Engine shutting down gently, possibly cooling problems

[Bobncae]

We purchased our Catalina 30 with the Atomic 4 engine a few months ago. Recently, after about 1-2 hours she shut down gently. WE can get her to start back up sometimes. She is a raw water cooled and also has a fresh water cooling system as well. The water hoses are very hot to the touch.We've replaced the electric fuel pump (today) as well as the raw water pump. We are still experiencing problems with her running hot. It appears that some steam is coming out of water hose leading to the radiator. When we first bought her, we had the carborator rebuilt as well as the starter solenoid, new starter, etc.

recently, a mechanic came down to look at it and charged us $200 to change our fuel filter and "clear" a clog out of our fuel vent.

Should we replace the thermostat? Any advice would be appreciated.

Thanks
Cae

[Don Moyer]

The remedial actions performed by your local mechanic were right on target and have the potential of correcting your intermittent shutdown problem.

Catalina 30's are a bit more prone to fuel supply issues than other boats due to the longer than normal distance to their fuel tank and the fact that the tank is slightly lower than the engine. For this reason, we recommend that a fuel pump be used with at least 4 psi.

If the shut downs continue, you might also check for a clogged screen at the end of the pickup tube in the fuel tank and/or a second factory installed filter under the aft berth to the right of the tank.

Regarding your overheating problem, it would help to know that temperature the engine is reaching. It's normal for fresh water cooled engines to operate slightly hotter than raw water cooled engines (180 to 190 degrees). I'm not sure about replacing the thermostat, but I'd at least remove it for cleaning and checking. If the thermostat is a 180 degree model (as shown on the bottom of the brass heating element), I'd replace it with a 140 degree thermostat.

Don

[Bobncae]

Followup-Cracked engine block?

We took off the thermostat housing to check for corrosion or blockage. Beneath the thermostat we found what appeared to be metal sludge. We picked up probably a tablespoon of it from the coolant using a magnet. We took the thermostat and housing to a local marine parts supplier with the intention of purchasing a 140 degree thermostat as you recommended and get their opinion. The guy we spoke with, who has always been very knowledgeable, said he thought we had oil in our thermostat housing and possibly the coolant which lead him to believe we have a cracked engine block.

The engine has been running at approximately 200 + degrees we think. Our guage is faulty too, so it is difficult to be sure. The underside of the thermostat housing did have some black residue, but we have been using a corrosion eating spray. Based on what we read in the Moyer Marine Manual, it didn't look like the thermostat housing was shot, but we couldn't figure out what could be causing the metallic sludge in the bottom.

We are probably going to call someone tomorrow to run a hydrocarbon test to ascertain whether or not there is oil in the coolant, but were wondering if anyone else has had problems along these lines and might know what else we could try.

[Don Moyer]

Bobncae,

I believe I can relieve your concern in one area. There are no oil passages in the Atomic 4 block that run close to a water jacket, so we have no history of oil from the crankcase finding its way into the engine coolant through a crack in the casting.

Don