Gradual Loss of Power, Overheating

[forcenine]

Gentlemen,
The belowmentioned problem is occurring on a maiden voyage/s after months of troubleshooting and replacements to start and run the A4 on a 1979 Catalina 27. It does not happen at the dock, only underway:

After 5-10 min. underway, the power starts to slowly attentuate and then the egine dies. Simultaneously the temprature starts to rise to 200 at which time the engine completes its swan dive. This happens without touching the throttle and adding throttle does not help, nor does pulling out choke. Then engine will restart and whole process begins again.

It seems as if it is starved for fuel. The carburator has been rebuilt and the electric fuel pump is new as is the fuel line and the tank was emptied and new gas put in. In order to accomplish the engine start originally, I installed a primer bulb and must prime the carb full of gas to effect a start. A friend took the carb off after the test run with the thought that the float could be stuck (or a jet clogged) and we believe the bowl did not have much gas in it to drain. I have been told a fuel pressure guage is probably the next best step in access if the gas is getting through. it's almost like the priming puts gas into the carb bowl, the engine uses it and then runs out of gas since it is not getting enough (?) but then it does restart.

I am interested in a post I found that seemed to relate similar symptoms with the suggestion that a faulty oil pressure safety switch could be the culprit. But wouldn't the engine die quickly if it were that?

What are your best guesses, guys?

Lisa,
KNOT HIS, Cat 27

[Don Moyer]

Lisa,

I think you're correct to suspect fuel starvation. Catalina was in the habit of installing a fine brass screen mesh over the end of their pick-up tubes which of course tended to clog. Unless access is a problem on your particular boat, pick-up tubes are rather easy to remove. You simply disconnect the hose and unthread the fitting above the tube until the tube comes out.

You could also have a blown fuse in the newly installed electric fuel pump installation. It's difficult to hear the fuel pump while the engine is running unless you happen to have an automotive stethoscope (they cost around $10 at your local auto parts store). If the pump is not operating, you are relying on gravity flow which will not usually sustain for more than a few minutes.

Don

[forcenine]

Oil Pressure Safety Switch?

Don,
Do the symptoms sound at all like it could be a bad oil pressure safety switch? Will check for operating fuel pump. Think a previous inspection probably rules out fuel pick up tube. Thanks.
Lisa

[rgoff]

You can bypass the oil pressure safety switch by clipping on a wire jumper across the 2 terminals of the switch. If you don't have a jumper with "alligator clips", you can get them at Radio Shack.

I do this sometimes just to prime the fuel system (with the ignition switch ON) if I haven't used my boat in a while.

[Don Moyer]

Lisa,

Ralph's response to your oil safety switch question was right on target in terms of an easy diagnostic procedure, but I'm not sure that your symptoms are completely consistent with a defective oil pressure safety switch for the reason you mentioned, i.e., the engine would not usually get enough fuel to run for 10 to 15 minutes. But then, that rationale would apply to my suggestion of a defective fuse as well. Bottom line is that you won't know for sure until you complete the check of the fuse and the safety switch.

I'm really more perplexed over your report of a rise in temperature. Is it the case that the temperature is completely normal for the first 10 to 15 minutes (160 to 170 degrees) and then just as the engine begins to lose power the temperature begins to rise to 200? If so, the next time you're out, please try to watch the temperature gauge like a hawk to see if you can determine whether the temperature rise precedes the power loss by a split second or two, or if the temperature is normal at the first instant you detect the power loss and then slowly begins to rise. I'm having trouble relating any kind of fuel starvation scenario to your elevation in temperature.

Don

[forcenine]

Don,
After cleaning carb (again) and bypassing oil pressure safety switch and hearing fuel pump working, decided to try compression test (again). Not good, althouh it was compression tested by a mechanic before I knew as much as I now know and I was told it was OK (looking for those numbers). Now it's 100-55-72-80. Starts great, idles good with temperature fairly stable 175-190 (even after flushes andby pass restriction kit), but in gear the throttle will not power up. There is some, not lots, of blue grey smoke out exhaust. Not sure if it's more than normal.

Curious, but probably unrelated (except perhaps to the issue of under load overheating) is that I observed the shaft rotating at idle but NOT in gear. Not till I was working alone of this did I observe this happening. During a haulout, the shaft was undone to put on a cleaned up packing gland. Fiberglass mat and blow torch were necessary.

Before leaving boat this morn, I put MM fuel treatment in gas tank and ran engine for 20-30 min after putting MM fuel treatment but did not have time for new compression test. Originally this motor, sitting for years, had compression improve after flooding it with Riselone. Any thoughts? Am I doomed to pull the engine out for valves, rings, or bonfire?
Lisa