Lost of speed

[sailaboutvic]

As I posted before after replacing my engine mounts we have lost quite a bit of speed ,
i have gone in the water and found some fouling which I removed as much as I could , this as improved the speed under engine but there still in my view at less a knot less then what it was.
to reinforces this yesterday while motoring in quite a bit of wind everyone in similar boats and even smaller boat where catching up and over taken us .
2500rpm and we was making just about 5 kts , checking on AIS others where making 6 kts plus ,
yes agree I don’t know what engine are in them boats or what RPM they are using but I can only suggest them must had been thrusting the daylights especially the once with out board To be doing the speed they where doing .

I also checked on my plotter what type of speed we was doing before with 2000 rpm as that what I would normally run at ,
unless a need much more power and it was well above what we doing now at 2300rpm
just to be clear the speed lose is only under engine , under sail she still goes very well no problem 6.5 to 7 kts ,
ao it can’t be fouling .

my thought are now turning to some thing slipping , coupling or propeller, both are on a key wave , possible one key may have broken Seen unlikely but who know.
we are cruising at the moment and don’t have any pulleys with me even so for the prop it would need to come out of the water .
so here my question anyone got any tricks how to tell if the prop or shaft coupling is slipping under load ?
I could mark the shaft and coupling and see after a run if the marks have moved but I can’t think of any way to do the same for the prop .

the prop is a three blade Flexofold so there nothing in the hub that can slip and the blade are free even so if one blade was caugh or damage there be a heck of vibration.
the gearbox is MS15 and as far as I know there no clutch , unlike the sail drive that have a cone Clutch .

 

[peteK]

Check exhaust elbow,could be a early sign of carboning up.

 

[bignick]

Just to clarify, are you still getting the same max RPM from your engine, but lower boat speed, or is the RPM reduced along with boat speed?
from what i think you’re trying to describe, the first thing i would check is that the prop is opening fully. Can you dive and check it when at anchor?

 

[sailaboutvic]

Check exhaust elbow,could be a early sign of carboning up.

I would lost power if it was the exhaust elbow I can still get 3600 RPM .

 

[sailaboutvic]

Just to clarify, are you still getting the same max RPM from your engine, but lower boat speed, or is the RPM reduced along with boat speed?
from what i think you’re trying to describe, the first thing i would check is that the prop is opening fully. Can you dive and check it when at anchor?

Been in prop find clean and blade open fully ,
same RPM and can get up to 3600 RPM in gear.( under load )

im puzzled and so is the Volvo engineer I spoken to yesterday,
he insist it’s nothing to do with engine elignment other wise there be other signs vibration, banging .
spoken to the prop company they say there nothing inside the hub that would make it slip .
so now my thought are maybe a key wave on the one end of the shaft which I think it’s unlikely but hey my brain is going into over drive .

as said under sail speed no problem , so it can’t really have anything to do with fouling .

there is no doubt at all that the speed we getting now is much less then what we was getting at the same RPM before the engine mounts was replace ,
but Everyone I speak to say it as nothing to do with the mounts or alignment.

 

[Chiara’s slave]

I think you'd feel and hear any slippage in the couplings or prop. I’d check again that the prop is unfolding fully, and that the rev counter is reading true. Hows your speed at WOT?

 

[sailaboutvic]

I think you'd feel and hear any slippage in the couplings or prop. I’d check again that the prop is unfolding fully, and that the rev counter is reading true. Hows your speed at WOT?

I say WOT is around 6 kts 3600 rpm I would expect over 7kts
I been In and prop opening fine it’s clean and all blade are free ,
I can’t think of any other way of checking other then being under while in gear and I think we all agree not a good solution
any way if one blade didn’t open fully there be vibration.

 

[sailaboutvic]

Just to get to the important bits .
fouling / the boat as not lost any speed under sails on while using the engine .
engine power / I can get full RPM under load 3600 rpm
prop / clean and opens freely .
vibrations/ non to talk about
noise/ non
RPM / as most of us I know when a engine is running at a set RPM without looking at counter,
prop hub / no rubber inset in the hub.
prop pitch , no way of changing it ,

 

[Chiara’s slave]

So far, then, the most likely problem is that a young Kraken has got hold of your boat.

 

[MoodySabre]

If the shaft is slipping inside the coupling then both would get very hot. easy to check

Does that gearbox have the problem that the old MS2B had where the input shaft from the gearbox had splines that wore out and so it didn’t engage properly with the carrier ring on the back of the flywheel. This lead to complete fail of the drive and most boxes have now been adapted.

you say this has been since the engine mounts were replaced. What was disconnected and then reconnected when this job was done?

 

[sailaboutvic]

If the shaft is slipping inside the coupling then both would get very hot. easy to check

Does that gearbox have the problem that the old MS2B had where the input shaft from the gearbox had splines that wore out and so it didn’t engage properly with the carrier ring on the back of the flywheel. This lead to complete fail of the drive and most boxes have now been adapted.

you say this has been since the engine mounts were replaced. What was disconnected and then reconnected when this job was done?

Shaft coupling , and engine mounts .
foot print of old mount where marked new mount when into same foot print .
.
I keep thinking it as to be something to be with the engine enligmeant as it only started happen since .
but no vibration and the coupling line up within 0.002 and told it nothing to do with it ,
so I really have to stop thinking it is.
but I’m really now lost where else to look other then some thing slipping ,
my thos are now going towards the gearbox .
It as the Volvo engineer I spoke to yesterday said , his grasping at straws , I got him thrown .

 

[bignick]

Can you borrow a handheld optical tacho? That would allow you to check what rpm the shaft is doing just before the stern seal, and confirm whether it is the same as the engine. It would be a clear indicator as to whether your problem is inside the boat or outside.

 

[oldmanofthehills]

I have had slipping coupling, but it overheated and gave up right in the mouth of Cardiff lock, so similar should be easy to diagnose .

The other altervative is a slipping cone clutch and I bought a boat with such where it was very uncertain if boat could get to full speed reliably, though revs were fine. Sellers engineer denied the problem, but surveyor raised it as an issue, I dropped price and eventually after one year the slipping became unmanageable at any speed above creep.

As it happened I did not like the engine as had other failings so changed it plus gearbox as rebuild costs for whole shebang were unreasonable

The good news is that it is quite possible to change the clutch, and I have done so on an earlier boat, though one needs bearing puller plus of course the replacement clutch. Being tight I just reversed the clutch so I got slippage going astern instead as never wanting to go 4kts back out of finger berth

 

[sailaboutvic]

Can you borrow a handheld optical tacho? That would allow you to check what rpm the shaft is doing just before the stern seal, and confirm whether it is the same as the engine. It would be a clear indicator as to whether your problem is inside the boat or outside.

I been trying to get scope app but so far cant fine one that works at less that would give me some kind of way to turn .
as anyone found a good app ?

 

[MAURICE]

It seems that the engine is fine when not under load? it sounds as if you have tried everything else. Have a go at cleaning the injectors maybe they are fouled you can get some injector cleaning snake oil which you put in diesel. its worth a try

 

[peteK]

I would lost power if it was the exhaust elbow I can still get 3600 RPM .

I have an engine with the same exhaust elbow I could still get 3600rpm but with reduced power and it was the exhaust elbow restricted with carbon,thats why I said early signs,keep using the engine and eventually you will have reduced revs,as you should be aware these exhaust elbows are known for it.

 

[sailaboutvic]

It seems that the engine is fine when not under load? it sounds as if you have tried everything else. Have a go at cleaning the injectors maybe they are fouled you can get some injector cleaning snake oil which you put in diesel. its worth a try

Thanks Maurice but would you not tho if it was an injector there be other sign of lost power ?
engine seen to be running fine .

 

[sailaboutvic]

I have an engine with the same exhaust elbow I could still get 3600rpm but with reduced power and it was the exhaust elbow restricted with carbon,thats why I said early signs,keep using the engine and eventually you will have reduced revs,as you should be aware these exhaust elbows are known for it.

Peter I know of these elbow normally one of the first signs of over heating as the water flow is restricted, I have plenty of flow and no over heating , although after saying this I will once we return home take it off and clean it .
while we on the way i don’t want to remove anything that I have no parts for , ie gasket

 

[lustyd]

Shaft coupling , and engine mounts .
foot print of old mount where marked new mount when into same foot print .
.
I keep thinking it as to be something to be with the engine enligmeant as it only started happen since .
but no vibration and the coupling line up within 0.002 and told it nothing to do with it ,
so I really have to stop thinking it is.
but I’m really now lost where else to look other then some thing slipping ,
my thos are now going towards the gearbox .
It as the Volvo engineer I spoke to yesterday said , his grasping at straws , I got him thrown .

There wouldn’t be vibration if misaligned it might just rub hard against the cutless.
Was the shaft centred when you measured? They are quite heavy so when unsupported can droop which would mean you purposefully misaligned it to 0.002 against a wonky shaft. Not suggesting you did but worth asking.

 

[sailaboutvic]

There wouldn’t be vibration if misaligned it might just rub hard against the cutless.
Was the shaft centred when you measured? They are quite heavy so when unsupported can droop which would mean you purposefully misaligned it to 0.002 against a wonky shaft. Not suggesting you did but worth asking.

Good point , it’s wasn’t possible in the water to know where te centre of the tube was but the engine coupling was about a CM higher then the shaft coupling , to take account the weight of the shaft .
one thing I will do once back is dry out and slide the seal off to check how centre it is .

but according to Volvo even a bad misaligned engine wouldn’t cause lose of speed .
although this is some thing I will check in time ,