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Old 26 April 2015, 15:16   #11
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The pilot screws on each carb were only 1 and 3/4
Turns out. Would this make a big difference to the idle speed pull away?

Also last time a took carbs apart there was a small rubber bung over one of the jets, but can't work out how the fuel gets sucked up. On my motorbike carb the jets need to be open to suck fuel.

Baffling.
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Old 26 April 2015, 16:32   #12
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Quote:
Originally Posted by Commando C2 View Post
Good info thanks. Will see how the carbs look.
I have some spare coils from my other engine that is running sweet so might swap them out. Going to add additional earth strap between coils too.

I did pull the plug lead off number 1, then start it and it felt the lead had a spark, then did same with other 2 so if one was down and one taken off it surely wouldn't start on one cylinder.?!

I think its not coil related as I was getting 40 mph out of it once it got planing....a duff coil normally shows up at top revs.
if you can try taking the spark plug boots off while it's running, makes it easier to tell if it's firing on that cylinder, just be careful of shocks

My tohatsu amazingly would run on 1 cylinder, not too happily of course...

When I had that coil issue, it was intermittent, sometimes at WOT the dodgy coil would suddenly come to life. With the aftermarket coils I've got now the only issue I had was a corroded earth, just needed cleaning up with sandpaper and then some vaseline.

Saying that the other weak link on a tohatsu 50 is the fuel pump, again I've replaced mine with an aftermarket part from a jetski. Original required 5 rebuilds in one summer, poor quality part and that's with 2 fuel filters
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Old 26 April 2015, 16:34   #13
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on a probably unrelated note, 40mph seems a bit slow? What propeller have you got on it?
With a stainless 15p bunny you should be getting around 46/47 with a zapcat, maybe 48 with a thundercat. Or get an 18p prop and you'll be closer to 60mph
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Old 26 April 2015, 17:06   #14
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Its a 15p prop semi cleavr type for Zapcats.
I thought 40 was pretty good. I was against a tidal flow of about 6 knots at least and had about 35 kgs fuel in front of boat and a 10ft surfboard strapped across the bow .
I like the sound of an 18 pitch prop though.

Will check all the carb and fuel pump and other recommendations this week.
What make coils do you use now rolfhat?
Thanks all for your help.
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Old 27 April 2015, 04:19   #15
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Ah ok, so you're probably at ~ 40 knots ish top speed, thats decent.
i generally keep all the weight, fuel tank etc. as far back as I can unless I'm in big waves with just myself onboard.

Here's my tohatsu 50 build thread on here - My thundercat
They're nakuru motorbike coils, there's been a couple of discussions about them on here since as well.
Once you start with cleaver props and chasing numbers you can't stop
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Old 27 April 2015, 11:52   #16
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Thanks Rolfhat, will try to the plug cap removal next time I get to tinker.

I keep the fuel at the front to make more room for passengers at back and so front is weighed down a bit as some times boat is driver only and some waves to get back through.

There was no link to your thread in last post
Was there meant to be? Would be interested to read that .
Thanks
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Old 27 April 2015, 16:47   #17
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link works on my computer? try this - My thundercat
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Old 28 April 2015, 17:59   #18
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Enjoyed looks through your thread..thanks
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Old 29 April 2015, 11:24   #19
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cheers, check out Thundercat Inflatables Forum as well. A massive amount of info on there. I'm Roflhat on there too
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Old 06 May 2015, 05:55   #20
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Have set pilot screws to 2.5 turns out.

Wot timing is spot on 20 btdc
Idle timing was about 5 degrees btdc and offer to be 3 atdc so adjusted the stop.
Carbs all open at wot.

Just need to water test it in next few weeks.
Installed a tiny tach to help with max rpm and idle speed.
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