Increasing low load engine temps and extending HE service intervals.

[No control]

We still aren't ready to pull the trigger, but as I spend my time reading and learning, a few questions have come to mind.

Low load engine temps. I see this mentioned all the time about how it's a really good idea to run the engines up at the end of the day to burn off all the crap that accumulates due to low load and low running temps. I've read that for those that spend their time at hull speed, derating the engine and propping up for the target speed range seems to be the solution. But in lieu of that, has anyone installed a thermostat in the raw water circuit that bypasses the HE and returned to the system at the exhaust manifolds? Similar to putting card board in front of the radiator on really cold days. I've never seen anyone mention this, so I'm not sure if it's been tried and not worth it or if I somehow have bumbled my way into something nobody else has.

I've also read that the HE cores need to come out roughly every five years or so for decalcification. Understandable as they're immersed in raw water nearly constantly, I presume. Would installing a fitting downstream of the raw water pump to run fresh water through the raw water circuit at the end of the day help any? Similar to flushing an outboard or I/O out. As with the other thought, I've never seen this mentioned...

Thanks, and I look forward to the discussion.

 

[Captain Ralph]

Reading the B S on the internet can cause lots of confusion and headaches. Don't try any mods to the engine (any brand).

I run my 43+ year old, 12V71TIs out about every 10 to 20 hours. Now, here up the St Johns river, that would be weeks in between.
When in open water, run yours against hull speed for a few minutes before you start any long trips to ensure all is good.
Just before you leave that open and deep water returning, load them up just a little to blow out any gunk.
Take care of the oil changes and good fuel. Take a sip and sleep well.

Oil labs will help determine any concerns if any.

 

[brico]

I fully agree with Captain Ralph's feedback. On my 1980 Hatteras 37 powered by twin DD 6-71 Naturally Aspirated ( I have been given to understand they have superchargers or rotoblowers, whatever they are called) I run my engines at 1250RPM most of the time and only very occasionally I run them up to 2400RPM which is WOT for about an hour each season. On this boat with these engines it is either 1250RPM to achieve 8.5 Knots or >2200 RPM to get her close to planing speed, anything in between is pushing a massive wave in front of the boat at 11 knots at best and bow raised high up in the air. With my trim tabs not working I do not bother going to the planing speed at any length so I mostly chug at 1250 RPM and 8.5 knots(I should have bought a trawler type boat because I enjoy that speed ). My (engine and transmission) oil and coolant analysis have returned with excellent results after each two year (200 hour) running periods.

 

[brico]

I forgot to mention that when I purchased my 1980 Hatteras 37 in 2014 I opened up the HE elements and found them badly fouled with calcification. The engines were not overheating but... Since then, and because the HE covers provide that possibility on DDs, I fitted the drain with a hose and a ball valve at the end, and I drain the raw water into the shower sump, when I stop the engine for two or more days with out running. That way, there is no salt water standing in the HE and slowly but surely calcifying and blocking the flow of raw water and the needed heat exchange. I have to admit that I have not opened up the HE covers to see if this drain has made a difference in the accumulation of calcification and blockage of HE that I've found when I purchased the boat. Fitting the fresh water flushing system is a good idea too but it requires more fittings and more time to complete than simply draining the raw water from the HE core. I am tempted to open up my HE covers to see if I have achieved what I intend to with fitting the drain. This way it made me to enter my engine room(space rather than the room) every time before I start the engines and it makes me look around and check oil level and fuel filters before starting engines in addition to routine checks every 6 hours of running.

 

[Briankinley2004]

R A Clarkson had a thread on here where he put a ball valve with hose adapter on his raw water system to flush them out after every use. I was going to do something similar in my spare time, which has a zero balance. He hasn't been active lately but a search will probably find the post.