Lost of speed

[Pye_End]

Sails may well offer more power than engine. Perhaps the comparison is not a correct reason to discount hull fouling.

If the engine is reaching full rpm under load, the problem is not the engine, as you surmise.

I have an app called RPM Meter Strobe Light (Android). Havn't used it for this purpose, but can't see why it wouldn't work. Observing shaft speed for this must be really useful in problem diagnosis.

Are you sure your boat speed analysis is correct?

Wear on prop?

 

[sailaboutvic]

Sails may well offer more power than engine. Perhaps the comparison is not a correct reason to discount hull fouling.

If the engine is reaching full rpm under load, the problem is not the engine, as you surmise.

I have an app called RPM Meter Strobe Light (Android). Havn't used it for this purpose, but can't see why it wouldn't work. Observing shaft speed for this must be really useful in problem diagnosis.

Are you sure your boat speed analysis is correct?

Wear on prop?

Thanks I check this app out .
yes 100% speed is lost at tho RPM ,
inow looked back to similar days and condition we for sure losing speed under engine , I did start to think it was my imagination but my wife agree ,
the other day was a conformation in a bit of a chop and wind everything came pass us we was at 2800 RPM when I say every thing much smaller boat with out board .
if was not funny .

 

[sailaboutvic]

Sails may well offer more power than engine. Perhaps the comparison is not a correct reason to discount hull fouling.

If the engine is reaching full rpm under load, the problem is not the engine, as you surmise.

I have an app called RPM Meter Strobe Light (Android). Havn't used it for this purpose, but can't see why it wouldn't work. Observing shaft speed for this must be really useful in problem diagnosis.

Are you sure your boat speed analysis is correct?

Wear on prop?

Downloaded the app , how is it supposed to work .

 

[Pye_End]

Downloaded the app , how is it supposed to work .

Work out shaft your shaft speed for a given revs - ie engine speed / reduction. Mark shaft eg with a sharpie, or find other distinguishing feature. Set the strobe to same speed. Press zizzy button. Shine on shaft. Check shaft appears stationary.

 

[sailaboutvic]

Work out shaft your shaft speed for a given revs - ie engine speed / reduction. Mark shaft eg with a sharpie, or find other distinguishing feature. Set the strobe to same speed. Press zizzy button. Shine on shaft. Check shaft appears stationary.

Ok got it working , just got to test it out now .

 

[geem]

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

Our generator loses power when the exhaust blocked. The engine would still rev to 3000rpm but wouldn't run the same load. I can tell when the exhaust is blocked as the engine runs rougher, there is more vibration and reduced water flow
If you are running to the same revs as before and its not an exhaust elbow problem then I would suspect a gearbox issue

 

[sailaboutvic]

Our generator loses power when the exhaust blocked. The engine would still rev to 3000rpm but wouldn't run the same load. I can tell when the exhaust is blocked as the engine runs rougher, there is more vibration and reduced water flow
If you are running to the same revs as before and its not an exhaust elbow problem then I would suspect a gearbox issue

Tim engine run fine no short of water coming out of the exhaust .
no vibration to talk off , no over heating .
next time out I can now put a strobe light on the coupling that hopeful will tell me if there something slipping in the gearbox .
It’s really getting to me now , and althought I been told many times by engineer I spoken that any alignment wouldn’t cause the problem , it all goes back to changing the engine mounts , straight after ,
we sat in a marina for 10 days while working on the boat and doing personally stuff then the problem .
once back home I start take things apart if I don’t get to the bottom of it , but in the mean time we have some motoring to do ,
we be entering the Dutch inland water in a few days , so there going to be four or five days motoring .
maybe people can see why I like to get it sorted before then
plus using so much RPM we burning fuel like no tomorrow .

 

[jamie N]

For some reason could it be your propeller not fully opening?
(I realise that the linked video shows a reversing issue......)
I realise also you've manually moved the blades and they seem to be loose, but it's the only thing that could give the symptoms you describe.

 

[sailaboutvic]

Ok I manage to do test the shaft rpm on the pontoon,
give or take 5 they are as I would expect .
1500 rpm 625, 2000rpm840 2200 940 2500 rpm 1070
gearbox is a 2.35/1
soi can now forget the gearbox and the shaft coupling.

 

[sailaboutvic]

For some reason could it be your propeller not fully opening?
(I realise that the linked video shows a reversing issue......)
I realise also you've manually moved the blades and they seem to be loose, but it's the only thing that could give the symptoms you describe.

I think it be very clear if one of the blades wasn’t opening as it’s a three blade prop .
I can see it happening on a two blade
thanks for the link .

 

[LittleSister]

As I pointed out in your previous thread, if your engine is producing the revs you have called for with the engine speed control, then loss of power cannot be the problem, If it was, then the engine would not be able to maintain that engine speed - i.e. it would fall from, or keep frequently dropping below, 2,500 rpm.

The engine speed control DOES NOT work like a car accelerator (i.e. increase control setting = increase fuel supply and hence power) The engine contol lever control sets the engine speed, the automatic governor in the engine will deliver as much or as little fuel is required to reach the revs called for. If the power available from the engine is inadequate to reach those revs - because the boat propellor is incorrectly sized for the engine/boat combination, the engine cannot produce its designed power (due to e.g. injector/elbow etc. problems), or the boat is grossly slowed by e.g fouling or abnormally strong headwind - the revs will fall and be unsteady If the engine is steadily maintaining the 2,500 rpm, then shortage of power is not the problem. If the engine can reach maximum revs under load then shortage of power is not the problem.

It remains a mystery!

 

[sailaboutvic]

Quickly running out of things to look for ,
I now know it’s not lack of power , or the gearbox , it don’t leave much else .
prop key , propellor or as suggest blades not fully opening but I would tho that be noticeable.

 

[AntarcticPilot]

Quickly running out of things to look for ,
I now know it’s not lack of power , or the gearbox , it don’t leave much else .
prop key , propellor or as suggest blades not fully opening but I would tho that be noticeable.

I don't know the model of prop you have, but on my Gori one, the blades are linked by toothed sectors so both blades have to open to the same extent. Of course, if the prop doesn't open fully, then neither blade is fully extended, but the prop is still symmetrical so there's no vibration. As I say, I don't know your make of prop, but it doesn't follow that a failure to unfold properly will result in vibration.

Mine occasionally fails to unfold properly in reverse; the symptoms are loss of power, but no vibration of other symptom.

 

[sailaboutvic]

For some reason could it be your propeller not fully opening?
(I realise that the linked video shows a reversing issue......)
I realise also you've manually moved the blades and they seem to be loose, but it's the only thing that could give the symptoms you describe.

Thinking a bit more if all the blades come out part of the way yes that would cause a problem .
thanks for the suggestion

 

[sailaboutvic]

I don't know the model of prop you have, but on my Gori one, the blades are linked by toothed sectors so both blades have to open to the same extent. Of course, if the prop doesn't open fully, then neither blade is fully extended, but the prop is still symmetrical so there's no vibration. As I say, I don't know your make of prop, but it doesn't follow that a failure to unfold properly will result in vibration.

Mine occasionally fails to unfold properly in reverse; the symptoms are loss of power, but no vibration of other symptom.

Agree , it’s a flexofold three blades so it is on gear teeth.

 

[MontyMariner]

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 .

I would think along the same lines as you. Basic faultfinding technique, 'what has changed', you have looked into misalignment, the only other thing that could have changed is the prop distance from the hull, so that's worth a check.

 

[jamie N]

I was thinking of the above also: if the propshaft had been moved enough to inhibit the fully open position on the prop.
I reckon that we're getting closer....

 

[sailaboutvic]

Shall I throw another spanner In the works ?

just been down to check the prop again ,
it open freely , just with my finger tips , had a good look around in between gasping for air and can’t find any thing that may restricted it from opening ,
im now totally lost .

engine rpm checked ok ,can’t be lost of power
shaft rpm checked ok , can’t be clutch slipping ,
prop checked ok I can’t see any thing to stop it opening ,
sailing speed ok cant be fouling ,
must be missing some thing ,

 

[sailaboutvic]

I would think along the same lines as you. Basic faultfinding technique, 'what has changed', you have looked into misalignment, the only other thing that could have changed is the prop distance from the hull, so that's worth a check.

Before moving the old mounts I marked the foot print the new once when in the same place so the engine is no further back or forward then before , plus the rope cutter slot for the part that don’t move is back in the slot which confirm the shaft is in exactly the same place .

 

[Pye_End]

Really pleased the strobe thing worked.

In terms of likelihood, I would put my money on light fouling or perception or a mixture of both. Comparison with other boats or with sailing speeds are inconclusive as there are other variables.

Where are you? Cuxhaven has scrubbing posts (I went through similar thoughts to you after struggling through the Kiel Canal 29 years ago in time, and got in just after dark!) - but I guess you are well past there.