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Thread: My Thundercat

  1. #121
    Team Member Roflhat's Avatar
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    Got out for a blast last night, weather was really nice, not warm though!
    Engine is up at 70mm and revving a bit higher but roughly the same speed, 57.5 knots with myself and my girlfriend in it.
    Went into a cave with it -


    At the beach


    hopefully a video attached from Sunday as wellIMG_8503.MOV

  2. #122
    Team Member Roflhat's Avatar
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    Was down at Easdale over the weekend at the Rib Rendezvous, had a really great time. Had an issue with the pull start before the event started, managed to get it fixed just in time on Saturday morning and caught up with the rest of the RIBs, over 30 the first day!
    Covered over 90 nautical miles on the first day, plenty of chop so gave the boat a good run. Also some nice calm sections to go flat out, used around 80 lt of fuel - thirsty!






    The thundercat was a very wet ride but a lot of fun!
    Thanks Ron Hill thanked for this post
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  3. #123
    Team Member Roflhat's Avatar
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    Boat and engine have been going really well lately, spent a lot of time cruising around here. Spent today fitting the primer kit in place of the chokes, haven't tried it yet but hopefully it should work well.


    Should allow improved airflow as well, gives the air a clean channel down the carb throats


    I also designed a new roller for the pull start, the old one was a bit worn!
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  4. #124
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    Roflhat,
    I'v enjoyed reading your post. Nice looking rig you have there.

    I am building a Tohatsu M40D2 like the one you had. I have some Yamaha 60 carbs to go on it with the chokes removed. I will need to install a primer system like you did here. Is the primer electric or manual? Could you post a picture of the actual primer?

  5. #125
    Team Member Roflhat's Avatar
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    Thanks very much, glad you're enjoying it!

    Sounds like a good build, I'm following your progress on here. It's all manual, I have no electronics on this engine.
    I put the primer where the key start would normally go in the tiller, just took some filing and looks pretty good I think

  6. #126
    Team Member Roflhat's Avatar
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    So unfortunately looks like my photos can't be seen any more, photobucket wants $399 a year to host them... If I have time at some point I'll try upload them to a new site and edit all the posts

    Recently changed the head on the Yamaha, removed the TSR one and found it was letting in water


    so I've stuck the original head back on, performance seems about the same but waiting on some flat weather to get top speed figures. The old head isn't in great condition, if anyone has a spare 70ces head kicking about please give me a shout!


    Also found that there was some flex in the transom, more than I'd like so I had another jack plate waterjet cut, 12.7mm thick so I could countersink bolts and have the plate flat against the transom which should reduce the flex. Also had some pull handles cut using the spare ali, these ones are a wee bit too big to fit through the cowling unfortunately so I'm having another made.


    Tried the original 70hp carbs on, the engine just won't run properly with them, feels like it's running on 2 cylinders. I've rebuilt the carbs with new gaskets, cleaned the jets with carb cleaner and the airline and the jets are immaculate, so not sure what it could be. Also very hard to start with them, put the 90hp carbs back on and it starts easier and runs fine

  7. #127
    Team Member Roflhat's Avatar
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    Had some excellent weather last week, got out for a spin and got some footage with the drone

  8. #128
    Team Member Roflhat's Avatar
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    Not got out in the boat so much lately, getting into winter now.
    Had the original cylinder head reconditioned, looks really good. Interestingly the genuine Yamaha head gasket is around 1.4mm, the aftermarket one is 1.2mm so might increase the compression slightly.

    Trying to get the engine to work with the standard carbs too, it just isn't happy with them, won't idle and it feels like it's dropping onto 2 cylinders. I've now had them put in an ultrasonic bath so I'll try them again. Designed another version of the throttle roller as it still wasn't getting WOT with the standard carbs. Unfortunately the roller broke when I twisted the throttle, so having another made in a harder material.

    Looking at having the flywheel lightened too, not by much. The homologation sheet for the 70ces says 3800 grams so I'll take it to that, it will obviously be heavier due to the pull start attachment on the top. I'll have it balanced too, I suspect it's fairly well balanced from factory but won't hurt to have a finer tolerance




  9. #129
    Team Member Roflhat's Avatar
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    Got the engine running yesterday and out for a run. Starts a lot easier now and runs smooth with the standard carbs and head which it hasn't done before. Throttle isn't opening fully yet - waiting for the new throttle roller to arrive.
    New trailer arrived last night


    Photo of some of my props


    Did around 26nm yesterday, was nice weather but the throttle grip is still far too slippery so I removed the rubber section and designed a new one

    hoping to have it 3D printed in ninjaflex which is pretty rubbery and flexible
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  10. #130
    Team Member Roflhat's Avatar
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    3D print turned out really well, the grip feels really good. Very flexible too, just like the original rubber part but far grippier.



    Got another throttle roller, made of resin so should be a lot stronger. The surface finish is completely smooth too, very nice piece


    Bought this prop, was last used on an offshore racer with a Yamaha 60DES in the 80's. Looks sort of like a Hoss cut chopper, says 11x20 on it but measures closer to 10.5" diameter. Should go well on the Yamaha, possibly even better on the Tohatsu which seems to prefer overhub props
    Likes camohunter liked this post

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