Was on a survey and sea trial on a 1994 hunter 30 and the overheat alarm went off. Ultimatly blew a water hose. Mechanic said the riser elbow was blocked and will be replaced. Any advice on what to look for after it is repaired? How to tell if any serious damaged occured in the 15-20 min period engine ran- slowly but not idle the last five min before shut down- by the owner-- was with the separated water hose. The alarm is an idiot light not a temperature guage. Is installing on a big deal--or can a saturday mechainc do it? Thanks
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The thermostat might be worth replacing at the...
same time. An oil change is also advisable. The engine should survive the experience not much worse for wear. A methodical "Saturday" mechanic should be able to do anything on a simple diesel engine that a "real" mechanic can do...
same time. An oil change is also advisable. The engine should survive the experience not much worse for wear. A methodical "Saturday" mechanic should be able to do anything on a simple diesel engine that a "real" mechanic can do...
Look in the archives for guage installations.
Fred: There have been several threads about gauges in the past several months. Even if you decide to install a water temp gauge do not disable the buzzer. This is not like a car with the instrument panel right in front of your face. You need have this buzzer to warn you ahead of time. There is no telling how hot the engine got, but I must assume that there was still some water running thru the engine. Plus this is a fresh water cooled unit so you still had some cooling. If it got hot enough to do damage the mechanic that is changing out the elbow should be able to tell you. Just for the heck of it, ask the owner what RPM range he normally ran the engine at. Probably always ran the engine at 2200 or so RPM's. Also, make sure that they are putting on a new mixing elbow and not just cleaning the old one out. If the old one is not rusted thru you can clean it up and use it for a backup.
Fred: There have been several threads about gauges in the past several months. Even if you decide to install a water temp gauge do not disable the buzzer. This is not like a car with the instrument panel right in front of your face. You need have this buzzer to warn you ahead of time. There is no telling how hot the engine got, but I must assume that there was still some water running thru the engine. Plus this is a fresh water cooled unit so you still had some cooling. If it got hot enough to do damage the mechanic that is changing out the elbow should be able to tell you. Just for the heck of it, ask the owner what RPM range he normally ran the engine at. Probably always ran the engine at 2200 or so RPM's. Also, make sure that they are putting on a new mixing elbow and not just cleaning the old one out. If the old one is not rusted thru you can clean it up and use it for a backup.
Overheating
Fred, If the overheat alarm stopped after the hose blew I don't think you will have problems with the engine. Were you running the engine above 2700 rpms for 30 plus minutes before the buzzer? How long was the buzzer on? If it was only a short period 5-10 minutes and the engine was brought back to idle or under 1500 rpms until the buzzer went off there is probably no damage to the engine. However. Had the same thing happen on a 91 37.5. As the elbow gets clogged it creates backpressure in the hose from the heat exchanger to the elbow and exhaust. The backpressure prevents sufficient amounts of cooling water to flow through the system. The water never completely gets blocked but gets constricted and causes insufficient flow for running at higher rpms. The water in the heat exchanger does not "exchange" heat fast enough and the alarm sounds. It generally happens above 2700 rpms during a prolonged engine run but can be lower depending on the amount of clogging. After the hose blows. Really just pops off the fitting at the elbow. The flow of water is restored because the blockage is bypassed and the engine should quickly cool down if you don't shut it down first. Also makes a big mess in the engine compartment because the water that is usually pumped overboard through the exhaust now just runs into the engine compartment. Since it is salt water running over the engine it can cause corrosion and rust. Clean thoroughly. The bigger problem can be that you are running the engine without any water cooling the exhaust gas. The purpose of the elbow is to mix the hot water from the exchanger with the very hot exhaust gas and get the gas and water cool enough to pass through the plastic exhaust line down to the muffler and out the exhaust port. The un-cooled exhaust can quickly damage the exhaust line. The exhaust line is expensive and hard to replace. That's where I would check closely. If the plastic hose next to the elbow is scorched, melted, burned or otherwise damaged get it replaced. If you don't you can end up with an exhaust leak inside the boat just like running your car engine inside your garage. CO is very unforgiving. Good luck. Les s/v Mutual Fun
Fred, If the overheat alarm stopped after the hose blew I don't think you will have problems with the engine. Were you running the engine above 2700 rpms for 30 plus minutes before the buzzer? How long was the buzzer on? If it was only a short period 5-10 minutes and the engine was brought back to idle or under 1500 rpms until the buzzer went off there is probably no damage to the engine. However. Had the same thing happen on a 91 37.5. As the elbow gets clogged it creates backpressure in the hose from the heat exchanger to the elbow and exhaust. The backpressure prevents sufficient amounts of cooling water to flow through the system. The water never completely gets blocked but gets constricted and causes insufficient flow for running at higher rpms. The water in the heat exchanger does not "exchange" heat fast enough and the alarm sounds. It generally happens above 2700 rpms during a prolonged engine run but can be lower depending on the amount of clogging. After the hose blows. Really just pops off the fitting at the elbow. The flow of water is restored because the blockage is bypassed and the engine should quickly cool down if you don't shut it down first. Also makes a big mess in the engine compartment because the water that is usually pumped overboard through the exhaust now just runs into the engine compartment. Since it is salt water running over the engine it can cause corrosion and rust. Clean thoroughly. The bigger problem can be that you are running the engine without any water cooling the exhaust gas. The purpose of the elbow is to mix the hot water from the exchanger with the very hot exhaust gas and get the gas and water cool enough to pass through the plastic exhaust line down to the muffler and out the exhaust port. The un-cooled exhaust can quickly damage the exhaust line. The exhaust line is expensive and hard to replace. That's where I would check closely. If the plastic hose next to the elbow is scorched, melted, burned or otherwise damaged get it replaced. If you don't you can end up with an exhaust leak inside the boat just like running your car engine inside your garage. CO is very unforgiving. Good luck. Les s/v Mutual Fun
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