My thundercat - Page 19

Roflhat · 21 December 2018, 17:12

Put the new steering damper on today, old unit weighed 3.44kg all in, new one is exactly 0.5kg. Pretty decent saving and on the maximum stiffness it feels on par with the old one.

Roflhat · 10 January 2019, 13:12

A couple more wee things done, got the lower cowl and gearbox painted.
I sanded the skeg down some more along with a couple other tweaks.

Also designed a new cap for the end of the tiller, the trim switch always annoyed me. Probably saved around 20 grams too!

D-tox · 21 January 2019, 09:58

Nice work you are doing here! been following for a while as a guest.

What work is involved to convert a long shaft 70 to a short shaft? , cant find any info on the net

I can see yours was a modified long shaft, so its do-able ..

D

Roflhat · 21 January 2019, 10:20

Thanks very much.

Mine has only had the mid section cut, the gearbox, transom bracket etc. is all genuine CES. The mid was already cut when I got it, it's a neat job, looks like you can just cut and weld the sections together with 5" removed. If you were starting with a normal long 70hp you would want to change the gearbox to a smaller 13 spline box, either the 1.86 from a 55 or the 1.71 from the racing 70c or 60d

D-tox · 21 January 2019, 11:59

Quote:

Originally Posted by Roflhat

Thanks very much.

Mine has only had the mid section cut, the gearbox, transom bracket etc. is all genuine CES. The mid was already cut when I got it, it's a neat job, looks like you can just cut and weld the sections together with 5" removed. If you were starting with a normal long 70hp you would want to change the gearbox to a smaller 13 spline box, either the 1.86 from a 55 or the 1.71 from the racing 70c or 60d

okay, looks like I can get a original 70ces, it has a 1 piece head (thought they all were) trying to get more info on prop, tiller, pull start etc ..

D-tox · 21 January 2019, 12:27

sounds like it is a 96 model,
one piece head
elec start (no pull)
no prop
dead standard with 165 psi cylinders ..

Roflhat · 21 January 2019, 12:41

Sounds like a good engine, the 1 piece head is quite a bit faster. None of the 70CES came with pull start, you can convert using parts from the 60 Yamaha enduro, need the bracket, pull start pieces for flywheel etc and the cowl.
You can use almost any tiller, the newer style like I’ve got you need to flip the gear inside the tiller to convert from push to pull. There’s a kit you can buy now for £25 odd I think.
Only props that came standard on the ces are the 19G and 21G cleavers, both very sought after props nowadays

Roflhat · 14 February 2019, 21:37

Been doing bits and pieces to the boat, tried some flexi paint on the fuel tank which seems to be working alright. Not sure how long it will last though

Got an update today on the new boat, looking good, very pleased with the black valves instead of grey

Engine is nearly ready too, I'm away march until june so doubt I'll get a chance to test it, will be exciting times when I get back

Roflhat · 25 March 2019, 21:21

Boat is now finished, should be arriving in the UK this week

Hogmonay · 26 March 2019, 01:16

Quote:

Originally Posted by Roflhat

Been doing bits and pieces to the boat, tried some flexi paint on the fuel tank which seems to be working alright. Not sure how long it will last though

Got an update today on the new boat, looking good, very pleased with the black valves instead of grey

Engine is nearly ready too, I'm away march until june so doubt I'll get a chance to test it, will be exciting times when I get back

Assume if you’re away, we won’t see you at Easdale?

Roflhat · 26 March 2019, 07:17

Quote:

Originally Posted by Hogmonay

Assume if you’re away, we won’t see you at Easdale?

Sadly not, I intended to be but I'm working in Norway for 3 months, skippering this

69cmw · 26 March 2019, 09:20

Quote:

Originally Posted by Roflhat

Sadly not, I intended to be but I'm working in Norway for 3 months, skippering this

Seamus, get it delivered to Norway [emoji41]

Hogmonay · 26 March 2019, 14:10

Quote:

Originally Posted by Roflhat

Sadly not, I intended to be but I'm working in Norway for 3 months, skippering this

Shame, as the Norway job looks depressingly mundane! Do you need any crew?

Roflhat · 15 April 2019, 18:16

New boat has arrived, fortunately the engine isn't done yet or else I'd be itching to get testing. Bought an old motorbike windscreen on ebay today, £13, the idea is to mount it on the tiller in front of the cowling to improve aerodynamics.

Roflhat · 27 June 2019, 20:11

Will be working away until the end of next month in France, still waiting on the powerhead so testing will have to wait

Roflhat · 31 July 2019, 09:23

Back to it at last, got the engine put back together on Friday and started testing. Had a few teething issues but the power is absolutely unreal. A lot better than it ever has been before, and still lots of testing and setup to do. Was having fuel issues, now onto ignition problems. Was all set for the race in Harris on Saturday when it started running on 2 cylinders, no fire on number 1. Tracked it back to what I believe is a faulty pick up beneath the flywheel.

If anyone has some spare pick ups (those black things beneath the flywheel) for a 60/70 Yam please let me know

Got some fancy new parts to try, and typical now that the weather is good enough to test high speed props I get engine problems.

Some helping hands working on the boat

Roflhat · 15 August 2019, 08:14

Got some testing done, 61.58 knots with the prop I set the record with. Engine wasn't revving enough so tried leaning it out with smaller jets but lost 4 knots. So now put bigger jets in all 3 carbs and will see what happens.

Still got problems with the ignition, tried new plugs and switching coils but no luck. Tested the resistance of the stator plate wires and they're all within spec so I've borrowed a CDI to see if that is the problem.

Roflhat · 12 September 2019, 12:44

Didn't get anywhere near as much testing as I wanted to this summer, mostly engine problems. Got the whole engine apart now, I had a blown head gasket which was letting water into the cylinders. Cylinders are off for honing, the ports on number 1 and 2 are quite rough in the channels so will be cleaned up again. Ordered new pistons and rings, getting quite expensive this!

Managed to find the fuel additive I was after so I can test that, also going to try ATF in the gearbox.

Got some trials done with the new boat, feels really good, can't wait to try it with the engine going properly again. Old boat weighed in at 84.5kg, new one bang on 80.0kg. Engine was 84.0kg, I've since removed the jack plate and bolts so it's down to 82kg.
New boat is a foot shorter than the F10, no handles in front of the nose cone so it's a bit more aerodynamic too.

jwalker · 12 September 2019, 13:42

Those pistons look to have been picking up on the bores. Marginal lubrication and possibly a bit of particle contamination too. Is that rust on the conrods?

Always jet on the rich side on a 2 stroke. Week mixtures equal excess heat.

jeffstevens763@g · 12 September 2019, 13:48

Quote:

Originally Posted by jwalker

Those pistons look to have been picking up on the bores. Marginal lubrication and possibly a bit of particle contamination too. Is that rust on the conrods?

sea water's abrasive blown head gasket