I'm thinking it might be very useful to have a database of Twister engines props and performance characteristics, on the basis that while you can do all the fancy calculations you want, you can't beat real world experience. I know there is already a listing of all known Twisters, with a mostly complete column for engine, but the engine fitted is only one part of the story. What prop has been fitted to that engine, and then in turn how does that affect performance? Initially - if people agree such a database is worthwhile - then I think it can be free form, ie just a short text description of the installation and its performance characteristics. I'll start the ball rolling with Offcutt's previous engine (I am currently in the process of swapping to a Beta 20 and and am ruminating on what gear box ratio and prop dimensions to install):
Offcutt (late 1990s to 2024): Yanmar 2GM20F, Kanzaki KM2P 2.21:1 ratio gearbox, fixed 3 blade 14 x 7.5 prop: ahead performance: no complaints; astern performance: atrocious - very little or no control most of the time, minimal or no useful prop walk, certainly not enough to counteract only moderate awkward breezes. Stopping power from ahead rather feeble. Other comments: prop aperture larger than on some Twisters, so I can fit a 14 inch prop, but is that at a cost of rudder area where it matters?
Hi,
We are the proud custodians of Sycorax 1979 GRP Twister
We have a Beta 14 engine with a shallow sump, a TMC40 2:1 reduction gearbox, a standard stern gland and a fixed 3 blade Goldline prop 12x8 RH on a 1" s/s shaft. There is a 10 gallon fuel tank. I believe she has a standard aperture.
This engine came with Sycorax when we bought her fitted in situ but not plumbed or wired and has never been run. Hence, as to how she behaves under engine I have no information. I also have no information as to what engine was originally fitted.
Kind regards
Mark and Anne
Yacht Sycorax
Mark and Anne - thanks for your engine details. It will be interesting to hear hear how your engine performs once it is in commission.
One thing I would mention - if your Beta has been standing unused since leaving the factory, it might be prone to run (race) away when first started. Basically a little bit of corrosion can be enough to mean the governor ('throttle') jams fully open and away she goes! Beta recommend inhibiting the engine if it is stored for more than 6 months before commissioning. You might want to check with them what you can do to guard against run away, also have a rag ready to put over the air intake when you do start it just in case. The rag is the only way to stop it, the stop control doesn't work as the rack is jammed!
Hi Chris,
Thanks for that. I'll definitely be sitting with a rag in hand when I start her up.
I spoke to Beta not long after buying Sycorax. They told me to do nothing until I commissioned the engine. As long as the engine was in a dry place she would be fine. She is in a dry place. The bilge is full of dust and bone dry. She came with an old chunky jumper on top of her which is still keeping her walm. The Beta chap told me about one of their engines which has sat for over 20 years before being commissioned and told me not to worry about it.
Kind regards
Mark
Yacht Sycorax
Mark - interesting! I should also not have assumed you hadn't spoken to Beta. Beta's installation manual has this: "If storage is to be more than six months then the engine must be inhibited (contact your dealer or Beta Marine). Failure to inhibit the engine may result in the formation of rust in the injection system and the engine bores, this could invalidate the warranty" (note the 'must') and a Beta dealer told me run away was a real thing, but maybe both are a bit alarmist, it seems the key thing is keeping them dry and so corrosion free, and that keeps the problem at bay. But I would still have that rag to hand, just in case, on first start up!
Hi Chris,
I have just got the manual out and you are correct about what it says. Though when I contacted Beta Marine I was told what I said in the previous post. I guess I'll find out next year if it was correct.
Though now when I run her up. I'll definitely have a large rag to hand.
Kind regards
Mark
Yacht Sycorax
Manuals and other sources of advice and even manual to manual from the same manufacturer recommendations being at odds is common, and it gets even worse if you venture into the wild west of advice (facebook). Yanmar manuals can be particularly bad. This is one of my favourites, taken from a GM series manual: 
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