Engine longevity

[Portofino]

@petem + Bruce

From my post # 10
“Assuming normal manufacturing timed schedules you can prematurely loose power by overloading them which results in soaring EGTs .
The problem with sustained elevated EGTs is the exhaust valve mushroom .It’s insidious, it’s not a Big Bang scuse the pun .
They gradually loose best seating from a hermetic pov and pressure in the cylinder thus power gradually reduces as time and continuous overloading goes on .”

Which part of insidious do you not understand ?
For ease I have copied a typical google meaning below .
“ having a gradual and cumulative effect : developing so gradually as to be well established before becoming apparent “


@bruce where did you on all the posts thus far get this impression from you posted in your post #18 ?
quote Bruce “Your EGT doomsday placard doesn't bother me too much either to be honest. I am in the camp that you'd really have to abuse the boat to develop a problem there. Nobody is going to fit an engine into a boat that is not fit for purpose. That is not to say EGT is a concern, it's just not a Damocles sword. I do not fear my engine exploding......../........”

Curious to know seeing as I said it’s “not a Big Bang “ in my post #10 .
Which post / person are you referring to suggesting some sort of explosion ?

Mushrooming of exhausts valves due to prolonged excessive EGTs is well recognised insidious reason for marine diesels apparently loosing Hp as time goes by . Certain HGV drivers fit EGT sensors too .Helps them select the best gear climbing hills loaded up .Owner operators......you know the buck stops etc .

Fouling +excess weight are the instigators .Far away from the MBY test scenarios they regularly publish which are new ish demo boats with shiny bottoms + props with partial loads and almost zero cruising stores and years of collected accoutrements so many boaters end up with .That explains your manufacturer’s and journos articles .

 

[Portofino]

I agree. The forums and FB groups are hardly awash with tales of knackered KAD engines and I imagine many have been driven hard with less than fastidious maintenance.

“Insidious “Pete .

Look up the meaning .

Explains what you say ^^^ .

Insidious definition and meaning | Collins English Dictionary

 

[Montemar]

Does your Broom 33 have trim tabs or a fixed tab? My Crown has twin 148hp VP TAMD40A’s and a set of fixed tabs the full width of the transom. Mine tops out at around 17.5 knots at WOT. I heard that the fixed tab was added to extend the hull length and increase the planing surface.
Is there a design issue with the 33 with it being a short and wide boat? From my years of sailing, there was always a thing with having large flat sections aft to help surfing down waves and planing. Shorter heavier boats would surf but not plane. Also, I had a 12ft rib with loads of power(25hp 2 stroke) and I always had to lean forward over the console to get it to plane. I think a lot of boats that are short relative to their width and weight struggle to get over the hump.

It has a fixed tab the full width of the back with a pair of trim tabs set into it. Someone who worked at Broom when the 33 was built said it was regarded as not being fast which is probably why the full width tab is there.
I wonder if there is a particular waterline length to width ratio for planing.

 

[petem]

“Insidious “Pete .

Look up the meaning .

Explains what you say ^^^ .

Insidious definition and meaning | Collins English Dictionary

I know what insidious means thank you very much.

Note that the KAD series engine is over 25 years old so I'm not sure how insidious you mean....

 

[Portofino]

I know what insidious means thank you very much.

Note that the KAD series engine is over 25 years old so I'm not sure how insidious you mean....

Replicate the mag / dealer / manufacture test results .
Copy the specs interns of fuel / water / pax / hull condition et etc to the letter .If you can with your fully maintained engines then I am wrong .
If you can’t then where’s the hp gone ?

 

[BruceK]

Porto, everyone has been telling you you're wrong for ages but you cant accept it. What makes you think we want to keep banging our heads against that brick wall for?

 

[petem]

Replicate the mag / dealer / manufacture test results .
Copy the specs interns of fuel / water / pax / hull condition et etc to the letter .If you can with your fully maintained engines then I am wrong .
If you can’t then where’s the hp gone ?

When we sea-trialled our boat when we bought it, it was only a couple of knots down on the original manufacturer's top rated speed. That was with a 15 year old turbo, 6 people on board, no doubt less than perfect propellers and many years of anti-fouling build-up.

I suspect that with new turbos, light load and someone at the helm who knows how to trim a boat for top speed, we'd be getting very close to the original top speed.

 

[petem]

Porto, everyone has been telling you you're wrong for ages but you cant accept it. What makes you think we want to keep banging our heads against that brick wall for?

Exactly.

 

[Portofino]

Porto, everyone has been telling you you're wrong for ages but you cant accept it. What makes you think we want to keep banging our heads against that brick wall for?

Wrong about exactly what .....do be specific?

 

[Portofino]

When we sea-trialled our boat when we bought it, it was only a couple of knots down on the original manufacturer's top rated speed. That was with a 15 year old turbo, 6 people on board, no doubt less than perfect propellers and many years of anti-fouling build-up.

I suspect that with new turbos, light load and someone at the helm who knows how to trim a boat for top speed, we'd be getting very close to the original top speed.

Good to know , does not conflict with what iam saying .
You claim your boat not suffered seemingly if you extrapolate theoretically from excess EGTs .So what are you trying to say ?
Thx for volunteering btw but ,....
In context of the Ops suspicion of his power loss ( maintained what ever that means ) .....he’s imagining it ?

 

[Portofino]

For Bruce + Pete Are you both saying Tony is wrong too ? Re EGTs .
Boost, EGT, and Horsepower - Seaboard Marine

 

[Portofino]

It has a fixed tab the full width of the back with a pair of trim tabs set into it. Someone who worked at Broom when the 33 was built said it was regarded as not being fast which is probably why the full width tab is there.
I wonder if there is a particular waterline length to width ratio for planing.

There’s a range it’s called the aspect ratio.Where the beam is over the waterline length @ rest .Inc this extra full width tab .

A wider beam hull benefits from a greater leading edge of lifting surface .A wide ,short hull loaded arbitrarily to keep the bow down has achieved smooth water efficiency at the expense of seagoing ability.

You might be better examining if any weight can be moved forwards , to reduce the steeper planning angle thus increase the wetted lifting area to get it up on the plane ........given the limited seemingly diminished Hp now available.

Hope this helps .

 

[Assassin]

To deal with the disagreement first, on older engines raised EGT's are not really an issue and never have been, but on newer engines they are due to the engine construction which is designed to be run within certain parameters as the components used are designed around those parameters and running high EGT's for extended periods can damage these components over time; this said any manufacturer designs their boats to run on certain engines and running any modern diesel or petrol flat out isn't an issue either, its engine overload which is the issue.
Manufacturers give running data for all their products and as long as this is adhered to then no problems should occur.

Back to the OP original question, modern engines are rated accordingly and for leisure they may be rated ay 300 HP but the same engine may be rated at only 200HP for commercial use and this relates directly to its duty cycle, this means in an industrial rating at 200 HP is still an engine designed to deliver 300 HP and if you put this engine on a dynomometer you will find it delivers more than 300 HP because manufacturers build in a buffer by exceeding its power rating so it delivers an AVERAGE 300 HP over its full designed life cycle.

 

[Montemar]

I have moved as much non-ferrous stuff forward - there is a fluxgate compass forward though it exists about a metre away from the anchor chain so could get more chain.
wine and beer are also non-ferrous so could do something there!

 

[sailorman]

For how long will a diesel engine produce its rated power if it has been maintained and still works well? Is there a slow decrease in efficiency with hours?

I re engined 28 yrs ago took out a perkie 4108 and replaced with a nanni 4150 a kubtaengjne commknly found in mini diwhen i hsd a ant fitr on site to put fhe trsck n a digger.i asmed anout the mu ota engine. He said they have mwachines with 6000hrs wth ony schuled servicig done on them.mie is up to1800rtroubke free hrs

 

[sailorman]

I re engined 28 yrs ago took out a perkie 4108 and replaced with a nanni 4150 a kubtaengjne commknly found in mini diwhen i hsd a ant fitr on site to put fhe trsck n a digger.i asmed anout the mu ota engine. He said they have mwachines with 6000hrs wth ony schuled servicig done on them.mie is up to1800rtroubke free hrs

Sorry for a typo omit 28 yrs add 18 yrs?

 

[Rappey]

A rebuild @ 8000 hrs

That's an impressive amount of hours considering how much harder a boat engine has to work.
I sold my last car with 273,000 miles. Take an average speed of 45mph and that would be 6066 hrs only. By the same debatable average speed for the car 8000hrs would be around 360,000 miles ??

 

[westernman]

That's an impressive amount of hours considering how much harder a boat engine has to work.
I sold my last car with 273,000 miles. Take an average speed of 45mph and that would be 6066 hrs only. By the same debatable average speed for the car 8000hrs would be around 360,000 miles ??

I would be very surprised if your average speed was as high as 45mph - unless you do almost all your journeys on foreign motorways!

 

[Rappey]

I would be very surprised if your average speed was as high as 45mph

I felt whatever speed I used it wouldn't be right for some so had to start somewhere ?

 

[Alicatt]

Motorcycle club did a timed rally around Caithness, I was dropping the marshals off at the checkpoints with my car and we were going hard from point to point, I did not average 30mph for the 100 mile course, which was the speed that the bikes were to average and not arrive too early or too late.