New props, now not quite running at max revs

Either the Volvo agent is looking forward to charging for repairs of they haven't a clue. It could be that Volvo's do not suffer with overloading like all other deisels but I doubt they are that special.

Tony of sbmar reckons that you should always shoot for a hundred or so over recommended wot. Then the engine load remains low giving better life and allows for weight, dirt etc without killing the engine. Egts ramp dramatically when overloaded and will have a big effect on the engine long term.. otherwise we would all be sticking big props on to get more speed for free....

Steve
 
5teve said:
Either the Volvo agent is looking forward to charging for repairs of they haven't a clue. It could be that Volvo's do not suffer with overloading like all other deisels but I doubt they are that special.

Tony of sbmar reckons that you should always shoot for a hundred or so over recommended wot. Then the engine load remains low giving better life and allows for weight, dirt etc without killing the engine. Egts ramp dramatically when overloaded and will have a big effect on the engine long term.. otherwise we would all be sticking big props on to get more speed for free....

Steve
Click to expand...

+1
I was a bit staggered by the contents of post #20 , lost for words .
You have written what I was thinking :encouragement:

This whole thread and the other re “can’t reach rated rpm “ is crazy after fitting a bigger prop imho .
 
k, had the laser rev unit out today, my VP rev display is accurate at 500 1000 and 1500 revs in neutral

B2 = old props:
3000 revs 18.0 knots 04/2019
3600 revs 24.5 knots 04/2019
Rev limiter cutting out with ‘old’ B2 props at 25 knots = 3750

B5 = new props:
3000 revs 24 knots 05/2019
3500 revs 29 knots 05/2019

leg trim, still need to check this on flat water, have been running it too far in / down, -8, for all of the above numbers
too choppy today to blast it, which i rarely do, potter at 1000 is more like it :)
 
just read post 20 - I agree with the other posters this is a seriously bad idea.
the improved speed is impressive however at best you will be burning the turbo charger exhaust impeller, worst case you will melt an exhaust valve then it's bye bye engine.
 
Agreed the improved speed is good - but what condition is the boat in? Loaded up with stuff you would normally have on board? How dirty is the bum and running gear and how many people?

You can see its already overloaded if your figures are workable (you dont mention WOT) as its 250rpm short of max rated (if the limiter kicks in - otherwise you should be aiming for an easy 100rpm over rated RPM) If you only had one or 2 persons were clean as and lightly loaded - then things will only get worse and more overloaded.. again it should be achieving these revs with ease not labouring to get on the plane.

So if it was loaded up and had multiple passengers and was dirty.. you probably have scope for bigger than original props.. but not as big as you have gone..

Have a read... https://www.sbmar.com/articles/engine-life-vs-engine-loading/

https://www.sbmar.com/articles/engine-life/

Steve
 
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