New engine - Gearbox and panel questions...?

[Boo2]

Hi,

I am defo planning to re-engine Sunrunner (UFO 34) this summer. I am keeping options open regarding the choice between Yanmar, Beta and Nanni but I also need to decide what gearbox and switch panel to fit.

Can anyone give me the executive precis of the differences between hydraulic and mechanical gearboxes and which is preferable ? I see Beta come with the option of PRM gearboxes which is what is rusting at the end of Sunrunner's propshaft (see pix below), should I be glad to get away from them or determined to get another ?

Also, Sunrunner, like most, has an angled propshaft (don't know the exact angle) but AFAICT the bearers are parallel with the waterline, presumeably I need an angled gearbox ? How can I tell what will work without actually trial fitting an engine ?

In respect of getting that coupling to let go does ybw cognoscenti reckon Plusgas will be enough or should I fork out for an angle grinder now ?


Finally, ISTM a keyswitch is irrelevant on a boat and unsuited to the marine environment to boot so I am planning a button and dials only panel. Is this a mistake ? Has anyone here done that and regretted it ? Where can I get a reasonabley priced button and dials only panel ? (I don't think all the engine manufacturers offer one).

Thanks,

Boo2

 

[Tranona]

betas and Nannis come with a TMC gearbox as standard for in line installation or Kanzaki for down angle. These gearboxes are perfectly adequate and widely used. Yanmar use their own gearboxes as do Volvo. There is a choice of reduction ratio which will be determined by the size of prop you can swing. You can do your own calculations using the Propcalc programme on www.castlemarine.co.uk but your supplier will give you a recommendation. Does not look like your current gearbox is down angle. There are alternative ways of getting a down angle such as an Aquadrive if you need it. Getting the old coupling off might be tough and if you are changing the shaft you might just use your angle grinder!

With regard to panels, not sure anybody does a button only one. I have one on my Volvo 2030 but I think they now use keys. The panels are electronic and programmed for the engine, including a solenoid operated stop. Not sure I would want to try and build one rather than use the manufacturers panel.

 

[earlybird]

A couple of points, Beta do a button only panel, which they refer to as waterproof. This is an optional extra.
As Tranona says, your gearbox doesn't look angled, but perhaps photo is deceptive. If you do need one, that would require accurate measurement, and extra cost.
An advantage of an hydraulic box is that it is rated at full power in both directions, which you don't need in a sailboat.
Mechanical boxes are usually de-rated by a big factor for reverse rotation.
Re Aquadrives, IIRC, they are specified for 7 deg. max. and are de-rated at that, but I can't recall the figures.
It would also add several hundred £'s and more installation costs.

 

[prv]

Yanmar use their own gearboxes as do Volvo.

That must be a new thing, then, as I'm pretty sure the one on the back of my 2GM20 is a Kanzaki.

With regard to panels, not sure anybody does a button only one. I have one on my Volvo 2030 but I think they now use keys. The panels are electronic and programmed for the engine, including a solenoid operated stop.

That's sad to hear - can't see any good reason for the panel on a simple engine like this to be electronic or programmable. The old kind was just a bundle of wires between the individual parts, very easy to cannibalise into a new panel as I did, with a rotary switch instead of the key.

A quick look at the Yanmar web site to see what the new panels look like reveals that they do do a keyless one with just buttons. Maybe other manufacturers do too?

I guess talk to Beta about your requirements, they're well known for doing custom work for re-engine projects, and that may extend to a modified panel.

Pete

 

[Tranona]

A couple of points, Beta do a button only panel, which they refer to as waterproof. This is an optional extra.

Missed that on the extras list - guess because when I was buying that was not something I needed. The panel that came with my Nanni 14 is key operated and is a universal panel for all the small engines. There is a setup routine unique to each model to set the rev counter and hour meter.

 

[Plevier]

use their own gearboxes as do Volvo.

Volvo gearboxes (including saildrive) are made by ZF (formerly Hurth, taken over by ZF). They appear identical to the ones offered by ZF under their own name but I can't state that definitively.

 

[Boo2]

betas and Nannis come with a TMC gearbox as standard for in line installation or Kanzaki for down angle. These gearboxes are perfectly adequate and widely used.

Thanks to all who replied on this thread. Nanni (ie Peachment) have also said they can supply a button-only waterproof panel, so if the TTMC35 gearboxes are OK then Nanni are still in the running.

A further question regarding gearboxes, Sunrunner currently has a hydraulic gb (I think is's a PRM100) and this will let the prop rotate with the engine off unless it is stopped whilst still in gear. Is this generally a property of hydraulic gearboxes ? It's a bit of a pain to switch off then hear the prop rumbling and have to switch back on again, put in gear and switch off. If all hydraulic boxes are like that then I would prefer a mechanical box.

Thanks,

Boo2

 

[sailorman]

Thanks to all who replied on this thread. Nanni (ie Peachment) have also said they can supply a button-only waterproof panel, so if the TTMC35 gearboxes are OK then Nanni are still in the running.

A further question regarding gearboxes, Sunrunner currently has a hydraulic gb (I think is's a PRM100) and this will let the prop rotate with the engine off unless it is stopped whilst still in gear. Is this generally a property of hydraulic gearboxes ? It's a bit of a pain to switch off then hear the prop rumbling and have to switch back on again, put in gear and switch off. If all hydraulic boxes are like that then I would prefer a mechanical box.

Thanks,

Boo2

yes it is.
the hyd box is more robust,less noise too.
i have a PRM 150 + a MaxProp so no spinning shaft

PRM = Percy Riley Motors.
remember Riley Motors

 

[richardm47]

I chose a button-only panel to go with my new Beta, mainly because someone leant against the key in the previous Volvo panel and broke it off. Half was left in the key hole, no easy way to start the engine. On-passage key hole surgery followed!

I don't regret choosing buttons at all, would definitely do so again. More robust, less likely to corrode, no key to loose.

One tip: although the buttons on the Beta panel look well protected inside rubber hoods, they can still be pushed by a crewman that leans heavily against them. Not a huge problem, I will probably inset the whole panel this winter, but you can allow for it in your design. May not be an issue for you, depending on location of the panel.

With the Beta buttons panel, you get an over-temp buzzer/light warning but not an actual temperature dial.

 

[Tranona]

Thanks to all who replied on this thread. Nanni (ie Peachment) have also said they can supply a button-only waterproof panel, so if the TTMC35 gearboxes are OK then Nanni are still in the running.

A further question regarding gearboxes, Sunrunner currently has a hydraulic gb (I think is's a PRM100) and this will let the prop rotate with the engine off unless it is stopped whilst still in gear. Is this generally a property of hydraulic gearboxes ? It's a bit of a pain to switch off then hear the prop rumbling and have to switch back on again, put in gear and switch off. If all hydraulic boxes are like that then I would prefer a mechanical box.

Thanks,

Boo2

If you are going to all this trouble to fit a new engine, best to specifiy a folding prop, then your problem of whether to lock or spin the prop goes away. The incremental cost of a two blade FlexoFold over a fixed prop, given you will need a new prop anyway is very small in relation to the overall spend. You will appreciate your wise decision for all the time you have the boat.

You can tie yourself up in knots trying to decide which engine to have, but at the end of the day, the boat does not care. It just needs the hp and an appropriate shaft speed to swing an efficient prop. Going the extra bit and having a folding prop will ensure you have efficient propulsion and minimise drag in light airs.

So, work back from the biggest two blade folder you can swing, given that you can't easily change your P bracket - remember you need ideally 15% diameter clearance from the blade tips and specify your gearbox ratio and engine hp to swing the prop.

For your engine beds, if you have standard Thorneycroft engine mounts then I expect Beta and Peachment will have the dimensions to fabricate brackets to fit your new engine. If not, mock up the key engine dimensions using a 1" broom handle as a propshaft and build up your existing beds to meet the mounting feet of the new engine. There is more than enough adjustment on each mount to take up any minor discrepancies - the key thing is to get the beds at roughly the right height and aligned with the shaft.

 

[Tranona]

Just to add a little bit, having done some calculations. Not sure you need a 35hp. You may not have enough room to swing a big enough prop - you need at least 18" diameter 2 blade to absorb the power. The weight and speed potential of your boat does not justify 35hp and suspect they were only fitted with that engine because it was the best available at the time.

You can easily achieve maximum hull speed with a 28hp engine and a 2.6:1 reduction with a 17" prop, or if you have not got room for 17" use a 2:1 box and a 15" prop. There is a similar boat to yours for sale in the Channel Islands which has been re-engined with a Beta 28. My boat is over 1 ton heavier than yours, but with a slightly longer waterline and is quite happy with a 29hp Volvo.

You will find "pressure" to go up a size, but it is really not necessary. There is a significant saving in price, size and weight with the 28hp engine and arguably better to put the money into a good prop than power you don't need and can't use.

 

[Boo2]

If you are going to all this trouble to fit a new engine, best to specifiy a folding prop, then your problem of whether to lock or spin the prop goes away.

Actually, Sunrunner is currently fitted with a 2-blade folder and the shaft still does spin under the circumstances I mentioned. I think one blade must drop and then the spin results and brings both blade out. As I said, I can get it to remain still provided I stop the engine while it is in gear.

The prop currently fitted is a 17x12, I think there is plenty of room to go an inch bigger (see attached).

I sized the engines by asking the various manufacturers the open question and specifying the boat. I do understand that diesels are likely to last a bit longer if they are run at nearer to maximum output rather than 50% but there are advantages to 4-cylinder engines too which all the 35-38hp engines are. Pros of the smaller engines are they are lighter and cheaper and presumeably more fuel efficient since running nearer their rated output.

Boo2

 

[Kurrawong_Kid]

I don't think you said what your previous engine was. Be aware that the majority of new engines are right handed, whilst old Volvos , in particular were left handed. You may need a new prop. but if you don't then you need a gearbox that can be run in reverse to spin a left handed prop right handed. alk to the engine makers as to which is the best gearbox if this is the case.

 

[Boo2]

I don't think you said what your previous engine was. Be aware that the majority of new engines are right handed, whilst old Volvos , in particular were left handed. You may need a new prop. but if you don't then you need a gearbox that can be run in reverse to spin a left handed prop right handed. alk to the engine makers as to which is the best gearbox if this is the case.

It's a Thornycroft 90 (BMC 1.5). The current prop is right handed (turns clockwise for forward when viewed from astern) but I am more or less resigned to buying a new one anyway - seems pointless to spend on a new engine and bits and not get the most from it due to saving on a new prop.

Thanks for your interest,

Boo2

 

[Tranona]

As I suggested the "pressure" is there to sell you the next size up - you can see plenty of examples of new boats fitted with engines that are too big (or rather bigger than necessary). This happened a lot in the past such as Centaurs with 23 hp because there was a big interval between engines eg 10hp, next size up 20. However, now there is a much wider choice of hp and gear ratios so easier to get a good match.

Nigel Calder in one of his books on engines has a formula for calculating optimum engine size and gearing. Might be worth finding it and doing your own sums. The simple formula I used was the Propcalc one and putting in the different combinations of engines/gearbox ratio/prop. Any combination with 28 or 35 hp easily gets maximum hull speed, but of course prop sizes vary and you really need an 18" for the 35, and a 17 with a 28.

You might want to reconfigure your shaft length as currently you have far too much overhang aft of the P bracket. The shaft anode should fit the other side of the P bracket. Gap aft of the bracket should be about 15mm, but obviously more if you fit a rope cutter.

 

[stearman65]

Hurth Gearbox

Our Hurth Gbox seized when we took the yacht over in Corsica, stupid previous owner didn't inform us it was loseing oil. Had the choice of a new or re-con box, chose the new Hurth, got as far as Toulon where we were changing the engine & found the new box had a "Slow Engagement" problem, sent it to the local Hurth agent who fettled it under warranty, not enamoured with Hurth though.
Stearman65