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Old 25 March 2021, 04:18   #1
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Anyone own a Gemini GRX 420

Just wondering if anyone on here owns a Gemini GRX 420?

I picked a used one up a month or so back. Be interested to speak to any owners, as I know they are a bit niche.
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Old 25 March 2021, 07:50   #2
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Old 25 March 2021, 08:23   #3
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Would love to hear your thoughts was seriously tempted wit the idea of the GRX or Surfcat for beach launched fun. As you say not many around
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Old 25 March 2021, 09:00   #4
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Click image for larger version

Name:	IMG_7082.jpg
Views:	124
Size:	66.3 KB
ID:	136690

I have a Surfcat
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Old 25 March 2021, 12:03   #5
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Quote:
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Would love to hear your thoughts was seriously tempted wit the idea of the GRX or Surfcat for beach launched fun. As you say not many around
Thanks, i will let you know once i get a chance to use it. Its currently stored in Lincolnshire, and I'm based in Surrey which is annoying. I will hopefully bring it back soon. Needs a bit of tidying up as well. Will give the engine a good service, and replace a few bits.

I've previously owned a Ceasar Thundercar. I'm hoping its going to be 90% a Thundercat, but the practicality of a normal SIB. Certainly the inside deck space seems much larger.

I was put off by a normal SIB due to their sea capabilities. The Thundercats were amazing even in terrible weather, I never felt worried even in big surf or large swell.

Its got the good old Tohatsu 50hp 2S, so should go alright.
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Old 25 March 2021, 12:05   #6
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Attachment 136690

I have a Surfcat
Looks

Who makes that? Is it a Ceasar? What's your thoughts on them?
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Old 25 March 2021, 17:13   #7
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Surfcat is pretty close to the ideal all rounder in my opinion. Almost as fun and fast as a thundercat but with 5x the versatility. When I retire from thundercats Iíll get a surfcat again.
Yeh Ceasar make the surfcat
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Old 25 March 2021, 18:25   #8
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Well Bob hopefully see you on the water - I do think if rib is not the answer then zapcat / surfcat / GRX is a very interesting choice

I would have gone for one but ended up with a Ribcraft 6.8m funny how things change !
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Old 26 March 2021, 05:15   #9
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Quote:
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I have a Surfcat



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Old 26 March 2021, 15:44   #10
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Cool vid ! Are surfcat/grx420 less slammy that the typical sib (compared to ribs)
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Old 28 March 2021, 05:18   #11
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They almost never slam, very occasionally have a hard landing when you jump a wake and land on the following peak. But in normal use they never slam, got a cushion of air between the hulls which dampens the ride
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Old 30 March 2021, 15:35   #12
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Thanks for all the information. Certainly looking forward to getting out in it.

Not sure if my arm will last long hanging onto a 50hp. My old Thundercat had a steering damper. This hasnít, so it will be interesting to see how much I have to fight if it.
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Old 31 March 2021, 02:52   #13
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There's a tiller extension + damper set up for sale on ebay just now
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Old 31 March 2021, 04:02   #14
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Yes, I did see that. That's the exact same setup i had on my Thundercat. Have you ever driven one without a damper?

I'm keen to try it without first to see what its like. The previous owner said he kept it standard so there was more deck space inside the boat.
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Old 15 May 2021, 16:16   #15
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Managed to get my trailer engine support made and fitted. Itís slightly to low at the moment, so need to adjust the cross member itís bolted to, but should work as intended.

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Old 17 May 2021, 16:00   #16
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Managed to do a bit of work on the engine tonight.

Started off with the impeller. I dropped the leg off and opened up the housing. Impeller was ok, but I noticed that the housing was cracked, so Iím going to need to order a new one. So I put all the old bits back in.

Iím not sure if this is common, but I had a cracked housing on my Thundercat Tohatsu 50.











I did manage to empty the gearbox oil out and it looked clean which is positive.

Any marine grease recommendations?
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Old 20 June 2021, 09:41   #17
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Finally got the boat out for its first outing.

Engine wasnít 100%, so Iíve currently got the carbs off for a clean and ordered some new coil packs. I will also get a few new bits, like fuel pump kit etc. Hopefully this should sort it out.

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Old 09 July 2021, 15:50   #18
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Well had the boat out this week. Launched down at Loe Beach, in Cornwall.

Iíve recently replaced all the coil packs with upgraded Naraku racing ones, cleaned all the carbs and rebuilt the fuel pump. The engine is running much better now.

Thanks Roflhat for all the help and advice!

Top speed was a bit slower than I had hoped. However Iíve noticed the throttle isnít opening fully, so I need to adjust that. I might also take off the prop guard to see how much that takes off the top speed!
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Old 15 July 2021, 14:37   #19
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Throttle now adjusted - hopefully correctly.

Flaps are now fully horizontal at WOT on the tiller.

Heading down to Hayling Island tomorrow to launch at the Ferry Boat.

I think I might also unbolt the prop guard as well and see what difference it makes.

Not sure where we will head yet, probably just head out of the harbour and see where takes our fancy.
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Old 16 July 2021, 02:06   #20
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Take that prop guard off, will never go back on
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