MD2030 lost of speed

[sailaboutvic]

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 .

[team karst]

can engine make 3200 to 3800 in neutral and max throttle?

[sailaboutvic]

Originally Posted by team karst

can engine make 3200 to 3800 in neutral and max throttle?

It can do 3600 rpm in gear but speed is just touching 6 kts
I could get that at 2300 rpm before

[team karst]

Originally Posted by sailaboutvic

It can do 3600 rpm in gear but speed is just touching 6 kts
I could get that at 2300 rpm before

if its smooth, then I think transmission slipping.

[sailaboutvic]

Originally Posted by team karst

if its smooth, then I think transmission slipping.

As I understand it the MS15 as no clutch to slip .

[DougR]

First things first.......make sure the hull and especially the prop are absolutely clean, then retest.

Then, if still a problem, you can check the gear box for slipping. Of course the MS 15 has a clutch, two infact, one for forward and one for reverse. Probably the easiest way to check for slippage is to use a strobe tachometer. Check the crankshaft RPM when underway at high load/speed, and at the same time check the shaft rpm.

The shaft rpm should be about equal to the engine rpm divided by the gearbox reduction ratio.

[alamoana]

Is the tachometer RPM
Reading correct?

[team karst]

Originally Posted by sailaboutvic

As I understand it the MS15 as no clutch to slip .

I am pretty sure there are friction plates in there. How is reverse? I believe uses different discs.

[pesarsten]

I am curious as to how you aligned the shaft after replacing the mounts. Any change in engine height will have a marked impact on the effective pitch of the prop.

[sailaboutvic]

Originally Posted by DougR

First things first.......make sure the hull and especially the prop are absolutely clean, then retest.

Then, if still a problem, you can check the gear box for slipping. Of course the MS 15 has a clutch, two infact, one for forward and one for reverse. Probably the easiest way to check for slippage is to use a strobe tachometer. Check the crankshaft RPM when underway at high load/speed, and at the same time check the shaft rpm.

The shaft rpm should be about equal to the engine rpm divided by the gearbox reduction ratio.

Then prop clean as I been in to check and clean some of the bottom .
As for fouling , we are getting the same speed before under sail , there no noticeable difference , if it was fouling then I expect the problem would be more notice under sail .

I some how will have to get a strobe meter and check the shaft , we under way at the moment so it’s not easy to get my hand on any thing ,

So you say the shaft RPM a should be a equal of engine RPM divided by the gearbox ratio .
( ratio 2.14 .1 say at 2000 rpm I be looking at 233 Rpm on the shaft )?

[sailaboutvic]

Originally Posted by pesarsten

I am curious as to how you aligned the shaft after replacing the mounts. Any change in engine height will have a marked impact on the effective pitch of the prop.

I kept thinking this was the case but
I spoken to a couple of engineer and all say the engine aligned would have nothing to do with a lof of speed , if it was badly aligned the be vibration or even banging , I not getting any, and the difference in distance between couplings is 0.002 .

[sailaboutvic]

Originally Posted by team karst

I am pretty sure there are friction plates in there. How is reverse? I believe uses different discs.

Reverse is fine .

[sailaboutvic]

Originally Posted by alamoana

Is the tachometer RPM
Reading correct?

Yes there no reason to think it’s not .

[skipperpete]

If you see 233 rpm shaft speed at 2000 engine speed…. You have a lot of slippage. You should be seeing around 934 if the reduction is 2.14:1
Is the gearbox getting hot, or is the oil black and burnt smelling rather than atf red. Is this the same propeller as originally fitted and more importantly is the shaft turning opposite direction to engine rotation when in ahead, Volvo neglects to mention this in regard to the ZF Hurth transmission…. Those gearboxes are a trifle touchy about being run backwards.

[sailaboutvic]

Originally Posted by skipperpete

If you see 233 rpm shaft speed at 2000 engine speed…. You have a lot of slippage. You should be seeing around 934 if the reduction is 2.14:1
Is the gearbox getting hot, or is the oil black and burnt smelling rather than atf red. Is this the same propeller as originally fitted and more importantly is the shaft turning opposite direction to engine rotation when in ahead, Volvo neglects to mention this in regard to the ZF Hurth transmission…. Those gearboxes are a trifle touchy about being run backwards.

Sorry I did the calculations wrong your right it should be 934 , still need to find a way to check that .
No gearbox not getting hot ,
Oil clean so much it’s hard to see on the stick .
Prop been on for some years .
There no reason to think the shaft is running in the opposite then it run before the problem started nothing been done other then new engine mounts ,