Zodiac MKIII Prop

[Palssonater]

Took the MKIII out for a rip on the weekend and put my 35HP Evinrude on it. The prop on there is 10x13 for my tin Edson boat. This prop easily got us on plane but topped out at 24mph. I have a 10x15 for a spare that I took off the motor originally, and was wondering if I were to throw that on, what kind of topspeed I would be looking at.

I am thinking this boat, with this motor should be flying a helluva a lot faster!

What do you all think?

 

[steelespike]

Re: Zodiac MKIII Prop

What year Evinrude?I don't know the MKIII while light the hull shape may not lend itself to speed.
You shouldn't play with props without a tach if you end up outside recommended rpm could lead to premature engine failure.
motor height a trim are important too.A test run won't hurt and may give you an idea where your at.
That said a 13 might be light; give the 15 a try if it still seems strong out of the hole and improves speed then you may be better off.Just keep in mind it could lower rpm by about 400.

 

[Palssonater]

Re: Zodiac MKIII Prop

1984 E35RCRR. 20" shaft. The MKIII is a Futura with speed tubes. I would think it would be well suited for speed as it sticks to the water like a train on rails. (first real run with it yesterday and totally impressed). Originally I had the 15pitch prop on the 35 with my 14ft Edson. It was far to heavy for a bit of cargo and people. With 13pitch the boat planed much easier.

It would be harder to turn the 15 would it not, so I wouldn't be over revving or doing damage would I? Or pushing the lighter zodiac put me in the danger zone?

 

[steelespike]

Re: Zodiac MKIII Prop

Is it a 20" transom?The speed tubes may not necessarily mean speed but stable performance at speed.Sticking to the water doesn't sound like
the way to the best speed.But again I no nothing about the Zodiacs.
No the 15 isn't likely to over rev but it may not be able to reach the recommended rpm range over rev can cause it to come apart lugging can cause poor performance,coking,carbon buildup leading to further problems.
The 13 is almost surely not enough for the Zodiac and the 15 is probably close to right.If we knew the rpm with the 13 we could figure the right prop easily and confirm with the tach.The 35s rpm range is 5,200 to 5,800.
It is recommended with todays gas to operate near the top of the rpm range.It also usually follows with the best speed.
if you end up around 5,200 it isn't likely to self distruct but you may get premature carbon build up etc.

 

[Palssonater]

Re: Zodiac MKIII Prop

Not a 20" transom but have it built up so the AV plate is 2" below. I know that the drag created will have an effect on my top end. Speed tubes are for control mostly. However as stated through zodiac it acutally lifts the boat slightly and rides easier through rough water etc. So that should in turn contribute...

Overall I was really impressed with the 13 pitch prop. It planed easily at 1/4 throttle. I will most likely leave the 13 on because the boats main use is not for joyriding, its for hauling equipment and moose hunting. I'll want the torque when I get down to towing a couple thousand pounds across big water.

I think I will try the 15pitch just for fun on a test run.

I do not have a tach although my timing is almost spot on at WOT. I was reading once upon a time that you you could get a tach for twin 2 cycles, but that they aren't very accurate.