Cummins 4bt overheating after conversion keel cool to heat exchanger

Cummins parts are about the cheapest you can buy in the marine diesel business, and they have produced/sold such a large volume of motors that the used market is huge also.
Good luck finding similar parts at 1/5th the price.
Cummins invests heavily in R&D in order to maintain their market share.
I would utilize their experience and expertise before I tried to "re-invent the wheel".

 

a few notes from the OP....
- the problem has been solved months ago, as posted earlier.
- Although the temporary electric seawater pump was undersized and would not have been able to keep engine cool at Wot, it was able to keep it cool at cruise speed, until I bought and installed the proper gear driven seawater pump.
- the actual reason for the overheating was the undersized coolant tank, which could not prevent air being trapped as the reservoir volume was not great enough.
- for me,it was not an effort in futility... I appreciate all of the help and was able to use the boat many times throughout the summer, after the issue was solved.

For the record, as described earlier I believe, the reason for the use of temporary parts was to allow me to sea trial the boat, which I spent 3 winters of weekends to build, and prove to myself (and my wife..) that it meritted more time and money this winter in refining systems, welding in a permanent aluminum floors, etc.
This was sea trials / performance was successful and as mentioned i have since upgraded the seawater pump, fabricated and installed a wet exhaust elbow and hose, etc.

 

Using an electrically-operated sea-water-pump - with but a fraction of the OEM (Cummins) pump´s flow-rate - is hoping for a miracle !

 

Absolutely. A quick peep on EBay reveals Cummins exhaust manifolds going for around 500 bucks.

People looking for stuff at 1/5 that price........ I suppose they are entitled to disclose their wish-list in public and /or their extraordinary business accumen.

 

I am not sure how to state it any more clearly (other than in plain text several times..) I was not hoping for a miracle..or any long term use from the electric pump! It DID allow me to try the boat out, and see the other areas of performance were OK, before spending the $500 on a gear driven pump.

re: Cummins prices, you can get something like an aftermarket or used wet exhaust elbow for about $500-600 on Ebay, but from the dealer it's over $1000. I am sure there are engine manufacturers with even more expensive parts, but this is still over-priced.

I tig welded my own wet exhaust elbow for about $60 in 316 stainless pipe and maybe 3 - 4 hours labour.
If you have a new $20,000 engine, then paying high prices for parts is relative. When you pay $2 or 3K for a good complete used engine (minas the wet exhaust elbow as it had been keel cooled/ dry stack) you are not as eager to pay $1000 for an oem elbow.

 

The objectives that you established were sound.

Criticism has been directed at how you went about attaining them.

Next time around spend some time reading up and understanding the input/output specs and carachteristics of the different OEM marine parts, such as the sea-water pump, heat exchanger, header tank dimensions and internal details, fresh-water (or sea-water) cooled exhaust manifold, turbo, charge-air cooler etc...