Trialing new F70 Yamahas on my 5.2m Kevlacat

[Dean1]

Ive spoken to Gav who currently has these 70's on his 5.2kc. He has achieved around 31kts WOT with a 15k prop (15 pitch) as compared to 28kts with the 60's.

He states that the cruise speed/revs 4800rpm =23kts are the same as the f 60's but holds revs better through the swells than the 60's so they do obviously have more torque than the 60's.

So basically to get the extra speed revving the 70's to 6300rpm alows the extra 3 kts of speed compared to the 60's.

He has a set of 16 pitch props ordered from the states so will be interesting to see how they perform. These 16's will bring the revs down say for example 4500rpm = 23kts = more top speed.

The interesting part will be to see if the 70's have the grunt to still rev to 6300 with the 16's as i know the 60's wouldnt have a chance of working they would be terrible with 16's.

The 70's are louder than the f 60's alot more induction noise apparantly.

I havent gone any further into testing them on mine as yet i will let Gav do the hard yards 1st i think.

The motors going onto mine are believed to be Long shaft not XL i have to find out for sure otherwise it would be a waste of time..

Cheers, Deano..

[Greg P]

Not much difference anyway Dean on those numbers?? Unless there was a special price it would be hardly worth considering replacing the F60s. Replacing the 2 banger would be a different story but the price for the 70s would want to be sharp compared to 60s as well.

You reckon Yammie will ditch the F60s for the F70s??

[black runner]

You reckon Yammie will ditch the F60s for the F70s??

Wouldn't think so as the 50/60 is essentially the same motor and apart from the top end, the 70 shares many of the 50/60 components. There are many boats out there with a 60hp max power limit and need this class of motor. Maybe direct injection could squeeze a bit more from the 50/60/70 and I think it won't be too long before the first DI 4 stroke is released by Honda, Suzuki or Yamaha

Cheers

[Chris20984]

He has a set of 16 pitch props ordered from the states so will be interesting to see how they perform. These 16's will bring the revs down say for example 4500rpm = 23kts = more top speed.

The interesting part will be to see if the 70's have the grunt to still rev to 6300 with the 16's as i know the 60's wouldnt have a chance of working they would be terrible with 16's.


The motors going onto mine are believed to be Long shaft not XL i have to find out for sure otherwise it would be a waste of time..

Cheers, Deano..

Any word on how the 16's went. Does anyone have any fuel consumption figures to compare the 60 vs the 70. ??

Cheers Chris.

[Dean1]

No mate ive been meaning to give Gav another call about the props. I think fuel consumption would be very similar 60's 70's. I get 1.3klm per litre and the 90's are about the same.

Cheers..

[Danf]

A good mate of mine works for Yamaha and is currently testing/trialing the new lightweight F70A Yamaha.

Ive been offered a pair of these gems to be trialed on my boat to compare fuel usage, speed comparisons etc to the current F60's on my boat.

This will take place in about a month or so.

Anybody thinking along the lines of repowering their 5.2 feel free for all figures/results from me.

I will be doing an approx 300 klm trip at 1770 with these motors to get a good feel of them.

Hope their not too good or ill be knocking on the bank managers door

Regards Dean.

Dean,
I am interested in finding out more and getting some figures on your Kevlacat upgrade to the F70A Yamahas.

[Danf]

Anyone have any reports on how twin 60 HP Mercury big foot motors perform on this vessel.

[Danf]

Has anyone got any feedback on these F70 Yamis fitted to a Kevlacat 5.2.

[Danf]

Just bumping this thread. Has anyone got any feedback on these F70 Yamis fitted to a Kevlacat 5.2.

[No Excuses]

Hi, I've just put a set of 2010 merc 60 big foots on my 5.2. Running the merc vengeance 14P props. As many blokes will attest to they are the smallest HP that you should run on these hulls but the following is what was achieved. 2 POB, fuel tanks full, some gear and mild conditions. 4800rpm saw 22/23 knots, 5000rpm saw 25/26 knots which was its sweet spot. Fuel burn was 0.7 litres a km combined. Its no rocket but its quiet, comfy and cheap to run.


Cheers Aaron

[Danf]

Thanks mate,
I am thinking about a pair of new motors to replace the 70 yamis 2 strokes.

[Smithy]

I'd be looking at either the F70 V the mid range Suzukis or Hondas. 166kg for the Honda in an XL 90hp and 158kg for a Suzuki 90.

[No Excuses]

If price isn't an issue then the 70/80/90hp Suzuki at 155kg would be the pick. With a 1.5 litre displacement they will be a lot torqier donk than the yammy 70 at 1 litre. Only down side is the added weight. Either build larger pods or put up with it.

[Lovey80]

I think the odd would need to be a significantly bigger pod as 155kg on the bum would be far too much for the 5.2kc to float.

[Noelm]

90Hp makes the old 5.2 a much better boat, but....the weight is the killer, I think there was a thread on here that someone had some bigger pods made? My mate had one ages ago with 90 2 stroke Yamahas on it, and it was so much better than another one I have been in lots of times with 70's.