MD 2030 follow up

[sailaboutvic]

Wind and current the same during speed tests?

We didn’t really need any test to tell me the boat was having a problem , but all the same as we left Kalunborg we did several Runs using gps and log in no wind and very little current and there was no doubt the boat wasn’t performing the way she did before we arrived .
which is why I posted .

she performing better now ,
the last two days under sail we seen 6.6 /7 knots again .
under engine she gain a Knot , she needs a lot more cleaning so I’m hopeful she be back to her self soon .
im also glad that the problem was found I started to think I cocked the job up.

just to add I’ve not lined an engine up before , I know and read the theory but that’s not the same as having experience doing the job especially when it don’t go to plain .
it all seem straightforward ,
take photo, mark the foot print of the old mounts , measuring the heights , even counting the thread ,
that’s all well and good if the engine was spot on in the first place.

when things do go wrong you start to ask question like is 0.002F too far out of can 8 f still be ok ,
can 5mm from Side to side be enough to cause a problem ?
lots of unanswered questions .

in the end a call to a volvo engineer,
he insists an engine slight out will cause a lost of power, when ask how much out he couldn’t say ,
he also insists engine mounts never need changing unless I caught a rope and damage them,
in which case I probably got a bend shaft , which is why I was getting vibration.
even though I explain that the vibration was when the boat was in neutral.
i wasn't going to get into a discussion about rubbers getting soft over time or oil, who am I to argu with a Volvo engineer.
in the end he suggest I had a bend shaft which is why I had vibration and now got lost of power ,
well at less he chatted to me ,


because the boat has only been in the water a couple of months and my experience of CC over many years add to that when I hauled out todo the rudder there was very little fouling after a season in use ,
I focus that I must had missed some think .
so I made the mistake of discounting fouling.
stupid mistake on my part.

I always like to report back if I ask a question so other will know what I found and like in this case learn by any mistake I made .

 

[westernman]

They could perhaps have prevented the engine reaching the specified revs, but as it did achieve those revs, they are irrelevant.

Barnacles on the propeller can have the effect of reducing thrust without affecting RPM.

 

[sailaboutvic]

Barnacles on the propeller can have the effect of reducing thrust without affecting RPM.

Funny enough the prop was clean ,
but the rudder and from just before the prop the hull had tons of very small barnacles , just touch them and they fall off .

 

[LittleSister]

in the end a call to a volvo engineer,
he insists an engine slight out will cause a lost of power, when ask how much out he couldn’t say ,

He is correct that an engine slightly out will cause a loss of power, but that is irrelevant to the problem you reported. The engine was generating enough power to reach the 1,800/2,000rpm at which you were comparing boat speed before and after.

If lack of power were the problem, then the engine revs would fall - you would not be able to maintain the 1,800/2,000 rpm you were setting for comparison, not that the boat would go slower at the same revs. A lower boat speed at the same revs can only be either additional load (e.g. hull fouling, headwind) or reduced thrust (e.g. fouled or damaged prop, clutch slipping)

Given the engine was apparently able to maintain the revs you specified, whether the engine had 0hp or 100hp in reserve at those revs won't affect how fast the boat goes at those revs. That is a function of the load that the boat (in the particular conditions) places on the engine at those propellor revs and the thrust the propellor can generate. Whether or not the engine had enough power to reach its maximum revs (which I assume are rather higher) would affect the maximum boat speed you could obtain, not the speed at the particular revs.

 

[LittleSister]

don’t have a tachometer so that out .

I think you were saying you don't have a hand-held tachometer to check the engine tachometer is reading accurately.

There are cheap phone 'tachometer' apps you can use to do such a check. They flash the phone's torch/camera flash at a specified speed. With a mark (bit of tape?) on the flywheel or accessory drive belt pulley you can establish what speed the engine is turning.

 

[sailaboutvic]

I think you were saying you don't have a hand-held tachometer to check the engine tachometer is reading accurately.

There are cheap phone 'tachometer' apps you can use to do such a check. They flash the phone's torch/camera flash at a specified speed. With a mark (bit of tape?) on the flywheel or accessory drive belt pulley you can establish what speed the engine is turning.

To be honsty I been around boat long enough to know roughly what a boat was doing or if had a problem , really didn’t need log or GPS to tell me the boat wasn’t doing what it use to do .
even without a rpm counter , I can tell within a couple of 100 rpm what the rpm is.

within 5 mins of leaving the marina it was very clear I had a problem.
it was that obvious in speed lost .
my brain told me as I could still get full rpm that nothing wa binding and stopping the engine full power, but on the other hand, 10 days early before starting replacing the mounts all was fine ,

only a Week early we motored the 70 miles plus through the Kiel canal speed was fine.
so I made the mistake of thinking it some thing to do with the mounts ,( engine miss Aline )
as I said the boat was out of the water in March while I worked on the rudder so I know the hull was clean,
one would not had thought I just 10 days enough fouling would build up slow the boat that much , well I wouldn’t thought so anyway other here have probably a degree in Barnacles

anyway problem now sorted , maybe I should had gone in the water sooner it save me posting here , on the other hand it may help other with speed if they not been in the water long and all the sudden after some time not moving they too have a problem .