2 stroke v 4 stroke

[Pikey Dave]

Originally Posted by matt h

.................I might even get approval from PD on that one!!

Stranger things have happened

[jonp]

Most of us are going to say they preffer what they own or are using. I really don't care as I'm not loyal to any brand or type. Long life and resale value are what counts for me.

If out boards were all free with the condition you have to stick with it for 10 years it would be interesting to see where peoples choices might head.

Our rescue boat had twin verados but for a modern outboard they were so uneconomic we changed to twin 250 suzukis after 6months.

I've been on many boats with the latest 2 strokes and I've yet to go on one where thers no smell, yes it's nothing compared to the old carby engines but it's still there.

They are burning oil with the fuel where even 4strokes burning just petrol still have some smell as do cars. Anyone ever followed a car burning a little oil.

[BogMonster]

Stolen from a group on Facebook

[OSPREY RIBS]

Originally Posted by jambo

Hell you'll be starting the annual what's the best rib one shortly!!!!!!


Sent from my iPhone using RIB Net

[9D280]

Woah. Premix is the way to go. - No oil pumps to fail, no "cant lay it down on it's RHS, a perfect excuse to run at WOT for prolonged periods, no lard on the transom (I have an 83Kg 60Hp engine!)

What's not to like?

Originally Posted by spartacus

For me its also difficult to justify the added expense of a new mid-engine 4-stroke (which are difficult to come by second-hand too) for what is a recreational activity. It's not that I'm against 4-strokes, far from it, but a new Yamaha F70 is the best part of £7.5k.

Yep, and I have taken that to an extreme! (TBH rebuilding it was half the entertainment.....)

Originally Posted by Pikey Dave

Assuming that we are comparing modern 2 strokes to modern 4 strokes & not old tech carbed 2strokes, then that statement is b0110x quite frankly.

+1




OK, Joking aside.....

As a PREMIX 2T user I will admit it smokes like the proverbial lum when cold and on a slow downwind troll it does smell a bit, however It smokes a lot less than some I've seen through the years.

But how many do the "I'll add a bit more oil - just to be safe" trick? I have done the maths to make sure I get 50:1 in my tank every time. (you don't sling 600ml into an empty 30L tank - as the oil takes out a good half litre) OK, you are only 1.5 (ish) % over oiled, but then you top the tank up and oput in a wee bit more jsut to be on the safe side as you canlt accurately measure..... etc etc etc.

The only 2 times I have ever fouled my plugs was when I was running it in following the rebuild at a forced sub 2k rpm / 25:1 mix and the other when I went from Auchinstarry to the Falkirk wheel celebrations - along a canal at 4.5 knots! I really should have been running on the aux but wanted to get a feel for the displacement fuel consumption of the main.

Chaqu'un a son gout, as they say. (apologies to our French readers for the lack of appropriate accents there!)

[kaman]

All I can say is I'm glad motor manufacturers don't use 2 stroke engines in their automobiles
Says it all really. 😨

[jonp]

It's funny how many people think 4strokes are so much heavier than 2"s. I believe my yam f 70 is lighter than its equivalent 2"stroke cousins, not tha that really makes much difference. When you have boat owners of all different shapes and sizes what does a few kg in engine weight matter.

Also mentioned is being able to run flat out for extended periods, frankly this isn't good for any engine in my opinion. What engines are run in formula 1 cars and bikes ? Aren't these run at high rpm.

[9D280]

Originally Posted by jonp

It's funny how many people think 4strokes are so much heavier than 2"s. I believe my yam f 70 is lighter than its equivalent 2"stroke cousins, not tha that really makes much difference. When you have boat owners of all different shapes and sizes what does a few kg in engine weight matter.

You have just put some fact behind another ribnet "standard myth".... Yes, back in the early days they were generally well heavier when compared Hp for Hp to a 2 cyl premix 2- stroke, and like all tech they have imporoved.


Why the weight concerns? - coz transoms all have "max limits"...... If I hung a 4- stroke (OK, maybe leave the new Yams out of this statement!) on mine I would rip the transom off..... or more likely swamp the baot as I donlt have long toob extensions to support it "off plane".

That's why it's important!

Originally Posted by jonp

Also mentioned is being able to run flat out for extended periods, frankly this isn't good for any engine in my opinion. What engines are run in formula 1 cars and bikes ? Aren't these run at high rpm.

And they do...... Motorbikes are designed with lightweight pistonsetc, and F1 card only really need to survive at high RPM for a few hours... then they get rebuilt! Drag racing engines take that to the extreme - as long as it survives 30 seconds or so at WOT they are happy!

[jonp]

It's not only the small Yam f 70 which has dropped the kgs, the latest 130,175,200 etc are all now much lighter. When it comes to weight on transoms once again you could have someone standing at the back with a rod in their hand weighing 60 kg or 160 kg, or even two people. Depending on the prop the torque can also be very different on the transoms with the same hp.

When I used to compete in moto x those with 2 strokes did rebuilds quite regularly while the 4"s just kept plugging on.

A mechanic mate who maintains a large house boat business in Sydney tells me how they get up to around 9000 hrs on the 4's before they replace them.

In this part of the world the serious offshore anglers often head out 100 km or more in search of tuna. The demand for economical reliable outboards is what has turned the highest percentage of selling outboards what it is today. I did ask what hours people are putting on their engines which nobody seemed willing to post.

I had the pleasure of a 4 day fishing trip with a very well known TV fishing show. The company owned 8 boats, 4 of which had twin modern 225 2strokes. First day of my trip we had one engine literally blow up, metal came out of the exhaust. The 80 k run home on the single engine which also developed problems was a little disappointing.

With only one of the large boats in the fleet running my trip was over. According to the skippers the gear boxes were only lasting 500 hrs and power heads a max of 1000 hrs. This wasn't much of an issue as the outboard company which sponsors the show replaces the engines with new. I would hope the manufacturer has now got things a little more under control.

My local outboard dealer is currently having issues with this same company in regards to warranty issues and is trying to drop them from their outboard sales as the company is not wanting to honour the extended warrantee.


Jon

[9D280]

Interesting real world data.

Perception is also a good "stats bender". I use my own clamshell as an example.
Most people old enough to remember them - what were they notorious for? - Overheating & killing their top piston. So why did I choose one? The main reason (other than availability & budget) was the weight. My transom will only take 110 KG, a "bulletproof" Yam 60 auto mixing 2-T would have given me no capacity for an aux.


I got an engine that having dismantled it turned out to be a lot older than the cowl's paint job suggested. I found stuff that acording to the microfiche implies I had a late 60s (i.e very early) one. And guess why I rebuilt it..... yep, it destroyed it's top pistion!

So, I researched it and found a few changes:

Cooling - the entire Inlet side of the cooling system had been changed. The down side is it is over cools at idle so runs a bit rough down there, but I don't spend long enough "trolling" to care about that. Also the tell tale outlet was changed to about half the size (to direct a bit more water past the hot bits!)

Self destruct pistons - well.....
The new pistons inside my engine are a god few grams lighter than the originals, and also have 2 rings instead of three on the original. The spark advance has (officially - not just me tinkering!) been retarded by a few degrees (it was the pistons being pushed into the exhaust port seems to have been the main problem - and guess how mine died!) . the lighter pistons allow it to rev about 500 rpm or so higher than the 1960s version thus restoring the power lost by retardeding the spark.

Another famous fail was the standalone auto mixer. Guess why I premix!

I'm led to believe the newer vintage Clamshells were actually quite reliable - and certinly were a vast improvement compared to the older generations. .......


But all people rememeber is "they overheat and destroy the top piston...."


Which is Why frequently I type here "research - donlt jsut go by the rumours.


TBH I'd love a nice new quiet lightweight Yam on the transom & leave the dinosaurs as restoration projects.... but don't have that sort of cash lying around!

[jonp]

Totally agree those old yams are solid workhorses, unfortunately they don't meat the emission rules under the new standards. You also can't use the modern 2strokes on most freshwater dams as these are used as our drinking water.

[Phil M]

Originally Posted by jonp

It's funny how many people think 4strokes are so much heavier than 2"s. I believe my yam f 70 is lighter than its equivalent 2"stroke cousins, not tha that really makes much difference.

The gap has really closed up. My Merc 115 4 stroke is 163kg (dry weight, long shaft), which is the lightest engine I could find at the time. The next lightest was the 115 Opti at 170kg, then the Eninrude and twatsoo at 177 and 178kg. I'll admit, the heaviest in the range is a 4 stroke though. The Honda at a monstrous 217kg. The new merc is about the same weight as a 1986 Evinrude 120 loop induction (according to the best info I found).

I chose the 4 stroke on weight, but it would have been a 2st had they been lighter. I do like the quiet and greatly reduced smell though.

Phil M

[Orwell boy]

Not really too qualified to comment on this one but for me ,I was just chuffed to get out of the old inboard scenario ,especially when you look at the whole picture ,my ally highfield 5m with 90hp four stroke honda(@163kg) sits on an unbraked trailer ,and that's a big bonus in my book ,only real concern was when somebody suggested it was a Honda Jazz engine on its side ,I had to question whether in my early fifties I was really ready for a Honda Jazz .. (sorry only 25 hours so far)

[jonp]

Originally Posted by Orwell boy

Not really too qualified to comment on this one but for me ,I was just chuffed to get out of the old inboard scenario ,especially when you look at the whole picture ,my ally highfield 5m with 90hp four stroke honda(@163kg) sits on an unbraked trailer ,and that's a big bonus in my book ,only real concern was when somebody suggested it was a Honda Jazz engine on its side ,I had to question whether in my early fifties I was really ready for a Honda Jazz .. (sorry only 25 hours so far)

Those were a great engine, I sold a boat with a 90 Honda with over 5000 hrs and there are plenty with way more than that on them from the commercial side. You often find engines that run longer hours per day will out last the ones that do a short trip then allow the engine to cool before blasting off on another short trip. The Honda jazz was an extremely good little car, the body normally gave up the ghost well before the engine.

Jon

[jeffstevens763@g]

soon be more choice mercury have redeveloped the diesel outboard took the 225 hp v6 optimax 2-stroke resulting in a 180 hp diesel @ 230 kg for military and commercial use at the mo.

[Chris]

Here's an interesting comparison... and again proof that you just cant beat the E-TEC...

https://www.youtube.com/watch?v=tZvIw83uZgY

[Chris]

Originally Posted by jeffstevens763@g

soon be more choice mercury have redeveloped the diesel outboard took the 225 hp v6 optimax 2-stroke resulting in a 180 hp diesel @ 230 kg for military and commercial use at the mo.

Not sure that a spark ignited 2 stroke diesel is the way forwards, without the high compression there really is not much benefit in diesel... However as the Navy don't like to carry petrol on board their ships, needed something to fill the gap.

[A1an]

Originally Posted by Chris

Here's an interesting comparison... and again proof that you just cant beat the E-TEC...

I'm not dissing the etec but there is no mention of the props on each engine.

I notice the etec 40 has a nice shiny stainless job on it.

[sorabain]

Originally Posted by Chris

Here's an interesting comparison... and again proof that you just cant beat the E-TEC...

guess which specific brand this outfit sells?

[Chris]

Originally Posted by A1an

I'm not dissing the etec but there is no mention of the props on each engine.

I notice the etec 40 has a nice shiny stainless job on it.

Yes the E-tecs ship with a stainless prop. I guess just another tick in the box for E-TEC

However interesting to note that all the outboards give similar top end speeds other than the e-tec 30, suggesting they are propped correctly.