Atomic 4

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izaura

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May 28, 2012
1
Morgan 30 30 pickering
Hi to everybody.
I have trouble with Atomic 4. Engine starts, works fine. After o.5-1 hour of operation stops. If restar, work hardly with low RPM as it difficult to switch gear. Temperature 120-150C, oil pressure about 20, gas pump rebuilt, sparks are new.
 
higgs

higgs

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Aug 24, 2005
3,736
Nassau 34 Olcott, NY
Oil pressure sounds a bit low, but temp is fine. I have heard of overheating coils being a problem and causing the engine to stop. Oil pressure can be adjusted. I Can't remember what optomim is, but 20 is pretty low. I had an A4 for over ten years and even rebuilt it myself, so I know a little something.

Actually running as cool as you are causes the head to carbon up. so it is better, according to Moyer Marine to kick the revs up so you are running around 170 -180 degrees. That carbon can cause problems.
 
Rich Stidger

Rich Stidger

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Feb 10, 2004
4,235
Hunter 40.5 Warwick, RI
I had an A4 in my 1968 M30. I had similiar issues with stopping without any warning. I agree about the coil overheating- I think I put a resistor in series for running and it was jumpered out for starting. I also thought that my fuel pressure was low at 1-2#. I think it was supposed to be about 4#. The thermostat spec was 140 but I used to run a 160. The oil pressure adjustment is a spring-loaded ball bearing that lifts off the seat when the target pressure is reached. To increase the pressure simply increase the spring pressure. It is an external adjustment.

All of the above is from memory- 15 years ago. Use the info at your risk.
 
higgs

higgs

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Aug 24, 2005
3,736
Nassau 34 Olcott, NY
I hear you Rich, but 20 lbs of oil pressure is too low on any engine.
 
R

Rag Doll

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Sep 3, 2011
59
O Day O Day 28 Michigan City, In.
higgs said:
I hear you Rich, but 20 lbs of oil pressure is too low on any engine.
Click to expand
Oil Pressure is low but is the guage reading properly. I had an A4 in my 1966 Alberg 30 and it ran like a Bat out of Hell except for one period in time and it would just stop. The problem was the Points closing from vibration of the engine. The screw that set and held the Points in position was slightly stripped and the screw did not have enough torque to hold the points at the Match Cover setting. Everyone knows what a Match Cover is? Right. I went to a larger screw and it resolved the problem.

Are you starving for Gas?

Possible Coil Problem as well.

A4's are very dependable and easy to work on. The only problem for me was that it is Gasoline.
 
higgs

higgs

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Aug 24, 2005
3,736
Nassau 34 Olcott, NY
Rich - I am agreeing with you. Before one gets into a panic over the low oil pressure one must turn the screw. Do you remember where it was. I remember it being low down on the flywheel end to the right - when facing the flywheel.
 
JonnyQuest

JonnyQuest

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May 18, 2010
543
Oday 27 Gulfport, MS
A4 Oil pressure adjustment located near the carb/fuel pump area. See the highlighted adjuster on the attached image for a visual. Jump over to moyermarine.com forums for specifics on removing and cleaning the crud out of the adjuster which can give a person oil pressure reading issues.

Idle oil pressure of 20lbs is typical on A4s, and then it should ramp up to as high as 40lbs at cruising. Plenty of discussion on what is normal at moyermarine forum, with a fair bit of variety from all the users.

I'm thinking overheating coil as well.

(Disclaimer: Not my engine in the photo, mine looks a bit dirtier and has a big boat attached to it ;) )
 

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