Fresh water engine flush

[djpcep]

On my photo album Nos. 4, 5, & 6. I have shown my solution to flushing the engine with fresh water after a sea trip.
Engine flush 1. shows where I have inserted a 1½" equal T (nylon from Home Depot) into the feed line for the marine head. (Well above the water line).
Connected to this I have a black 1½" hose (West Marine) and run it round the back of the holding tank to the point in the back of the aft locker wher the wash-down supply exits. (Engine flush 2.) Here I cut a hole and inserted the connector I had left over from my wash-down modification. On the outside (Engine flush 3.) you can see the new brass angled wash-down connection and the old one now used for the engine flush.
Operation With the boat either in or out of the water connect a garden hose to the flush connector and leaving the sea cock open, turn on the water supply to full flow. The water should then pour out of the sea water intake under the hull.
I reckon that the sea cock should stay open to avoid pressure on the inside of the sea strainer. Closing the sea cock could blow the glass dome !!! I do not intend to try!!
Run the engine, keep the water flowing, and stop the engine before turning off the water supply.
I reckon this will work in or out of the water.
If anyone thinks that there are any probleme with this arrangement do let me know.

 

[commander bill]

I have not a detailed study of your design but please beware that you do not want to pressurize your water supply to the engine raw water pump on inboard engines. The exhaust system is designed to handle raw water flow while the engine is running but you can cause water to enter the engine cylinders if pressure is used prior to starting the engine. This will result in significant engine damage. You are probably avoiding this by keeping your hull valve open allowing excess water to spill overboard. This goes well beyond the concern of breaking the dome cover. That is also why you do not want to continue trying to start an engine beyond 20-30 seconds if there is a starting problem.

I have found that it is easy to run my engine by just taking off the dome cover and allowing a water hose to pour into the strainer (with hull valve closed) any excess water will just spill out into bilge. Works great with boat on trailer & drain plug removed. You can easily throttle the hose flow to match the water flow needed to keep strainer full. However, this will not allow you to increase engine speed much because cooling water demain increases very fast beyond what you can makeup. Also, for those with boat in water full time I doubt this helps much. Also, takes quite a whaile to heatup engine this way if your intent is to change oil.

 

[djpcep]

Bill,
Thank you for the warning.
I'll be very carefull with the pressure.
Dom

 

[Stella Maris]

Bill,
Your method will also work with boats in the water. Just be sure to CLOSE the seacock before removing the dome.

 

[commander bill]

I would think that djpcep's method would be better for a boat in the water. I guess my method could be used but all the excess flow would have to be pumped out with bilge pump. When I do this on the trailer I usually do not worry about excess flow as it all drains out open drain hole. Of course I am thinking of running engine for extended time to warmup for oil change.

I also considered that djpcep's modification could also be extended with another "tee" to provide the priming source we sometimes need for our AC seawater pump (only needed when first placed in water). Pump will remain primed after all air is finally displaced as long as boat stays wet.

 

[djpcep]

A modification to my arrangement would be to add a stopcock next to the equal "T" as I think that the extra volume of air in the feed pipe inhibits the efficiency of the head pump in drawing up water from the sea strainer. DJP

 

[Levitation]

I just pop the top if the sea strainer, lay a hose in the basin and let the water run while I go start the engine... I then reduce the hose flow until is is just rinning over the top of the basin as tne engine runs...
I accomplish two aims: Flush the engine and the overflow goes to the bilge and flushes the bilge pump and line...

 

[commander bill]

This is the same as I have done. Boat on trailoer, Overboard valve closed, dome off, water hose keeping strainer full, overflow flushes out bilge, little dishwashing soap into bilge helps. Only problem I have had is that it takes very long to get engine up to operating temp on idle and if I attempt to operate engine at elevated RPM you quickly reach the point when you can't keep the strainer full (engine is pumping water from strainer faster than hose will keep it full). However, it does warm the engine enough to heat the oil enough to allow portable oil pump to extract oil for a oil change.