Best for Aerotec - Tohatsu 18 2-st or Suzuki 20 4-st EFI?

Fenlander · 20 February 2016, 12:04

Following on from my thread http://www.rib.net/forum/f36/suzuki-...tml#post706941...

I've had a bit of a lateral thought...

Forgetting any cost difference... on an Aerotec (or any sib of a similar size really) would you prefer the attributes of a new model Suzuki 20hp EFI 4-stroke (44kg) or an as new as possible (assume mint) Tohatsu 18hp 2-stroke (41kg)??

willk · 20 February 2016, 12:29

I'd be asking some questions about torque - no idea myself, but I'd be asking. The NACs always say there's "no replacement for displacement" but I'm not sure what 30cc difference will make to your rig? 3hp wouldn't seal it for me until I was sure.

The Suzi has to be miles quieter - nice when pootling. Same with fumes.

I'd view the "lean burn" thingy with a cynical eye. On the bigger engines, it seems to work best when running continuously in a certain rev band. Not the typical sibbing trip!

Will the Suzi fit in your packing plan?

Fenlander · 20 February 2016, 12:35

The Tohasu 18 exterior dimensions more closely match those of my Mercury 15 than the bloaty Suzuki... plus of course keeping to a 2-stroke means the choice (broadly) of "any way up you like" packing.

The Suzuki has a (as with modern cars and large outboards I guess) map in its little ECU that enables it only to go lean when at constant throttle settings with normal fuelling when opening up.

The Mrs (my main crew) would appreciate the quieter engine.

Stevem · 20 February 2016, 13:38

I'm loving my 25 and would not swap it for an 18. In the future I may go for a Suzuki 20 though!
Is the 18 a noticeable difference to a 15, anybody?
Then there's the advantage of a quieter engine less fumes as you and Willk have already mentioned. This would get the vote for me.

jeffstevens763@g · 20 February 2016, 16:53

The lean burn system predicts fuel needs as required from low speeds through to crusing speeds fuel ratios for normal engines 14.7:1 lean burn up as far as 19:1 fuel consumption is very good in my expeariance 25hp & 90hp.
Consider evinrude etec maybe.
Tohatsu make the lower hp Mercury engines is the 18 tohatsu an uprated 15 if so up rate and keep the Mercury possibly?

Fenlander · 20 February 2016, 19:04

Probably right that if I'm going to swap away from a known reliable mint condition engine it's not worth doing unless I gain the full 5hp up to the 20hp... and make that move to a bang up to date new 4-stroke model.

Jeff the Tohatsu range is different to some in that the 6/8/9.8 are all related with the same weight then the 9.9/15/18 are related with the same weight so the 18 is good "value" weight wise compared to the 15. However those particular models don't mirror the UK Mercury/Mariners of the same era as my Mercury (mid 2000s).

There is no upgrade to my existing 15 available (unless you were a race tuning specialist).

Weirdly though in the places they are still sold Mercury offer a 15 and a 15 Super 2-stroke. The 15 is a 262cc looking identical to my old Mercury 15 and the 15 Super looks just like a Tohatsu 18 with the same capacity as the 18 at 294cc. I guess if you had a current model Mercury 15 Super you could find out the Tohatsu 18 parts required to upgrade it to an 18.

Poly · 20 February 2016, 19:18

Quote:

Originally Posted by Fenlander

Following on from my thread http://www.rib.net/forum/f36/suzuki-...tml#post706941...

I've had a bit of a lateral thought...

Forgetting any cost difference... on an Aerotec (or any sib of a similar size really) would you prefer the attributes of a new model Suzuki 20hp EFI 4-stroke (44kg) or an as new as possible (assume mint) Tohatsu 18hp 2-stroke (41kg)??

I thought (from memory only) that the Tohatsu 18HP was lighter than that? If I was keeping it on the boat I'd go for the Suzi... If I was lifting it off the even small weight saving, and the flexibility of storage position on the 2 stroke would certainly make it a possibility.

Fenlander · 20 February 2016, 19:46

Yes every couple of Kg helps when setting up each use. The Tohatsu figure is from their website and 41Kg isn't too bad because I think most folks think it's nearly a 20 and then they'd be into 48-52kg in any other brand.

C-NUMB · 20 February 2016, 19:55

Quote:

Originally Posted by Fenlander

Yes every couple of Kg helps when setting up each use. The Tohatsu figure is from their website and 41Kg isn't too bad because I think most folks think it's nearly a 20 and then they'd be into 48-52kg in any other brand.

The tohatsu is not bad on Hp. Its tested on the shaft 20-21 hp, still considered very reliable.

jeffstevens763@g · 20 February 2016, 21:28

Quote:

Originally Posted by C-NUMB

The tohatsu is not bad on Hp. Its tested on the shaft 20-21 hp, still considered very reliable.

How much loss at the prop if the 18tested on the shaft how much nearer will it be tested at the prop to the 15 he has already OMO but 5hp will be a lot more noticeable than 2 possibly 3hp.having said that!
There's an interesting YouTube trial done in Russia of a 20hp EFI and a 15hp carb suzuki's with 3.80 m suzimar boats I was very surprised how near they were worth a look!
It's a tuff choice given space David has and a few kilos can make manageable difficult.

Fenlander · 20 February 2016, 21:45

A layman has to accept the makers HP figures and I can only agree 5hp at a 33% power increase over my 15hp should be noticeable.

As a matter of interest on SIBs of a medium size range I've come to the conclusion ideally you need 5hp per person for decent on the plane performance. We are always two up and often three... occasionally four. It does annoy me when taking that extra 4th person (guest) out the current outfit is less than impressive and it's my hope one of the 20hp positives to be weighed against... err its weight... is achieving that crew + guest performance.

kaman · 21 February 2016, 01:19

Without reading all of the aforementioned discussion I would say go for the 4 stroke all day long☺
I've never looked back on either of my road motorbikes, trail bikes or outboard engines after making the transition from 2 stroke .
The extra torque and less revs = 😊
Similarly I would not go back to owning a petrol car having owned several tasty souped upTurbo Diesel marque's😛.

C-NUMB · 22 February 2016, 09:29

Quote:

Originally Posted by jeffstevens763@g

How much loss at the prop if the 18tested on the shaft how much nearer will it be tested at the prop to the 15 he has already OMO but 5hp will be a lot more noticeable than 2 possibly 3hp.having said that!
There's an interesting YouTube trial done in Russia of a 20hp EFI and a 15hp carb suzuki's with 3.80 m suzimar boats I was very surprised how near they were worth a look!
It's a tuff choice given space David has and a few kilos can make manageable difficult.

My bad, should have written prop shaft, because that was where from the power was measured. So its a strong little beast. For sure its more noisy than modern engines, but otherwise would think a optimal match to an aerotec.

Fenlander · 23 February 2016, 11:01

Oh well decision made (which I'll report on in my engine thread... http://www.rib.net/forum/f36/suzuki-...ons-71122.html ) to go for the Suzuki 4-stroke. I really like the Tohatsu 18 but ideally wanted new and that was a little complex for a Tohatsu given current regs!

jeffstevens763@g · 23 February 2016, 11:16

Quote:

Originally Posted by Fenlander

Oh well decision made (which I'll report on in my engine thread... http://www.rib.net/forum/f36/suzuki-...ons-71122.html ) to go for the Suzuki 4-stroke. I really like the Tohatsu 18 but ideally wanted new and that was a little complex for a Tohatsu given current regs!

enjoy David
you wont regret it its the best choice going for the 20 hp of any make you will have plenty of power to cover all your needs just hope getting it in the car works out OK

cheers

chipko · 23 February 2016, 14:48

Agreed. Hope you will be as pleased with yours as we have been with ours.

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Fenlander · 23 February 2016, 15:37

Thanks Chipko... remind me... did you make that wonderful trolley?

Max... · 23 February 2016, 16:03

Wooohhh, Judas!

How dare ye abandon the world of 2-smokes!

I never would have thought it of you David.

But...in seriousness if there is a small 4 stroke to get that must be the one.

chipko · 23 February 2016, 16:05

Well not make, but an adapted cheap dolly off eBay.
It doubles up to either move boat and motor on launch trolley or move engine on its own.

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Fenlander · 23 February 2016, 19:30

>>>How dare ye abandon the world of 2-smokes!

Well yes indeed. Funny thing is the more I looked into this Suzuki 20EFI the more I realised the ideal SIB engine was a last of the Mariner/Mercury/Yamaha 15hp 2-stroke models.... and that I had a minter one of those in the garage already.

But I was on a downhill slope with no brakes so it's happened anyway!

Chipko is it based on one of these... Metal Caravan Trailer Dolly Mover - H-Duty Black - For Boat - Jet Ski - Utility | eBay

That's interesting as I was wondering about making something that would both take the outboard and alternatively hook into the bow handle of the Aerotec so it was held off the ground then when taking it along the road for a distance you are not trying to lift with your hand awkwardly behind you and pull as well.

Something similar would do the trick.