Bukh 36 - experiences?

[MtB]

14 minutes ago, Michael Siggers said:

So plan is;

1. Check actual engine speed and see how accurate the Tacho is
2. Measure the Prop as best as I can through the weedhatch,
3. Find Gearbox reduction Ratio

 

The pitch of the prop is just as important as the diameter, and I don't see how you can determine that down the weed hatch. Its probably stamped on the boss somewhere but those markings are hard enough to find with the prop on the bench with a good light! 

 

 

[Michael Siggers]

1 minute ago, MtB said:

The pitch of the prop is just as important as the diameter, and I don't see how you can determine that down the weed hatch. Its probably stamped on the boss somewhere but those markings are hard enough to find with the prop on the bench with a good light!

Yes, I appreciate that. Thought the Diameter is a good start. It is out of the water for Blacking soon so will try and find the stamped mark too.

[Tony Brooks]

12 minutes ago, Michael Siggers said:

One arriving tomorrow.

 

So plan is;

1. Check actual engine speed and see how accurate the Tacho is
2. Measure the Prop as best as I can through the weedhatch,
3. Find Gearbox reduction Ratio

Long conversation with TW Marine, who were very helpful, and I can get the above information to him. Then form a plan of what to do.

 

Do seem to get some mixed messages though in terms of, some people say they have over propped and its ok as it reduces the revs etc, and TW Marine saying it's no good for the engine. On the post I created before, one person said they had deliberately added a larger prop to reduce the engine revs and it suited them for the Canals. TW Marine say the engine should go to over 3000 RPM when in gear, but this seems like it would be 'screaming'. Even say, 2500RPM when cruising would seem 'excessive/noisy' etc.

 

Mike

But at 1500 RPM, it is flying along, probably too fast.

 

At least with the big flywheel, you can manually turn the engine through one revolution in gear and see how much the shaft turns.

 

I am not sure how you will find the prop pitch through the weed hatch, and as the diameter tends to be limited by the hull design if anything s wrong it more likely to be pitch.

 

After fitting a Cowthers recommended prop the revs would never go to 3000, even on the Severn, Trent and Thames it never went above about 2500 rpm.

 

I don't think a degree of over propping will harm the engine as long as you stop moving the throttle once the revs stop rising. Certainly stop and pull back a tad the moment it starts making black smoke.

 

[Michael Siggers]

1 minute ago, Tony Brooks said:

At least with the big flywheel, you can manually turn the engine through one revolution in gear and see how much the shaft turns.

Thank you @Tony Brooks

 

Bloody good idea! As much information as I can gather is good, so will do that as well. Assuming I put the engine in gear using the lever even though it is not running?

 

That Prop sounds interesting. Would you happen to have the details to hand so that I can compare once I have all the information on my Prop?

 

Mike

[Tony Brooks]

6 minutes ago, Michael Siggers said:

This is making sense now. (I've been having a slow day  )

 

Trying to find someone experienced with these engines near me is proving difficult.

 

Mike

 

I am not sure what is so special about the engine. The fuel system is standard Bosch such as fitted in Ford Transits etc. Pretty standard marine cooling system. The only "odd" thing is the internal balance weights that no-one should get near, apart from during overhaul.

 

I suppose a run-of-the-mill engineer may expect a gearbox drive plate rather than the metal fingers and rubber intermediate disk, but once you see it, it is obvious what is going n.

[David Mack]

9 minutes ago, MtB said:

Its probably stamped on the boss somewhere but those markings are hard enough to find with the prop on the bench with a good light! 

 

7 minutes ago, Michael Siggers said:

It is out of the water for Blacking soon so will try and find the stamped mark too.

Problem is that sometimes the prop size stamping is on the end of the prop boss, so when fitted to the boat it can be covered by the nut which holds the prop onto the shaft.

[Alan de Enfield]

Bukh parts & servicing "experts"

 

Bukh Marine Engine Service Parts & Spares — T.Norris Marine (tnorrismarine.co.uk)

[Tony Brooks]

2 minutes ago, Michael Siggers said:

Thank you @Tony Brooks

 

Bloody good idea! As much information as I can gather is good, so will do that as well. Assuming I put the engine in gear using the lever even though it is not running?

 

That Prop sounds interesting. Would you happen to have the details to hand so that I can compare once I have all the information on my Prop?

 

Mike

 

1. Yes

 

2. No, invoice handed to the boat's new owner.

 

There are online prop calculators (Vicprop) that will give you a rough idea of what prop you need.

3 minutes ago, Tony Brooks said:

 

I am not sure what is so special about the engine. The fuel system is standard Bosch such as fitted in Ford Transits etc. Pretty standard marine cooling system. The only "odd" thing is the internal balance weights that no-one should get near, apart from during overhaul.

 

I suppose a run-of-the-mill engineer may expect a gearbox drive plate rather than the metal fingers and rubber intermediate disk, but once you see it, it is obvious what is going n.

 

To add, setting the valve clearances is a bit different to four-cylinder engines but the same as single cylinders. One valve fully down - mark flywheel - turn flywheel one complete turn (more or less)- adjust that valve. Move onto the next one.

[MtB]

1 minute ago, David Mack said:

 

Problem is that sometimes the prop size stamping is on the end of the prop boss, so when fitted to the boat it can be covered by the nut which holds the prop onto the shaft.

 

 

Ok another approach would be to embed the prop in that large, fixed, apocryphal block of cheese. Then rotate the prop shaft exactly one revolution and measure how far the boat moves. This will be equal to the pitch of the prop.

 

And I haven't even had any BEER yet!!!

 

 

 

 

[Tony Brooks]

Just noticed that in this topic during 2016 I said I thought the prop was 14" pitch 16" dimeter - but note the word THOUGHT.

[IanD]

10 minutes ago, MtB said:

 

Ok another approach would be to embed the prop in that large, fixed, apocryphal block of cheese. Then rotate the prop shaft exactly one revolution and measure how far the boat moves. This will be equal to the pitch of the prop.

 

And I haven't even had any BEER yet!!!

 

 

You can also work it out by measuring the angle and radius of the blades at their widest point...

[MtB]

4 hours ago, IanD said:

 

You can also work it out by measuring the angle and radius of the blades at their widest point...

 

No I can't...  not after this much cider! 

 

 

[Peugeot 106]

I know i’ve come to this very late but my boat is overpropped and works very well. If you run it in gear max revs are around 2200 rpm. But if run out of gear it runs at 3000 rpm (which is the maximum for the engine). With yours I would expect 3500 rpm out of gear. Simple check I assume you have tried it?

[IanD]

4 minutes ago, Peugeot 106 said:

I know i’ve come to this very late but my boat is overpropped and works very well. If you run it in gear max revs are around 2200 rpm. But if run out of gear it runs at 3000 rpm (which is the maximum for the engine). With yours I would expect 3500 rpm out of gear. Simple check I assume you have tried it?

2200rpm flat out for an engine rated at 3000rpm is not so bad, with a typical torque curve that's reaching more than 80% of full power -- 20% drop in exchange for lower rpm and less noise and wash is a good deal, and will only knock about 6% off maximum boat speed in deep water/rivers, which is really the only time you're likely to run flat out.

 

1500rpm flat out for an engine rated at 3600rpm -- if those figures are correct! -- is heavily overpropped, this will only give about 50% of full power and will knock about 20% off maximum boat speed. If this is OK (and minimum speed at tickover isn't too high, or rpm too low for the engine) then that's fine, but you might as well have an engine half as big!

 

The low rpm may also mean alternator battery charging is not very good, but that's a separate problem... 😉

[Peugeot 106]

17 minutes ago, IanD said:

2200rpm flat out for an engine rated at 3000rpm is not so bad, with a typical torque curve that's reaching more than 80% of full power -- 20% drop in exchange for lower rpm and less noise and wash is a good deal, and will only knock about 6% off maximum boat speed in deep water/rivers, which is really the only time you're likely to run flat out.

 

1500rpm flat out for an engine rated at 3600rpm -- if those figures are correct! -- is heavily overpropped, this will only give about 50% of full power and will knock about 20% off maximum boat speed. If this is OK (and minimum speed at tickover isn't too high, or rpm too low for the engine) then that's fine, but you might as well have an engine half as big!

 

The low rpm may also mean alternator battery charging is not very good, but that's a separate problem... 😉

I’d agree with all that (which is why I like being overpropped). I guess you also need a few revs to distribute the lube oil. I am just suggesting as a quick check if he can’t get 3600rpm out of gear there may be a problem

[Slim]

16 hours ago, Alan de Enfield said:

 

They were used in Lifeboats so maybe try and find a service centre on the coast (maybe Aberdeen, or Lowestoft) where these life boats are tested.

I know a number of Rival 38s were fitted with the engine. Perhaps looking to the offshore forums would help. (Updated Practical Boat Owner )

[Michael Siggers]

On 30/01/2024 at 09:54, IanD said:

2200rpm flat out for an engine rated at 3000rpm is not so bad, with a typical torque curve that's reaching more than 80% of full power -- 20% drop in exchange for lower rpm and less noise and wash is a good deal, and will only knock about 6% off maximum boat speed in deep water/rivers, which is really the only time you're likely to run flat out.

 

1500rpm flat out for an engine rated at 3600rpm -- if those figures are correct! -- is heavily overpropped, this will only give about 50% of full power and will knock about 20% off maximum boat speed. If this is OK (and minimum speed at tickover isn't too high, or rpm too low for the engine) then that's fine, but you might as well have an engine half as big!

 

The low rpm may also mean alternator battery charging is not very good, but that's a separate problem... 😉

An update on the RPM.

 

Further investigation revealed that the Tacho was out and under reporting the revs. I have been chatting alot with TW Marine, who have been phenomenally helpful. It turns out Nick at TW Marine actually fitted the engine in my boat when it was built and remembers it well. I've offered to buy him so he can live in my engine bay 😀. Many detailed conversations about boat design, water depth, prop design etc etc etc.

 

They have been brilliant and have helped me recalibrate the Tacho. I have also now confirmed the actual engine speed and the actual prop speed. This all points to over propping and when the boat is out of the water for blacking I'm going to get the details of the prop. They did mention about the performance of the Alternator too, in relation to over propping.

 

In terms of speed in the water, the boat shifts. If I increase to around 1100 - 1200 rpm, it's flying! Again, this leads me to think, and be pretty sure following conversations with TW Marine that it's been over propped. For the record, it was not TW Marine that over propped it.

 

Anyway, engine has also been serviced and TW Marine are also helping me replace the Tiller Bearing.

 

I can not praise them highly enough. They have given me so much of their time and I have learnt so much from them.

 

Mike

[Peugeot 106]

9 hours ago, Michael Siggers said:

An update on the RPM.

 

Further investigation revealed that the Tacho was out and under reporting the revs. I have been chatting alot with TW Marine, who have been phenomenally helpful. It turns out Nick at TW Marine actually fitted the engine in my boat when it was built and remembers it well. I've offered to buy him so he can live in my engine bay 😀. Many detailed conversations about boat design, water depth, prop design etc etc etc.

 

They have been brilliant and have helped me recalibrate the Tacho. I have also now confirmed the actual engine speed and the actual prop speed. This all points to over propping and when the boat is out of the water for blacking I'm going to get the details of the prop. They did mention about the performance of the Alternator too, in relation to over propping.

 

In terms of speed in the water, the boat shifts. If I increase to around 1100 - 1200 rpm, it's flying! Again, this leads me to think, and be pretty sure following conversations with TW Marine that it's been over propped. For the record, it was not TW Marine that over propped it.

 

Anyway, engine has also been serviced and TW Marine are also helping me replace the Tiller Bearing.

 

I can not praise them highly enough. They have given me so much of their time and I have learnt so much from them.

 

Mike

The prop can be repitched within reason by a propellor refurbisher if this is the way you want to go. It may well be worth speaking with a manufacturer/ refurbisher now so that you can get an idea of what they have, what prop size they think is applicable to your boat  and what they can do. When you do get it out of the water if all your ducks are in a row you may get a very quick turnaround.

i don’t know what your new tacho readings are but a fair few of us are happy with a degree of overpropping. In my case my engine will get to 3000 rpm out of gear but in gear 2200 is the max

It is reassuring to get advice off Norris but all I’m saying is make sure you know of all your options before you come out for blacking 

Thanks for reporting back

[Tony Brooks]

39 minutes ago, Peugeot 106 said:

i don’t know what your new tacho readings are but a fair few of us are happy with a degree of overpropping. In my case my engine will get to 3000 rpm out of gear but in gear 2200 is the max

 

I agree with that. As long as you stop trying to accelerate when the revs top out and then back off a tad.

[Michael Siggers]

2 minutes ago, Tony Brooks said:

 

I agree with that. As long as you stop trying to accelerate when the revs top out and then back off a tad.

Yes, I never need to go max out.

 

I am looking at the option of changing the prop once I have established what I have actually got on it at the moment.

 

Mike

[David Mack]

2 hours ago, Peugeot 106 said:

It may well be worth speaking with a manufacturer/ refurbisher now so that you can get an idea of what they have, what prop size they think is applicable to your boat  and what they can do.

Just be aware that most prop companies are not interested in being a free design service. So while they will engage to a degree, they won't tell you what size prop they recommend until you have handed over some money.

[Peugeot 106]

1 hour ago, David Mack said:

Just be aware that most prop companies are not interested in being a free design service. So while they will engage to a degree, they won't tell you what size prop they recommend until you have handed over some money.

When Crowthers closed  they recommended me to another company the trouble is i  can’t remember who. They did a prop sizing and said they could alter my pitch or supply a new one but talked me out of it explaining that I wouldn’t go any faster with a new prop. A smaller prop turning fast does much the same as a larger prop turning slower ( within reason) they said that engine installers don’t like overpropped boats and won’t guarantee them as people can damage them ( especially hirees) if they keep pushing the throttle open after top revs have been attained

They were of the opinion that reasonable  overpropping was of benefit  in some respects if the throttle operator knew about not over throttling. 
At the end of the day it’s the speed your hull will reasonably achieve which is not necessarily theoretical hull speed if you’ve got a bluff bow, short swims, shallow water etc.

BUT you don’t want to go to fast in idle 

 

Maybe somebody on the forum can tell you who was recommended by Crowthers. They told me what prop I could go for and also gave me good reason not to bother. 
When you talk to people about RPM make sure you distinguish between engine and propellor RPM. Most gearboxes are 2:1, 2.5:1 or 3:1 I believe so there can be a big difference. The ratio should be on the gearbox nameplate and is normally different for forward and reverse. ( the propellor goes slower than the engine!)

 

sorry if I’m being long winded but I have thought I had similar problems to you. I am an enthusiastic amateur though and not an expert

 

good luck

[David Mack]

3 hours ago, Peugeot 106 said:

Maybe somebody on the forum can tell you who was recommended by Crowthers.

Clements Engineering?

[MtB]

3 hours ago, Peugeot 106 said:

When Crowthers closed  they recommended me to another company the trouble is i  can’t remember who.

 

I think it was Michigan. 

 

Michigan Marine Propulsion

 

https://mmp-i.com/

 

 

 

[ditchcrawler]

8 minutes ago, David Mack said:

Clements Engineering?

The boat moored almost next to us has used them and was more than happy, Nothing to do with Narrowboats but I think they do work for the RNLI