Twins to single

RIBS! · 19 October 2016, 02:47

I'm thinking of repowering my Zodiac Hurricane 733 from twin 150 hp to a Single Yamaha or Suzuki 300hp. Would I need to get a 300 with a 30" shaft for a single verses a 25" shaft on my twin 150s? It has an 18" transom extension. I have heard conflicting advice on this.

Bigtalljv · 19 October 2016, 03:22

Yes for a single you need a 30" shaft. I assume it's the zodiac bracket? A 250 is plenty unless you really want a 300

Jason

ncp · 19 October 2016, 14:29

And remember, a 4.2L Yamaha 250 is the same as a 300 running 87 octane fuel (in the 300, you need to run 89 or greater octane to get 300 HP). I'd just get the 250!

Fender · 19 October 2016, 15:36

Quote:

Originally Posted by ncp

And remember, a 4.2L Yamaha 250 is the same as a 300 running 87 octane fuel (in the 300, you need to run 89 or greater octane to get 300 HP). I'd just get the 250!

So your recommending a 250hp, but if you then use the same above analogy the 250hp in using 87 octane with be putting out 200/210 hp, RIB might not even pop-up on the plane! lol

ncp · 19 October 2016, 17:17

Quote:

Originally Posted by Fender

So your recommending a 250hp, but if you then use the same above analogy the 250hp in using 87 octane with be putting out 200/210 hp, RIB might not even pop-up on the plane! lol

The 4.2L 250 hp only specs 87 octace. So, no.

RIBS! · 19 October 2016, 22:07

Thanks for all the help.
So I need to look for a 30" shaft.
It is a zodiac extension on the back.
The reason i was leaning towards a 300 is because I feel I need as much HP as possible. Based on the dry weight of the boat being approx 4000 pounds from what I am hearing plus fuel, seating and 12 passengers being another 4000 I think I will need all the help I can get to get this moving at a good speed with out having to push the engine so hard.
However if the 250 technically will do the same thing ill have to look into it.
I'm looking for a good used motor so its allot easier to find a 250 than a 300 i'm finding out.

tworotorturbo · 19 October 2016, 22:42

I know of a local 2014ish Yamaha 300 for 11k, I might get it for my SR7.4 but let me know if you were interested.

What are you going to do with the existing twins?

ncp · 19 October 2016, 22:52

Quote:

Originally Posted by RIBS!

Thanks for all the help.
However if the 250 technically will do the same thing ill have to look into it.
I'm looking for a good used motor so its allot easier to find a 250 than a 300 i'm finding out.

I don't know if my comments help you if you're buying used since you may not find a used 4.2L 250 hp around.

The 3.3L 250hp is a V6 and is not the same at the 4.2L 300 (or 4.2L 250). The 3.3L 250 hp requires 89 octane.

So, let me back up - If I were buying new, and I had to decide between a 4.2L 300 hp and a 4.2L 250 hp, I'd probably choose the 250 hp based on price alone. I'd be ok with a few mph slower off the top end. Torque is what is get you up on a plane, not hp. Both 4.2L blocks will have plenty of torque!

Bigtalljv · 19 October 2016, 23:02

Beat me to it. What are your twins?

My boat topped out at 50mph when it was new no t-top and such. Now it's in the mid 40s.

I could easily pull a wake boarder behind it in Lake Tahoe with 10 passengers on board. Beautiful cruise to emerald bay with 12 on board. Still can't hardly tell the difference between 2 and 12 at altitude.

I cruise 25-30 in the 3400rpm range. 4000 Rpms gets me into the mid 30s I think.

It's not working too hard. Still get 3mpg too. Up over 35mph the mileage starts to drop. I'm not saying don't get a 300 but I'm not sure you'd need it.

For commercial stuff, tours and such, I would think twins would be better. A little redundancy and with the single I get some serious torque lean.

Jason

RIBS! · 19 October 2016, 23:50

I would definitely be interested in the 2014 Yamaha 300 if you decide not to pick it up. Is it a 30" shaft?
Please keep me posted on that.
I will be selling my twins.
If there is any interest in them they are:
2012 Evinrude Etech 150HP, shows approx 4,500 hrs on computer, have receipts showing new power head, injectors and lower end replace at approx 1,500 hrs. New Stainless prop with spares. No issues, looks and runs great.
2015 Evinrude Etech 135HP HO has approx 1,500 hrs on it. Issue with this one is 60 psi in cylinder 1 and 120 even in all other cylinders. Using it daily but if pushed will over heat.
I'm assuming needs rings in that cylinder but don't really know.
That also has a new stainless prop and spare.
Since i'm going single all controls, gauges, harness etc are available.
I also have lots of spares including cowlings, lower ends, starters, full blown engines etc for parts.
Let me know if there's any interest.

RIBS! · 20 October 2016, 00:11

You just gave me allot of good info.
I wasn't aware the 250 had a 4.2 L like the 300. I don't care about the top end as much as I do out of the whole so if they both are roughly the same torque then I guess i can now look at both options.
I was just looking at other 733 with an transom extension and i found a few with 250 hp and 25" shafts. Wondering if the extension allows for a shorter shaft?
It would be great to have that option as well since there are not allot of 30" shaft options out there for used motors.

jonp · 20 October 2016, 01:51

Wow a mix of opinions!!...for some real life boat tests look here at the performance of the df 250 on a 4.3 ton dive rib, click onto the performance tab and select the 9.5 m dive boat https://suzukimarine.com.au/outboard.../product/df250

Here's a performance test on another quite heavy sea legs rib with a df 200 same here click onto the performance tab
https://suzukimarine.com.au/outboard.../product/df200

Another dood place to see actual reviews on different outboard makes http://www.boatsales.com.au/editorial/engine-reviews/

Jon

tworotorturbo · 20 October 2016, 03:15

Quote:

Originally Posted by RIBS!

I would definitely be interested in the 2014 Yamaha 300 if you decide not to pick it up. Is it a 30" shaft?

Please keep me posted on that.

Yeah its a 30"

It's being sold by an acquaintance of mine who does a lot of work on ribs, pm me about it, I was going to get it but I can wait for a Honda to pop up. I'll deliver it to you at no charge if you give me a ride

RIBS! · 20 October 2016, 05:06

Thanks Jon for the Suzuki boat test links.
They are definitely confusing me even further unfortunately.
The heavy 9000 pound dive boats which are close to my 8000 pound fully loaded boat both show twin 250hp.
The heaviest single engine boat was just 4600 pounds and showed it only went 26 mph at 4000 rpms.
Based on those numbers my boat being double that weight probably couldn't even get on plane yet Jason in this thread and others have said they can do approx 30 mph at approx 3500 rpm on a much heavier boat than the Suzuki test.
You could see my confusion.
Any one have clarification on this.

Fender · 20 October 2016, 09:32

Quote:

Originally Posted by ncp

The 4.2L 250 hp only specs 87 octace. So, no.

verado 300-350 max HP on different fuel...

ncp · 20 October 2016, 19:42

Quote:

Originally Posted by Fender

verado 300-350 max HP on different fuel...

Running 87 in the F300 is always possible...but in suboptimal conditions, warm day, heavy load, the ecu/knock sensor could reduce your performance. Then, you're right back to basically the performance of a 4.2L F250

As I said, I would not pay more for a few mph of top end - sure enough, I found two examples of a 2 mph top end difference on Yamaha's website. Here's one example:

4.2L F250 http://yamahaoutboards.com/sites/def...-10-18_BAY.pdf

4.2L F300
http://yamahaoutboards.com/sites/def...-08-18_bay.pdf

And don't ask me why, but at 3,000 rpm, the F250 is getting better economy and speed (probably prop related)

jonp · 20 October 2016, 23:00

Sorry for being so dumb but my mate has a new Northbank 27 with a 300 Suzuki which we always put the lower octane unleaded petrol in, are you saying it shouldn't run on the lower octane as the dealers here tell us it should. It's only done 150hrs as we both have several boats which get used for different things ( Northbank for sword fishing at night).

By the way this outfit is 3 tons dry and over 4.5 tons on the trailor with a full tank. We cruise at 4500 rpm for 55kmh burning .5 lt per km.

I also drive a 7.7 Gemeni dive boat with twin 150 suzuki's for a local dive instructor but have to admit I have always preferred singles, less drag and faster handling. According to one of the most highly respected Yam dealers I've purchased engines from in my area, when I asked about putting twin yam f70's on a boat he claimed I would get around the same performance as a single 100.

Why is your boat so heavy? Looking on a zodiac site they state 1500kg or 3400lb.

Jon

ncp · 20 October 2016, 23:56

What does Suzuki say to use?

Yamaha specs lower octanes for some engines, higher octanes in others.

jonp · 21 October 2016, 00:13

Quote:

Originally Posted by ncp

What does Suzuki say to use?

Yamaha specs lower octanes for some engines, higher octanes in others.

Suzuki dealer says regular unleaded. Just checked Suzuki website and see nothing to state the need for higher octane this side of the pond.

Do Suzuki state higher in the US. I will check with another dealer but this 300 seems to run very smooth on what we are using.

We are told the higher octane fuels break down faster and not recommended to be left in boat fuel tanks for long periods of non use. It would be good if all dealers gave the same advice if they are selling the same brand.

If you have a link to using higher octane I will show it to the Suzuki dealer and ask why they haven't recommended it.

Jon

ncp · 21 October 2016, 01:02

Quote:

Originally Posted by jonp

We are told the higher octane fuels break down faster and not recommended to be left in boat fuel tanks for long periods of non use. It would be good if all dealers gave the same advice if they are selling the same brand.

Interesting...

Common wisdom over here (who know if it's right or wrong) is that because the octane does break down, start with the higher octane if your going to store it for long periods.