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Thread: Trialing new F70 Yamahas on my 5.2m Kevlacat

  1. #121

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    Pretty sure this is the Merc prop in question (please correct me if I am wrong) ... http://www.boatpropellerwarehouse.co...r-48-854354a46

    Looks like this is the hub you need for Yamaha 60's ...
    • Yamaha 50-100 HP - use hub kit 835272Q1


    Definitly validate all of the above with your friendly Merc dealer.
    Sunshine Coast - Kevlacat 5.2

  2. #122

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    update rung another dealer just to shop around as you do and they wanted $775 for the vengeance prop

  3. #123

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    You Guys have got me thinking now , very impressive numbers for Mercury 60 , would like to see how they go with the yami high thrust 60's , could be the solution to some of the 5,2 owners including myself , would love to hear how they go with the yami,

  4. #124

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    I'm very keen to try them but finding a set to trial is nearly impossible. and bit of a risk just buying them. although both motors have same gearbox ratio and also same displacement cc wise and the bore and stroke are the same from what i can gather so hoping these props will work the same on the yammie
    Quote Originally Posted by fromeo View Post
    You Guys have got me thinking now , very impressive numbers for Mercury 60 , would like to see how they go with the yami high thrust 60's , could be the solution to some of the 5,2 owners including myself , would love to hear how they go with the yami,

  5. #125

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    I am heading out on the weekend and have fixed a couple of trim issues so will get another good chance at seeing the performance of the shaved Yam props. I am feeling that a slight but more could come off them.

    Sunday I was sitting on 5600rpm coming home topping out at 54kph but I wasn't able to get full trim out of the motors. I think I have fixed that issue now so will report back on Sunday.
    Democracy: Simply a system that allows the 51% to steal from the other 49%.

  6. #126

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    If and when I re power my Kevlacat, should the fuel tanks be checked. As you know, it means cutting out the floor etc. The boat is a 94 model. Any history to suggest I should inspect these fuel tanks?

  7. #127

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    Can't comment on the fuel tanks Dan,

    Just to report back on the latest trip to the northern banks and the hards on Sunday. Still having some minor trim issues where the guages think that I am at max trim and wont allow me to trim the engines all the way until they ventilate whilst underway. If I stop and bring the engines back to neutral revs I can trim them to where I want but taking off like that is a pain. In glassed out conditions with 100l less fuel but about 80kg of fish plus a fair bit of salt water (50L?) in the slurry and 3 POB I was topping out at 55kph @ 5700 RPM WOT.

    Debating wether I should have a tiny bit more shaved off the props to achieve 5800-5900RPM WOT or wether the props as they are won't lose too much longevity only achieving 5700RPM?
    Democracy: Simply a system that allows the 51% to steal from the other 49%.

  8. #128

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    Lovey80 .. my personal opinion after having run the 15K props , on my 5.2 I was getting at WOT about 5600 in heavy loading and 5800 in light trim , I recon you need a bit more off to give you another 200 RPM .. I now run 13Pitch alloy Solas which have much better grip and good for the heavy loads I carry ( 4 guys ,full tanks , lots ice etc) . but the downside is that you will cruise at 5000rpm but effortlessly and the motors do not struggle, That;s my experience with the Yami 15 K's on 60HP high Thrust... good results of the Mercury Vengeance props though they would seem to be the go if you could get a hold of a set to trial ...

  9. #129

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    What were the WOT figures on the Solas props?
    Democracy: Simply a system that allows the 51% to steal from the other 49%.

  10. #130

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    WOT fully loaded with 13P alloy amita props 5900 RPM ... would easily hit the rev limiter in light trim ...forget the 15P in solas to much prop , the 14P may be what would suit you...

  11. #131

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    Quote Originally Posted by fromeo View Post
    WOT fully loaded with 13P alloy amita props 5900 RPM ... would easily hit the rev limiter in light trim ...forget the 15P in solas to much prop , the 14P may be what would suit you...
    what was the top speed at 5900?
    Democracy: Simply a system that allows the 51% to steal from the other 49%.

  12. #132

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    Top speed 28 knots absolute top ,flat water I don't believe you will get much more with the 13p ... but hole shot is great , don;t know if it would do any better with the stainless.

  13. #133

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    I couldn't wait any longer to discuss prop choice (had spun a prop .. and they were pretty beat up anyway) so I pulled the trigger on a set of standard props.

    I will however get them cupped as Gav McMullin on the Sunny Coast reckons thats a good choice for standard props.

    Question is ... who does that in Brisbane and what do I ask for ? I believe there is one one guy in the area that does this type of work ?

    Cheers

    Steve
    Sunshine Coast - Kevlacat 5.2

  14. #134

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    If anyone is chasing a set of the 15p merc vengance props shoot me a pm ... $500 each

  15. #135

    Re: Trialing new F70 Yamahas on my 5.2m Kevlacat

    Quote Originally Posted by Danf View Post
    Thanks for the response guys. I have owned this boat since 1995 previously owning a 565 Haines since 1981. The KC has been sitting idle in the shed for a long time. It is now come to a point that it needs new motors, if I intend to use it again. Re powering with the RIGHT motors is under consideration. The issue is, do I stick with 70 Yamaha 4 strokes at 120 kg, or go with a set of 90,s which all motor brands are heavier due to their larger engine displacement. The weight difference being up to about 40 kg each. These larger motors will need extra buoyancy in the pods, a new set will have to be made. I have spoken to a long acquaintance of mine who has been making alloy cats for a long time and he has reckons to make a set of pods which are an extension of the hull, as opposed to the existing ones which are raised. I suppose we have to work out the extra buoyancy that will be gained with these new pods and how much further back the motors will sit. The boat will still probably not get on the plane with a single 90 hp engine, it doesn't with a 70.

    Speed was never a real problem with the 70 2 strokes although at times during those calm periods the boat seemed to take forever to get there. One thing that I can say is that most trips to the reef, the speed going out was the same as coming home. I would pass a lot of similar sized mono hulls back to port on those not so calm days.
    Just a follow up on this post, I did not realise it was that long ago. I finally got new pair of F70 Yamahas fitted at the end of last year. I have done 21 hours on them and at this stage I can not complain. They are fitted with 15 inch yamaha aluminium props and the height is set the same as the previous 2 strokes.
    The old 2 stokes were fitted with aluminium 17 inch props.
    I have no intention of changing props as I am happy with the performance.
    With 2 people on board and half fuel it revs to 6300 rpm at 63 km/hr.

    Dash 2.jpgDash.jpg

    I am happy with the fuel economy with each motor doing around 3.1 - 3.2 km/lt @ cruise.

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