Universal M25XP problem.

[pzmaria]

Hello all members and Catalina owners. I just became a proud owner of my first C30 and I'm quite new to the engine that is installed on this boat. It's an older model from 1987. It was never used extensively as far as I was told and engine hours were not excessive. She has a Universal M25XP. She was an a way from western Florida to Dry Tortuga National Park in Key West. Due to the weather conditions we had to use engine for about 15-20 hours. At some point the engine got hot (200-220 deg) and was shut down. Hard to tell how long it was running at this temperature as a guy at the helm didn't check the temperature gage. It was the smell of overheated engine that caught our attention. During the first investigation we noticed that there was no water coming from the stern so definitely raw water system problem was causing overheating. Raw water pump was checked, impeller checked - all good. We had no time to check the heat exchanger where I suspect is the problem - please correct me at anytime if my conclusions are wrong. Right now she is back to the dock in Florida and I had to go back to Canada. What I was able to check before leaving was exhaust pipe all the way from the stern to the wet muffler - no blockage, no obstructions. There is no water on the oil dipstick. What worries me is some traces of oil in the coolant overflow container. It is possible to start the engine but exhaust fumes are coming from air intake filter.
I'd like to hear from owners experience what I can expect when repair time comes.
Is it just a head gasket or should I be prepared for worse? I want to start gathering parts required for repair before I go back to the dock for repair. Thank so much for any input and advice.

pzmaria

 

[Benny17441]

The raw water system and the freshwater system are independent. If there is no water bubbling out of the stern where the exhaust port is, then you have a water flow problem; it could be a blocked intake clam (plastics bags, seagrass and even sea growth can block it), check the impeller and make sure the vanes are still attached to the metal bushing that spins), check hoses as soft hoses will collapse and block flow, Check-clean or replace the mixing elbow (where hot water meets exhaust combustion gases for discharge into the muffler and out the port) and yes the side of the heat exchanger that handles raw water could be blocking flow. Extreme heat breaks down oil viscosity so before anything is done an oil change is in order (20W-40). If still after an oil change you keep getting combustion fumes out of the air intake tube then you may have damaged the head gasket. Is the engine running fair or barely kept running on one cylinder? With overheating and oil breakdown there is always the possibility of stuck valves. If it were me, my plan of attack would be 1) change the oil 2) diagnose and fix any problems with the engine, 3) find and fix problems with the raw water and/or fresh water cooling systems.

 

[pzmaria]

Raw water inlet has been checked all the way to the pump. When strainer is removed raw water is flowing freely.
What about traces of oil in coolant overflow container?

 

[kloudie1]

Was the oil trace there before the overheat incident?
If you are lucky, the raw water side problem can be found and after an oil change, everything may be fine.. If a blown head gasket caused the overheat, usually a new head gasket and some careful work replacing it will solve it.. The engine is pretty tough and it would be unusual (not unheard of) for any real major problem to have been caused by a short and not too intense overheat..
Could the exhaust fumes that you smell around the air intake be the crankcase breather fumes ?

 

[pzmaria]

There was no oil in overflow container before, haven't notice any. right now is just traces on the container walls in the form of white sediment. As for the exhaust fumes it is not just the smell, they are coming from air filter like from the muffler in great quantities. Forgot to mention that when I started the engine after this whole ordeal it sounded different, something like knocking sound in gasoline engine with low octane fuel.

 

[MitchM]

#1- beware of old double wall hose going from sea water 'raw water' stainer into raw water pump. old hose can have wall separation which causes inner hose to collapse and starve pump of cooling h 2 0 at high engine RPMs. replace this hose if yours is more than 5 years old. #2/ weird smell can be due to this: after an overheat , all the hoses on engine carrying cooling raw water and 'fresh water' i.e. anti freeze could be damaged by heat and ready to blow. carry silicon hi temp repair tape and watch carefully for this. #3/ pull the ht exchanger, clean the numerous small channels thru which the cooling h 2 0 flows. 4/ install a BOREL exhaust temperature alarm, audible at the helm.

 

[Benny17441]

I was wondering about your overheat alarm buzzer. It should have warned the engine was overheating way before a damaging temperature could be reached. What was the oil level? You have not indicated how is the engine running. I gather it is just sputtering on a single cylinder with smoke coming out of the intake tube. Seems to me you may have a fouled intake valve in one of the cylinders. The cylinder head should be taken off and a valve job may be in order. Head gasket replacement will be part of it. But first I would remove the valve cover and then start the engine to see the valve train in motion and see if I spot a stuck valve. (it will be a little messy as oil will sputter all over the place). Before you do anything change the oil.

 

[pzmaria]

Just had a conversation over the phone with the mechanic. He presented the worst case scenario which would be a cracked head.

 

[kloudie1]

A cracked head is one of the things that could cause what you are seeing.. but there are a few others.. one that can be checked easily is a stuck valve or valves that do not have enough clearance.. as Benny says, the way to check is to pull the valve cover off and watch as the engine is rotated.. make sure the fuel cutoff is pulled when ya do that so it does not fire up. The mechanic should do that before pulling the head.. The raw water problem must be corrected before going much further too.