MD 2030 follow up

[sailaboutvic]

Has some may know I changed my engine mount the other week .
bit of a pain but the job got sorted .
since then we moved twice .
before the mounts was replaces , at 1800/2000RPM we had a speed around 5.5 to 6 kts , we now seen to have around a knot less .
( speed taken from GPS not the log )
im sure it’s not my imagination ,
could this have anything with the engine line in up with the shaft.
there no vibration to speak off.
shaft turn by hand no restrictions.
the shaft and engine coupling seen to line up fine , probably 0.002 different if any from top to bottom .
I can’t see why it should make any difference but worth asking .
thank for any suggestions.

 

[penfold]

If you're doing the same engine rpm the speed should be the same. The shaft rpm could be checked with a handheld tachometer to see if there is clutch slip. Any chance you've collected some floating debris around the keel or rudder and causing drag?

 

[westernman]

A small amount of fouling on the prop?
To my surprise, I found that a couple of barnacles on the prop could easily make 1.5 knots different at full throttle.

 

[Tranona]

That sounds a high speed for a 2030 at those revs in a boat like yours. Much the same as as my old Bav 37 in size and displacement. 5.5 knots at 2300.

GPS is speed over ground not through the water and only the same with no tide/current. Adverse wind will also affect speed through water. Only way to check is to do test runs in both directions in flat water with no current at, say 200rpm intervals from 2000 up to maximum which shouls be minimum 3300rpm.

 

[sailaboutvic]

Don’t have a

If you're doing the same engine rpm the speed should be the same. The shaft rpm could be checked with a handheld tachometer to see if there is clutch slip. Any chance you've collected some floating debris around the keel or rudder and causing drag?

don’t have a tachometer so that out .
we done about 100 miles in the last two trip mostly under sail so I guess if by any chance there was some floating debris I would had expect it to fall off .

 

[Tranona]

Then the basic check as to whether the propeller is correct - no reason why it should not be is to run up to maximum and you should get a speed of 7.4 knots+. If that is OK then the cruising speed/revs would be similar to that I suggested. You really need a tacho rather than guessing.

 

[sailaboutvic]

That sounds a high speed for a 2030 at those revs in a boat like yours. Much the same as as my old Bav 37 in size and displacement. 5.5 knots at 2300.

GPS is speed over ground not through the water and only the same with no tide/current. Adverse wind will also affect speed through water. Only way to check is to do test runs in both directions in flat water with no current at, say 200rpm intervals from 2000 up to maximum which shouls be minimum 3300rpm.

Hi T
we could motor at 1800/2000 rpm @ 5 Knots no problem with a small current agains us ,
I doubts there much current here in the Baltic where we are at the moment , hardly anything showing on buoys / stages piles or if I throw anything over board .
Log and and gps almost the same .
my concern at the moment if and it’s a big IF the shaft and engine is still out of line, although as said no vibration.

although I checked it several times and although it’s not 100% with feel gauges it no more then 0,002 from one side to the other if That .

 

[penfold]

Deleted

 

[sailaboutvic]

delete

 

[sailaboutvic]

Then the basic check as to whether the propeller is correct - no reason why it should not be is to run up to maximum and you should get a speed of 7.4 knots+. If that is OK then the cruising speed/revs would be similar to that I suggested. You really need a tacho rather than guessing.

The RPM I have quto is taken from the boat revolution-counter,
when I said I don’t have a tacho to pendold I meant external instrument.

 

[Tranona]

The boat's rev counter is pretty accurate. No need for an independent one. 5 knots at 2000 is about right - up 2-300 will give you the next 0.5 knots. It is the last bit from 6.5 upwards that needs a disproportionate amount of power and revs.

Can't see how the replacement of mounts could make any difference to performance.

 

[david_bagshaw]

Perhaps during the installation of the new bits, maybe ,
1 pinched a fuel pipe
2 altered the throttle control cables or full throttle not being achieved.
3 pinched exhaust pipe.

 

[sailaboutvic]

Can't see how the replacement of mounts could make any difference to performance.

Non can I which is why I asked the question in case I’m missing some thing .

never lined up an engine before I just wonder if it wasn’t 100% right could it effect drag on the shaft speed .
although as said no vibration to talk about , and if anything only 0.002 out from one side to other between couplings.

I always found when a problem arise after work took place is
to look at the last thing that’s been done .

I now will have to look else where ,
I can imagine the 10 days the boat didn’t move it fouled up enough to couse that lost of speed ,
plus the average speed / distance we covered under sail the last two day (105 nm under sail ) is comparison with what it did before , which tells me fouling isn’t the problem .
time for a dip just to check .

 

[sailaboutvic]

Perhaps during the installation of the new bits, maybe ,
1 pinched a fuel pipe
2 altered the throttle control cables or full throttle not being achieved.
3 pinched exhaust pipe.

thanks David but I would had notice tho problem in the way the engine was running .
engine running fine .

 

[sailaboutvic]

Following from my last post when I said I needed to take a dip ,
To my surprise I found the back end had micro barnacles quite a lot.
Just from the back of the keel ,
forward of that there wasn’t any .

I’m not idea how quickly these buggies latch onto a hull but I wouldn’t thought that quickly .

It seen the 10 day in the marina while working on the boat and helping out at a wedding the growth must had appeared .
I say this as before then I had no problem with speed .
I not manage to clear them all as there a strong current running and I’m not a strong swimmer ,
but the amount I have cleared as added a good knot on my speed under engine .
As soon as we anchor in a better place o will finish the job.

I can only guess the CC isn’t working on the back as the front .

(Wipe my brow) relieve I just got it into my head it had some thing todo with the mounts I changed and was about to redo the whole job.



Thanks everyone for the suggestion.

 

[westernman]

Following from my last post when I said I needed to take a dip ,
To my surprise I found the back end had micro barnacles quite a lot.
Just from the back of the keel ,
forward of that there wasn’t any .

I’m not idea how quickly these buggies latch onto a hull but I wouldn’t thought that quickly .

It seen the 10 day in the marina while working on the boat and helping out at a wedding the growth must had appeared .
I say this as before then I had no problem with speed .
I not manage to clear them all as there a strong current running and I’m not a strong swimmer ,
but the amount I have cleared as added a good knot on my speed under engine .
As soon as we anchor in a better place o will finish the job.

I can only guess the CC isn’t working on the back as the front .

(Wipe my brow) relieve I just got it into my head it had some thing todo with the mounts I changed and was about to redo the whole job.



Thanks everyone for the suggestion.

Told you so. Post #3.

 

[sailaboutvic]

Told you so. Post #3.

Yes you did but to be honst the boat was out of the water in march as I was replacing the rudder bearing ,
and Iwould had laid money the bottom was still clean .
plus the difference in speed happened in such short time , 10 days while the boat didn’t move .

 

[sailaboutvic]

A quick read up just out off interested .
barnacles can attach within two weeks of being in the water ,
the danish must have super barnacles as it was only in the marina not moving for 10 days.

 

[ChromeDome]

Wind and current the same during speed tests?

 

[LittleSister]

Perhaps during the installation of the new bits, maybe ,
1 pinched a fuel pipe
2 altered the throttle control cables or full throttle not being achieved.
3 pinched exhaust pipe.

The OP has solved his issue now I believe, but none of those suggestions could have caused the problem he reported, i.e. lower boat speed at same engine revs.

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