Engine rebuild or replacement

[dmr]

1 hour ago, Alan de Enfield said:

 

No, because the boat will have been designed to take the power / weight / thrust etc of the engine running on 4 cylinders. Just because you've allowed the engine to fall into disrepair will not affect that.

 

But you are probably thinking of boats like yours, big plastic seegoing things with very high powered engines.

I doubt that many (any) narrowboat builders do any design relating to the power of the engine, they just build their standard shells and put an engine in.

Maybe some bearers change for very big or very small engines, but I wouldn't even bet on that.

The size of the prop shaft could be a design thing, but the transient forces from the prop hitting something will far outweigh any engine forces.

[ditchcrawler]

16 hours ago, dmr said:

 

There is a good amount of knowledgable people who believe that almost all engine wear happens when starting an engine from cold , so trying to extend engine life by only running for an hour is a hiding to knowhere. These people also say an engine should never be shut down till it is fully warmed up. So, having lots of batteries and running an engine for many hours maybe once every other day is probably the best way to look after an engine.

The old wisdom of an hour every morning and an hour every evening is probably not too good.

That was our routine at work, start the standby generators and put them online for the morning, not just run them up and shut them down, same with pumps

[MtB]

23 hours ago, dmr said:

These people also say an engine should never be shut down till it is fully warmed up.

 

What's the rationale here please? 

 

It's hard to imagine how stopping an engine at any particular point in the warming-up cycle could make any difference to wear.

 

 

[ditchcrawler]

6 minutes ago, MtB said:

 

What's the rationale here please? 

 

It's hard to imagine how stopping an engine at any particular point in the warming-up cycle could make any difference to wear.

 

 

Condensates in the oil and internal parts of the engine is what I was told that form when you start a cold engine, if you get it to full working temperature they boil off

[cuthound]

BT used to run their standby generators monthly to test them. Always to the building load and always until oil and water temperatures had stabilised, typically 10-15 minutes.

 

I was told on my basic generator maintenance course over 50 years ago now that 90% of the wear takes place during start up and the warming up phase, partly because the oil is cold and thick and hasn't circulated properly.

 

To minimise the wear and to allow the generator to start at full design loaf BT used electric crankcase heaters to maintain the engine water jacket at normal operating temperature.

Edited December 24, 2023 by cuthound
Clarification

[ditchcrawler]

3 hours ago, cuthound said:

BT used to run their standby generators monthly to test them. Always to the building load and always until oil and water temperatures had stabilised, typically 10-15 minutes.

 

I was told on my basic generator maintenance course over 50 years ago now that 90% of the wear takes place during start up and the warming up phase, partly because the oil is cold and thick and hasn't circulated properly.

 

To minimise the wear and to allow the generator to start at full design loaf BT used electric crankcase heaters to maintain the engine water jacket at normal operating temperature.

On some of out pumps we had manual lubricating oil pumps that you were supposed to crank to get the oil round the engine before stabbing the button. 

 

[cuthound]

1 hour ago, ditchcrawler said:

On some of out pumps we had manual lubricating oil pumps that you were supposed to crank to get the oil round the engine before stabbing the button. 

 

 

Yes some of our biggest gensets had "donkey engines" which you started first to prime and circulate the oil system before the engine started. 

[magnetman]

I recall the 600hp Volvo marine units had a setup where fuel injection was timed to take place after several rotations of the crankshaft using the starter motor rather than fueling immediately.

 

Seemed a Good Idea. 

 

 

My old Perkins P4 has a manual lube pump. Never used it though. Maybe it would help with cold starting not that it is a problem.