A Tale of Two Problems...
 

Hello there!

Issue: In neutral and in Reverse I get normal rev and oil pressure, just not in forward gear.

New Plugs
New Ignition Coil
Compression Test after about 10min running (95 - 96 - 95 - 100)
New Racor Fuel Filter
Oil Change
New Carb (installing now)
Checked Exhaust Aft from Engine

The Throttle Lever on the new Carb is oriented differently than the one the old carb. With my cable configuration (Coming to engine from aft - no u-turn) The cables are not oriented to push throttle open and pull closed.

The old carb has a Throttle Arm which was oriented differently supporting the normal functioning of my throttle cable.

Questions:

1.) Any other things you would look at regarding the power issue in Forward Gear?
2.) Can I use the old throttle arm from original and new plate and screws? (it seems to fit the same and solves the issue)
3.) Is there a way to invert the throttle arm which came with the new Zenith. I can't find a way to flip it.

prop clean?
 

How's your prop?

A Tale of Two Problems
 

On my Ericson 32, I used the arm from my old carb. it was easy and quick. Mr. Moyer had suggested looking at that solution and it worked. I think the original arm was modified by Ericson, when the boat was built to avoid a long cable.

Gonna have a driver check it out. Was clean two weeks ago on the run up to Santa Barbara from Oxnard though.

Now that we know you're in Southern California, our hard growth is not that aggressive so I'm doubting a prop issue. When you said you "checked exhaust aft from engine", exactly how did you check it? I'd like to be sure there is no exhaust obstruction.

Then another thought: when was the centrifugal advance serviced?

Hey thank you for the responses! So... I checked fittings for leaks and ran the line with my hands all the way aft to where it exits the transom. No obvious restrictions or leaks. I understand that the can collapse internally but I believe it is newer anyhow. Water flow and pressure seems unchanged from before this problem arose.

I have not, nor do I know when the advance was serviced. It has electronic ignition. Not sure that matters?

I am just baffled. Everything seems totally normal except when under load in forward it only wants to rev so far before bogging and holding steady at like 25-30psi Oil Pressure. Oil PSI is 40 in normal sounding idle and astern.

New carb is going on tomorrow night when I finish work. I'll see if I rattled some gunk in there when changing the very old water separator.

Also got new fuel line with new inline filter which will go on with carb.

Fingers crossed.

Welcome to the forum! :D

Are you CERTAIN that your plug wires are in the correct order?

Thanks guys. Plugs are all aligned properly. New carb installed. Engine sounds and starts great just not getting proper oil pressure under load in forward gear still. Only about 25psi. Normal pressure when starting. Idling. In reverse gear. Just can't seem to get back to 40 at cruising speed. Not sure what to do next.

Why are you worried about the oil pressure? 25 is just fine and the pressure has nothing to do with what gear your in. RPM's, wear and heat are contributing factors for oil pressure as well type and viscosity of the oil My beastie ran for over 34 years at about 25 psi.

Dave Neptune

Thank you Dave. I guess I am just perplexed as to why the sudden change. Prior to replacing old separator for Racor and new RJ12C's it would hold 40 at cruising speed.

Made those changes and it just started behaving differently. Then with all of the other changes it had not addressed the sudden change in Oil Pressure under load.

Advance is completely independent of electronic ignition. It is composed of a pair of weights and springs located under the plate inside the distributor. The way it works is that the shaft spins, the weights swing outwards, causing the rotor shaft to rotate an additional amount in the advance direction. A quick way to check is to grab the rotor and try to lightly rotate it by hand. It should move a small amount smoothly in one direction, and the springs should smoothly return it when gently released.


Rule of thumb for minimum oil pressure is 1 PSI per 100 rpm. What RPM is your "cruise speed"? Unless you've got a 2:1 reduction, I'm guessing its not 2500 RPM. So 25 PSI is not a problem.

Still, its a change from what you were seeing before. Problems that only manifest in fwd and not in idle or reverse tend to suggest a problem in the adjustment of the reversing gear. If the reverse band does not fully disengage, it will put a large load on the engine when put in fwd. A vacuum gauge would help detect how hard the engine is working: High vacuum = loafing, low vacuum = working hard. With the engine stopped, and the shifter positioned where you think neutral is, the shaft should be loose enough to turn by hand.

Wiring??
 

Try checking the gage connections if an electric gage. I always mounted a "static" gage on a tee with the electric sender. If the cockpit gage dropped or changed I could confirm by a quick check of the static gage.

Oil pressure is controlled by RPM, heat, oil quality, engine wear and oil pump wear. And not much else!

Dave Neptune :cool:

Dumb Question Perhaps......
 

Have you tried adjusting the oil pressure? If you have tried adjusting the oil pressure did it result in a pressure change?

TRUE GRIT

I still think the lowered oil pressure is a symptom, not a cause. Its the natural result of running at a lower RPM. In post #6, the OP says:

The difference between fwd and neutral or reverse seems to be the defining symptom, which to me suggests the reversing gear. A fouled prop would affect both fwd and reverse, but not neutral. A problem in the oil pump system would affect all three.

I recall some posts here in another thread some time ago about the retaining clip on the adjusting nut on the reverse band being broken or missing, allowing the nut adjustment to change.

It would be really informative to have RPM and oil pressure measurements in the following combinations:

Throttle at idle, shifter in fwd, neutral, reverse

Throttle at cruise setting, shifter in fwd, neutral, reverse.