Bavaria Ocean 38 MD22L - max engine temperature

[1simon]

Hi All,

So  today, after the new elbow was fitted, I motored out to check the engine, and  noted that engine temp was at 92C, at 1600Rpm. Speed was 4.5knts.

Keep in mind that I am sailing in the Med, where sea temp is around 25C and air temp around 27C.

The MD22L manual says that the operating max temp should be 90C, however I have also  downloaded an MD22L manual that states the the max engine temp should be 95C!

At 2000rpm, temperature reached 94C/95C and I reduced engine to 1000rpm, back to 91C.

The boat, a Bavaria Ocean 38 , is still new to  me and I am unsure what speed I should expect at 1500rpm, and what the max. temperature should be, however it appears to  be too hot and the speed slightly too low.

If anybody can shed any light I would appreciate it.

Simon

[Salty]

Could be a partial blockage within the sea water inlet pipework within the saildrive leg, a friend of mine was towed in with precisely that problem and a consequently overheating engine during the last week. Or it could be a partially blocked heat exchanger, did you check it before fitting the new exhaust seawater injection elbow? Also, do you know what temperatures were evident before you changed the elbow and at what revs?
Regarding speed, is your hull clean, as any fouling will slow you down considerably.

[1simon]

Hi,
Yes, I  forgot to  mention that the heat exchanger was checked when elbow was fitted.

I  will have engine checked again this week.

Temp. were in the same region prio rot  changing elbow,  but I would expect the temp to have improved now, which is why I am asking if this temp is normal after all.

[Yngmar]

That would depend on your propeller too. Mine is the original propeller that came with the boat: Fixed 3-blade aluminium alloy, Volvo (dia x pitch) 17 x 15 L Part No 21381279

My boat is almost the same (40 Ocean) with an MD22L-B and the above propeller and at 1600 rpm I get 6-6.5 knots, despite the boat being heavily loaded with a whole workshop and half a chandlery in spares ;-)

So yes, 4.5 knots seems slow unless you have a different (wrong) propeller. Or your bottom is massively fouled up.

I don't have an engine temperature gauge, just a warning light. I do know that even after long motoring, my exhaust does not get noticeably warm (I can put my hand on the hose coming off the elbow and it feels only very lightly warm - the heat exchanger top of course is hot). My manual says the engine temperature (coolant) gauge should be between 75 and 95°C, and around 90°C seems okay for a Diesel under load in warm climate.

So about the lack of thrust, first check what propeller you have, it may have been replaced with a wrongly sized one.

About the temperature, check coolant level, raw water output and exhaust temperature. If the exhaust water is really warm or not much of it is coming out of the exhaust, you probably have not enough flow through the heat exchanger. This could be missing impeller blades, blocked intake, saildrive leg channels (mine had mussels growing inside and restricting flow so much the exhaust was steaming when I bought the boat) or heat exchanger tube stack. Was the tube stack inspected/cleaned while you had the heat exchanger off?

It may also be that your engine thermostat is no longer working properly and not opening all the way - this is harder to diagnose though, although fairly easy (and not that costly) to replace.

[1simon]

Thanks for exhaustive reply!
Thermostat was changed this week  along with elbow etc.
I believe propellor is original , though I have to  check.
Will check re tube stacking, but should have been checked by engineer/mechanic, who  advised that he checked entire heat exchanger.
Bottom was cleaned 4 months ago  and was ok 2 weeks ago.

Will advise after more checks.

[Salty]

That would depend on your propeller too.........

That's interesting Yngmar, I'm curious and would appreciate any further info you may have regarding this point.
My previous boat, not a Bav, had been re-engined by the previous owner, but the original prop was retained which did not match the power output of the new engine. It used to overheat whenever I needed it to give a bit of grunt, and the engine was never able to run at maximum power output revs.

[Symphony]

really important to check propeller sizes when re-engining, particularly if replacing a 120 drive with a 130 as the reduction ratios are different. However the D1 engines run at 400 revs lower than the 20x0 engines, so the shaft revs are the same. The problem comes if you mix old engines with new drives or the other way round.

[Salty]

Yes, agreed as far as performance is concerned, but why would it make a difference to the temperature at which the engine runs?

[Yngmar]

Yes, agreed as far as performance is concerned, but why would it make a difference to the temperature at which the engine runs?

It doesn't (much). The propeller comment was about only achieving 4.5 knots at cruising rpm (which is ~1600 for my boat, which is nearly the same as Simon's boat).

Unless the propeller is severely oversized, but that's unlikely. More likely it's undersized and whirring away ineffectually.

Simon, you can check this - moor your boat up well, then put the engine in gear forward and open the throttle all the way. See what the max RPM is in that situation, compared to when in neutral. For mine it's 2000 rpm versus 3000 rpm. Keep in mind this is well different from opening throttle all the way with the boat moving. If it's much higher than 2000 rpm, your propeller is probably undersized.

Let us know what your propeller is.

[1simon]

Not sure I want to  try this- mooring and opening throttle to max....

Yngmar Quote "For mine it's 2000 rpm versus 3000 rpm". I am assuming that 3000rpm is at max throttle.  What is 2000rpm?

I cannot know the size of the propeller as boat is in the water,  but according to last Marine Survey it is a Volvo 3 blade aluminium propeller -  unfortunately I do  not have any more info, but I am assuming that it is the original.

[Yngmar]

Not sure I want to  try this- mooring and opening throttle to max....

Yngmar Quote "For mine it's 2000 rpm versus 3000 rpm". I am assuming that 3000rpm is at max throttle.  What is 2000rpm?

Don't worry, if you're moored stern to you won't pull the harbour wall down. 3k is max in neutral (as per spec) and 2k is in gear with the boat stationary. If your propeller is undersized, it'll go higher than that, because the smaller propeller slips more. Not a very scientific test, but much better than nothing.

[tiger79]

The MD22L manual says that the operating max temp should be 90C, however I have also  downloaded an MD22L manual that states the the max engine temp should be 95C!

The Instruction Book for the MD22L says that the temperature gauge should show 75-95C during normal operation.  The Technical Data for the MD22L says that the thermostat should be fully open at 92-98C.  In view of the fact that you're operating in warmish conditions, I don't see anything to worry about in the readings you're getting.

[1simon]

Hi Tiger 79,
Thanks for posting.
Sorry to  sound stupid - could you explain your comment that the thermostat is fully open at 92C to 98C?

[tiger79]

Hi Tiger 79,
Thanks for posting.
Sorry to  sound stupid - could you explain your comment that the thermostat is fully open at 92C to 98C?

The thermostat opens progressively, as the temperature rises.  It should start opening at 77-85C, and should be fully open by 92-98C.  I mentioned the fully open temperature range because it suggests that Volvo Penta don't consider that temperature excessive for the MD22L, whereas you were thinking that 90C was a max.

[1simon]

Tiger79, what happens once the thermostat opens fully at 92-98C?

[tiger79]

Tiger79, what happens once the thermostat opens fully at 92-98C?

The cooling system is running at its maximum ability.

[Kibo]

Think of the thermostat as a valve on the cooling water system. It opens a little when cooler to allow the engine to come up to normal operating temperature (range) and gradually opens more as the engine heats up hence allowing more cool fluid around the heat exchanger system. If the engine overheats first look at any possible blockages in the cooling system and raw water system, then take a look at the thermostat since that may stick or seize up and not open enough to allow the correct volume of coolant to circulate.

Hi Tiger 79,
Thanks for posting.
Sorry to  sound stupid - could you explain your comment that the thermostat is fully open at 92C to 98C?

The thermostat opens progressively, as the temperature rises.  It should start opening at 77-85C, and should be fully open by 92-98C.  I mentioned the fully open temperature range because it suggests that Volvo Penta don't consider that temperature excessive for the MD22L, whereas you were thinking that 90C was a max.

Hope that helps.

[sy_Anniina]

Trivial check - have you checked seawater filter?

Mine was not blocked, but the lid was a bit loose allowing air to bleed in the system, preventing efficient seawater cooling.

B40 - 2001, same engine as yours MD22L-B

[1simon]

Thanks for the comments , everyone.
I am having all checked by mechanic/engineer.

SY Annina - do  you  know if you get temp readings similar to mine at 1400 to 2000rpm?

[tiger79]

SY Annina - do  you  know if you get temp readings similar to mine at 1400 to 2000rpm?

If he's in Helsinki, and you're in the Med, possibly not!

[1simon]

Oh, did not know that.

[Salty]

On a slightly different tack from each of the foregoing comments, I've been reading through the manual for the MD 2020 engine on my B36(2002), and noted the following instructions, first under the following heading:-
Heat Exchanger. Cleaning
"Cooling performance is reduced by scaling in the heat exchanger. It should therefore be flushed when the coolant is exchanged.

Under
Coolant. Changing,
the manual stated
"The corrosion-proofing additives become less effective with time and the coolant must be changed. If the freshwater system is filled with antifreeze mixture it must be changed every other year (two years). If the system is filled with anti-corrosion agent mixture it must be changed every year.

This year shortly before bringing the boat ashore for the winter I looked more closely at the fresh water expansion tank which is located in the upper area on the aft bulkhead of the engine compartment near to the port side and where it is not at all easy to have a good close look at it without more contortions than my body was designed for. In the end I took off the black plastic filler cap on that tank, and stuck my fingers into what I thought would be water, but which turned out to be a mass of brown crud which fortunately is not connected to the toilet waste system !!  How anything actually flowed through that expansion tank is a mystery, but it got me thinking that I'd not changed the cooling water ever, and I'm guessing the previous owner didn't, so it was likely that the cooling waterways might also be partially blocked with similar crud.
I couldn't see the liquid level in the expansion tank, so took it off last weekend and brought it home where I've managed to clean and remove at least 99% of the crud using initially some thin bleach left on an overnight soaking (not very successful) and then some Lime Scale Dissolver from the first mates cupboard full of useful liquid cleaning products. It worked like a dream and I can now see the liquid level within that tank. The coolant drain valve on the starboard side of the engine is just a screwed in plug on mine, so that will be released next time onboard and the system flushed through with water.
So the question is, if your engine is getting warmer than you think it should, have you changed the coolant at the recommended frequency of every one or two years depending on exactly what it is that you have in your fresh water system ? 
Oh well, it's nice to know I'm not the only one who didn't think about it !!