SELVA outboards info wanted

[puddleduck]

Just become the proud (probably deluded) owner of a Selva 495 XSR racing motor. Does anyone out there have any workshop manuals or parts books for Selva? I think the S495XS, S525 25/35 HP models are all the same basic motor.

When you've stopped laughing please have a rummage in your archives!

[se7en]

"SELVA" ....!!!! ........... ........................Sorry Puddleduck, couldn't resist, .............and it was little Se7en that brought it to your attention...!!...

[puddleduck]

For those who are desperate to hear more, I'm making some progress: a date stamp on the starter motor (april '91) supports the view it is an early/mid 90's motor. We emailed the factory for information today (in Italian!) in the hope it may generate response, and I've also ordered a parts manual CD online for the grand sum of £4.49! Other research has given me the name of the guy who was the UK Selva dealer in the 90's, so hopefully will have something to work with in the next week or so.

Chatted to German circuit racing people at Dusseldorf boat show last week, and this particular size of motor was used in the T550 class, which is no longer raced. The boats were a smaller version of the T850 classs we have over here.

did a compression check today, seemed to be very high (190 psi top cylinder and 170 on bottom cylinder) however not sure if my ancient compression tester is accurate any more, but at least the pots are within 10% of each other, which is good news.

will keep you all informed!

[se7en]

That date stamp........not the 1ST April by chance..??.......

[puddleduck]

Harsh, very harsh! Clive, what do you reckon on the compression - is that unusually high or about right for a racing motor?

[se7en]

190 seems a little high for a 2 stroke, but 170 although still a little high, is closer to what I would have thought, still, give it a try, most performance 2 strokes of this type, I would expect to see around 120-140, dependent on how high or 'wild' the exhaust port is, higher the port, the lower the compression, but within reason , the higher the exhaust port the faster the transfer, and the higher the rev range , there is much more to it than that, but thats the basics..............Oh.......and you will also need some sparks....!!

[puddleduck]

Well, Rapier and I actually got the Selva fired up on Saturday! Revs ran away a bit so the carbs need cleaning out, however plonked it on the back of Thunderbolt III, looks the part! Managed to rig the fly-off throttle ok, worked out the wiring, there's no charging circuit so will just run off a battery. Will hopefully get it running well enough for Ivy lake. Gave Thunderbolt's bottom a birthday, one coat clear epoxy then two coats of ZingaCeram MIO - a micaceous iron oxide ceramic filled epoxy! Nice battleship grey colour, should be easy to spot when upside down!

[puddleduck]

Bit disappointing at Ivy lake. made loads of noise and smoke and ran a treat in neutral but wouldn't start in gear, so couldn't go anywhere. Several theories put forward:
- prop too big - 3 blade 10 3/4" x 17 1/2" surface piercing job. Anyone got anything smaller, it's a 14 spline, so obviously none of my 11 or 13 spline merc props fit. is this Yamaha?
- too deep in the water for a surface piercing prop
- direct gear ratio? checked that, it's about 2:1
- electronic ignition failing under load - a possibility

any ideas gratefully received! Oh, and another thing - there's still a bloody leak in Thunderbolt III somewhere!

[Charles]

Excuse my ignorance, what type of hull is Thunderbird 3? as that's a 50 mph prop on the right hull.

1 carb or 2?

489cc, 72x60.

Is the gear ratio 27 : 13, 2.07 : 1?

Did you say that was a fixed gear box? As that looks like a shift lever, electric start on a race motor is very unusual.

A picture under the cover might explain a lot.

[Charles]

Missread the boat name, when I searched on Thunderbolt III, I found pictrues, oops.