Fitting 60HP Yami on 4.1m

[Splash]

OK - as you all know, I am having the 60HP Yami (with standard 3-blade prop.) fitted to the 4.1m by the Yami dealer. This motor has a 20.7" leg.

I have read elsewhere that someone else has found that the cavitation plate of a motor with a 20" leg is 25mm below the bottom of the hull - which is far from ideal.

I have also read by another forum member that having the motor 25mm above the transom was too low so it was moved up another set of holes so that it was 50mm above the transom.

Which set of the 4 holes in the transom should this motor be fitted to achieve maximum hole shot speed and to ensure the cav.plate is not below the bottom of the hull?

PS - Yes, I have had the hull re-certified to fit this 60HP motor and no it will not affect my insurance in any way.


Splash

[stevemid]

Splash, I was just down at Brooklyn Marine Yamaha yesterday discussing the installation of the 70hp Yamaha (same dimensions, I think) with their shipwrights. They printed out the Yamaha Outboard Motor Dimensions for me, which I have attached. He said Yamaha's policy is that the selling dealer has to mount the motor for the warranty to take effect and he was quite prepared to drill the holes when they install the motors.

Are you saying that your measurements are different from what Yamaha published? The dimension you're looking for is H4 which for my motor is 21.0" 534mm from the underside of the top of the clamp to the underside of the cavitation plate.

His main point to me was that you can always raise a motor, but you cannot lower it without surgery to the transom. For me (the catamaran I am building, he said, is not technically a planing but a displacement hull) he said to put the top of the transom at a point 21" above, not the bottom of the hull, but a point 1/2" below the bottom of the hull (the inverted peak), then to drill the top holes on the Clamp Bracket Drawing, as well has the two holes at the top of the two 2.2"vertical slots at the bottom of the bracket. Since there are four sets of top holes on the clamp bracket, this will allow me to raise the motor in four 1/2" increments depending on where the cavitation plate rides on my displacement hulls.

Hope this helps.

[finga]

The only way your going to find your ideal motor height is by experimenting.
The best spot to have your motor is so the cav. plate is just skimming the surface of the water whilst your planing.
Distances given by other will only indicate how their boat is setup and unless it's the exact same as your setup (ie battery and fuel tank position, operator position and weight etc etc) the figures are only a starting point for you to work from.

[Noelm]

yeah, what finga said.

[Splash]

thank you people

[Moonlighter]

Hi Splash

Have a read of this article on the Mercury Verado club website. These guys are the gurus on engine heights and props and they expand further on what finga has quite correctly pointed out in his post above. This article is one of the most quoted on the Internet about this topic.

http://www.veradoclub.com/smf/index.php?topic=137.0

Cheers

ML

[Splash]

All,

I read this link from ML, but have a fundamental question in performing these mods - will raising a brand new motor (to avoid burying the plate) void the warranty if damage occurred from overheating?


Splash

[ifishcq1]

the water pickup is well below the anti cav plate, so no you won't overheat the motor

cheers

[finga]

And there's alarms and things to tell you if something is getting hot as well.
Those engines might even go into 'limp mode' if things heat up.
But they won't heat up if you get the motor sitting like in those pictures. The outboards are made to sit like that.
It's just dealers who mount them way too low for what-ever reason.

But be warned. It may take a few goes to get the height right. A hole higher each time is the best thing to do.
The end result will be well worth the time taken to get the height right.

[Splash]

so, will raising the height of the engine compromise a new motor warranty in any form?

Splash

[Mudlicker]

Thats a big NO , mate what you should do is ask for a water test and go with them if you a really worried about the whole thing .I have had 3 yammies now and the dealer has never questioned me raising the motor. I helped him fit the last one and we put it right where the previous motor was fitted and he did not bat an eyelid .

[ericcs]

if the motor is that high out of the water, cavitation will be more of an issue than overheating

[Fallen angel]

Hi Splash

Out of curiosity what make of boat are you putting this on? I did the same thing years ago I put a 60 Bigfoot on a 4.1 fishseeker (very sweet setup). My only advice is to also look at something like a SE sport to assist coming of the plane as you will find that it will come off quickly.

Enjoy your new setup, I used to get upto 45-47 mph out of mine.

Cheers

[Fed]

It's a PorpoiseCraft Fallen angel.

[Splash]

Thanks guys -

4.1m polycraft with a 4 stroke 2012 Yami 60HP.


Splash

[Giffo65]

It's a PorpoiseCraft Fallen angel

I have had my 4.55 Polycraft for 10 years, with a 50 two stroke Yammy and now upgraded to a 60 four stroke Yammy and never a porpoise problem.

[finga]

It's a PorpoiseCraft Fallen angel.
would you like to expand that a bit please?
I don't really understand. Sorry :(

[Fed]

They have a bit of a reputation Finga but having said that Giffo has never had a problem.
4.1M + 60HP sounds like a perfect test, time will tell I guess.

[Giffo65]

Splash's 4.1 will not be a Porpoise but a Wahooooooooo with that power !;D