70 HP Yamaha installation

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Windy C
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Joined: Thu Aug 11, 2016 7:58 pm
Sailboat: MacGregor 26M

70 HP Yamaha installation

Post by Windy C »

We are about to have a 70 hp Yamaha 4 stroke installed on our Macgregor M. Are there any specific recommendations we should be aware of? The work will not be done by a Yamaha dealer or by anyone familiar with the Macgregors, just our local marine shop. Prop recommendations, shims to trim the engine, any recommended mounting issues on the transom? What speeds and fuel consumption are likely to result? All this is of interest to me. Thank you much for your help.
Whaler Sailor
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Joined: Thu Jul 30, 2020 8:22 pm
Sailboat: MacGregor 26X

Re: 70 HP Yamaha installation

Post by Whaler Sailor »

I have a Yamaha 70 but its on an X not a M.
I just changed from a 13x11 3 blade aluminum prop to a 14x9 4 blade stainless, from Turning Point.

The 3 blade proformed as follows.
Note 2 men onboard with 24 gallons of fuel and fully loaded.

2000 rpm 5 mph
2500 rpm 6
3000. 7.4
3500. 8.1
4000. 9.5
4500. 12
5000. 15
5500. 17.
6000. 19

Max RPM 6000

The Turning Point averaged around 1.5 mph faster at each increment.
Max RPM 6300.
Max speed 21.9
I think it spun up to 6300 to easy. There was about 10 percent throttle left when it reached 6300
I am considering taking it to my prop guy to add a little pitch.
Hope this helps.

Edit
Just did the slip calculations
0.04965
Crazy, right?

2nd Edit
When i add 1.5 to pitch as an allowance for the cupping i get a more realistic number.
0.18541

Image

Image
Windy C
Posts: 3
Joined: Thu Aug 11, 2016 7:58 pm
Sailboat: MacGregor 26M

Re: 70 HP Yamaha installation

Post by Windy C »

I was planning a likely 14 by 11 prop. What do you hope the advantages of your prop will be over this one? Did you have to add any type of shims or the like on mounting the engine to get the bow down?
Thank you
Windy C
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1st Sail
Captain
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Sailboat: MacGregor 26M
Location: Moline, IL '06M 50hp Etec
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Re: 70 HP Yamaha installation

Post by 1st Sail »

My Etec 50 WOT 6000 rpm, 14 x11 prop, 2 adults, 2 anchors, 2 batteries, cooler, lightly loaded for the day, 18gal fuel, 18mph+. 13x13.75 same on board, 17+, 5,600rpm. Tested on flat water, no wind, no current. I never run the 13 x 12.75 WOT so as to not overload the engine. I would think the 14 x 11 @ 6300 would be about right as you add more weight on board.
:macm:
Whaler Sailor
Posts: 6
Joined: Thu Jul 30, 2020 8:22 pm
Sailboat: MacGregor 26X

Re: 70 HP Yamaha installation

Post by Whaler Sailor »

Windy C wrote: Sun Aug 02, 2020 10:19 am I was planning a likely 14 by 11 prop. What do you hope the advantages of your prop will be over this one? Did you have to add any type of shims or the like on mounting the engine to get the bow down?
Thank you
Windy C
I have had the 70 Yamaha 3 years with the aluminum 3 blade 13x11 that was originally installed. Max rpm 6000 empty and no ballast.

I ran it this morning with ballast full and only hit 6100rpm with the new 14x9 4 blade stainless Turning Point prop.
I am going to take to my prop guy and have him add pitch to make it a 14x10 or cup what ever he suggest after i share data.

I hope to achieve lower rpm while on plan.
Less strain on motor becuse unlike the 13x11 aluminum (max rpm 6000)
The 14x9 is a 4 blade and easly hits 6200 with no ballast right now. With 10 percent of throttle unused.

The motor was shimmed when first installed.

I was seriously considering Etec but the 260 pounds of the Yamaha was the deciding factor for me.
I am glad i went that route, because i don't thing Yamaha will go out of business any time soon.

All things considered, I dont think my motor can spin a 14x11 Aluminum or Stainless 3 or 4 blade prop to 6200 rpm.
If it can't spin a 13x11 3 blade aluminum to 6200 how could it spin a 14x11 to 6200?
Note " My option only"

Whereever you end up make sure you motor reaches max RPM.
Our hull are not exactly sleek or easily planned.
Haveing the motor dailed in is important to longevity.

Cheers
Windy C
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Joined: Thu Aug 11, 2016 7:58 pm
Sailboat: MacGregor 26M

Re: 70 HP Yamaha installation

Post by Windy C »

What degree of angle are most people shimming these engines to for their Ms?
Whaler Sailor
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Joined: Thu Jul 30, 2020 8:22 pm
Sailboat: MacGregor 26X

Re: 70 HP Yamaha installation

Post by Whaler Sailor »

I don't know what others are doing.
I did 5 degrees.
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windypatrick
Engineer
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Re: 70 HP Yamaha installation

Post by windypatrick »

Is there a special variant of the 70hp Yammy you ordered? I was thinking ETEC, but of course now Yamaha sounds good...possibly nexty year before we take the boat south.
Whaler Sailor
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Re: 70 HP Yamaha installation

Post by Whaler Sailor »

Not really.
Plan old F 70
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Tomfoolery
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Re: 70 HP Yamaha installation

Post by Tomfoolery »

windypatrick wrote: Fri Aug 07, 2020 4:07 pm I was thinking ETEC . . .
They’re stopping production of the ETEC, so I would stay away. Which stinks, because they’re great engines, and small for their power output.

viewtopic.php?f=7&t=27706
Tom
Be seeing you . . .
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