Engine working well in forwards but losing power in reverse

[samsuka]

Hi,

We have a Westerly Falcon 34 with a new Yanmar 30hp diesel engine (2020). We bought it in the Autumn last year and the engine has been great, however when we went down last weekend to have a bit of a pootle about we found that the engine was working fine in forwards, but seemed to have lost power in reverse, when in full reverse you can feel that its not working as hard as it normally does, so it was a bit of an issue getting in and out of the marina. Any ideas? We did the normal checks and seemed OK.

Thanks

 

[Concerto]

Sounds like the reverse cable needs adjusting as it is not fully engaging.

You can do this yourself and whilst tied up in your marina berth.

 

[rotrax]

The propeller, of course, is not so efficient in reverse.

Test what RPM the engine will reach in both ahead and astern.

If there is a significant difference the prop might be fouled.

It does not take much.

 

[Pye_End]

Gearbox ratio may well be higher in reverse so if there is any prop fouling it may be more noticeable.

 

[peteK]

If its been sitting in a marina probably fouled with weed.

 

[johnalison]

It might be the folding prop isn't opening properly, as well as being foul. Blade pressure will assist it in opening when ahead but when going astern it only relies on centrifugal force (with apologies to physicists). Mine opens with a clonk when forwards is engaged and if I don't hear this I know that it is foul.

 

[Aeolus]

When something similar happened to me, I discovered some ropes round the prop that didn't cause much of a problem going forward but severely hampered reverse.

 

[samsuka]

Ahaha, ok yes that makes the most sense. Will need to get my wetsuit out it seems!!

 

[earlybird]

Friend of mine had this problem with a newly purchased boat. When lifted and the prop examined it turned out that there was no key to the shaft. Prop thrust was causing the taper to lock when in forward gear but allowing it to slip when in astern gear.Perhaps a rather unusual fault.
If the OPs prop is a folder, I'd definitely go for not opening properly in astern.

 

[Pye_End]

Ahaha, ok yes that makes the most sense. Will need to get my wetsuit out it seems!!

Waterproof camera on a boat hook regularly handy.

 

[samsuka]

Actually thinking about it more the RPM is definetly lower when its in reverse, so i think it may be something else, but the waterproof camera on a boat hook makes a lot of sense. Thanks

 

[CapPugwash]

My Yanmar 3HMF 27-HP developed a similar problem when we launched last season. She would stall when reversing unless I gave it some welly. I put it down to my Kiwi Prop not switching without some oomf. However, when we lifted out at the end of the season it seemed fine. My current theory is that propeller shaft bracket tube needs replacing. Mine is supported by a bracket with a tube for the propeller shaft to go through. I forget the correct term, sorry. I saw a chap on YouTube replace his in the Caribbean which made me think it might be the problem for me.

 

[Tranona]

If you have a standard Yanmar gearbox the reverse ratio is greater than the forward. This means that it will not achieve the same sort of revs as in forward, but at low speed it gives you more stopping power and speed at low revs. You don't say what you mean by "lost power" - is the boat not moving as quickly as you think it should, or not revving easily? The engine has more than enough power for the boat so any problem is likely to be connected with the prop and a fouled prop is the most obvious.

 

[samsuka]

If you have a standard Yanmar gearbox the reverse ratio is greater than the forward. This means that it will not achieve the same sort of revs as in forward, but at low speed it gives you more stopping power and speed at low revs. You don't say what you mean by "lost power" - is the boat not moving as quickly as you think it should, or not revving easily? The engine has more than enough power for the boat so any problem is likely to be connected with the prop and a fouled prop is the most obvious.

It was definetly not revving as much in reverse compared to previously. One of the guys from the marina got on board to try it out and said the same. Definetly some sort of issue.

 

[rotrax]

The Kiwi Prop info makes it clear the pitch is too coarse in reverse, so stopping full RPM from the engine.

In my direct experience of this most excellent product, this is the only drawback.

 

[PabloPicasso]

Actually thinking about it more the RPM is definetly lower when its in reverse, so i think it may be something else, but the waterproof camera on a boat hook makes a lot of sense. Thanks

I bought a Bluetooth endoscope. It has a camera on a long wire and the image can be viewed on phone.

 

[ddhx]

Hi,

We have a Westerly Falcon 34 with a new Yanmar 30hp diesel engine (2020). We bought it in the Autumn last year and the engine has been great, however when we went down last weekend to have a bit of a pootle about we found that the engine was working fine in forwards, but seemed to have lost power in reverse, when in full reverse you can feel that its not working as hard as it normally does, so it was a bit of an issue getting in and out of the marina. Any ideas? We did the normal checks and seemed OK.

Thanks

Hi,
Sorry, I've no idea about your problem ... but I'd like to know how maneuverable is the westerly falcon when reversing with the engine please?
Thanks a lot,
DH

 

[jamie N]

Hi DH. Welcome to the forum. It'd be an idea to start a new thread to get a better response I reckon.

 

[ddhx]

Yes, good idea
DH