See full version: Omc Cobra Water Flow Diagram
Home about. Technique to remove broken drive shafts. Omc cobra how to change a water pump impeller in omc cobra stern drive how to replace a water pump how to repair a stern drive is a short video to show you how easy it is to repair the water.
I took this video to show the water flow from the lower unit to the water pump impeller housing without the engine running. Look for a pee hole in the lower case and a nipple on the inside that a hose would connect. I have a 93 omc cobra outdrive 5 liter ford based engine. here
Omc sterndriveomc cobra fuelcooling systems water circulating pumps see page 167 168 for additional information all sierra water pumps are bi directional 18 3575 water circulating pump replaces. Lift the water pump housing off the top of the. Servicing the omc cobra impeller is very similar to doing so on most other outboard motors. more
The diagram below shows the water flow thru the drive. The impeller sits inside the water pump housing on the top of the gear case. Adjusting the shift cable troubleshooting the engine starting with the carburetor. more
Outboard motors rely upon simple mechanical systems that push water through the engine in order to maintain temperature and avoid overheating. When water flow through the outboard motor is disrupted or stopped entirely, overheating occurs. Here are top four things boat owners can do when they notice that water is not circulating through the outboard motor:
1) Check the Water Pump Impeller
4) Check the Thermostat
This water pump is located in the upper gear housing of the outdrive. Real easy to get at. more
Re: Low water flow from a 1991 OMC Cobra outdrive [links]
Re: Low water flow from a 1991 OMC Cobra outdrive
I have a 1991 5.8 liter OMC engine with a cobra outdrive. The engine is over heating and I have narrowed it down to lack of good water flow from the outdrive. When I put the garden hose on the outdrive the engine runs nicely at 160 degrees. When I run it in the water, the engine quickly heats up to 200 degrees. I have replaced the impellar but not the housing. I have also replace the water intake hose located in the gimble housing. When I force water out from the hose at the thermostat housing with the impellar housing off, I get good water flow out. The intake screen seems to be clear. You should also know that last year my out drive was repaired and the propellar shaft was replaced. Not sure if this would impact the water flow at all; but I thought I would post it anyway.
Short of taking the outdrive apart to see if there is any obstruction between the upper gear housing and the intake screen I don't know what else to do.
Thanks for any help you can give.
Proper cleaning is a two-step operation. First, clean the unit with a strong alkaline solution to remove organic dirt such as oil. Second, clean the unit in an acid solution to remove scale. The most drastic solution is to remove the heat exchanger and take it to a radiator shop for a complete cleaning. Make sure that the radiator shop has experience with marine heat exchangers. [links]
Besides the direct damage that a raw-water leakage can do, it may also be a warning signal for other problems. Leaks may start due to pressure build-up in the system resulting from raw-water blockage in either heat exchangers or exhaust system. [links]
External leaks
External leaks on the raw-water side seldom create major problems until they reach a high level. They should be fixed since a small leak easily could develop into a major one. Raw-water can do major damage if allowed to encounter other components, especially electric ones. [links]
Heat exchanger defects
Since heat exchangers contain no moving parts there is very little that can go wrong with them except that they can be plugged with debris and that they will become dirty. They can also develop internal and external leaks. Leaks will be covered in the next category of troubleshooting. There is also the possibility that a heat exchanger is insufficient in capacity and/or incorrectly manufactured. Those problems, however, will show up immediately upon start-up and the manufacturer should be contacted. In this discussion, we are concerned with the problems that could develop during normal usage. here
Engine internal blockage
It is very unusual that a freshwater-cooled engine would have this problem. If an engine that has been operated on raw-water is converted to FWC, it is possible that old rust and scale deposits will create restrictions. That is why it is important to try to remove as much of this rust and scale as possible, as part of the installation process. Some of the debris may not come loose until normal engine operating conditions with higher jacket water flow, heat, and vibration. It is unusual that this debris will create blockage within the engine. More likely, it will be flushed along and are struck in the heat exchanger. here