and reverse. 1250rpm forward and reverse 1”Hg vacuum

[rickinnj]

I’m gonna loosen the shaft packing again and cycle between forward and reverse for awhile and see if that makes a difference.

[JOHN COOKSON]

!!!!!!!!!!!!!!!!!!!BRAND NEW DEVELOPMENT!!!!!!!!!!!!!!!!!!!!!
All of a sudden, she sped up so much that I thought it popped out of gear (I didn’t have time to get a shaft speed but I was moving water out from under the back of the boat…the prop was spinning). About 5 seconds later it bogged down again. I checked shaft speed and she was turning 1000-1150rpm.
Something is definitely binding. What’s next?

Sticky valve? Try running the engine for an hour at cruise RPM.

ex TRUE GRIT

[rickinnj]

Loosened the shaft packing. Cycled between forward and reverse about ten times. Achieved 1330 rpm in forward with 2”Hg manifold vacuum in forward.

[joe_db]

How easy is the shaft to turn by hand in neutral?

[rickinnj]

Very easy .

[Dave Neptune]

Rick, when she revved up and was moving water was there a difference in sound?
Sooty plugs can be caused by an over rich load situation or back pressure in the exhaust. First how old is the exhaust? And the last time it was replaced was the exhaust hose replaced? The hose can collapse on the inside causing a restriction and pop open occasionally with an increase in performance while open. Did you run the engine with the exhaust unhooked under load?
I doubt it is the carb as you changed the jet and should of noticed any debris in the bowl.

Dave Neptune

[rickinnj]

Last week during troubleshooting I pulled the exhaust off of the manifold and ran it. No change in performance.

I took the boat for a spin this afternoon I achieved 4.7 kts SOG both directions along the fairway in the marina. 1250rpm.

Then I went for a sail 15-20out of the NE with 25 gusts.

[JOHN COOKSON]

What is the drip rate after you loosened the packing nut? Or do you have some sort of dripless packing?

ex TRUE GRIT