Which is more reliable Merc. 2 or 4 stroke?

Migmatic

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Joined
Feb 21, 2009
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3
Newbe here.
I've run an 1986 mercury 2 stroke, 6 cyl, 90hp,..."Tower of Power".

I never liked the idea of a 2 stroke..., too many chainsaws, and lawn mowers that let me down,...BUT I have been pretty happy with this unit.

I drive it pretty hard on the Great Lakes. It has not let me down in a tight spot, (been in many) and so reliability to start and go is VERY important.
I have rebuilt the powerhead twice and lower unit was replaced after a prang with an underwater wreak. I rebuild them myself but have a shop do the machine work. My merc mechanic said after the last rebuild, that that was it, if she goes again get another engine. Well she "blew" last year.
Hey, it's 22 years old!!
He wasn't particularly taken by the 4 strokes and believes when it comes time to rebuild those a lot of owners will get the estimate,(valves,cams,springs,time, etc.) and simply chose to make them a boat anchor!

This is an engine that I would like to last for at least 20 years with good care, (I drive it hard but I baby it, my life depends on it!).


I am now in the market for another 90 merc. What should it be 2 or 4 stroke?


I am somewhat environmentally aware but the newer 2's are much more efficient, etc.
(one issue I have with the new 2 stroke is that it is a 3 cylinder affair, I drove a friend's 3 cylinder 75 merc. which was about 6 years old,...HORRIBLE,... it was a lumpy, rough running, noisy affair which felt like it was going to cut out at idle!!).

Any thoughts? Any experiences?
 

mthieme

Captain
Joined
Oct 6, 2007
Messages
3,270
Re: Which is more reliable Merc. 2 or 4 stroke?

None of my Merc 2 strokes have ever let me down.

You had a 2-stroke lawn mower ????? never seen one of those.
 

Migmatic

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Feb 21, 2009
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Re: Which is more reliable Merc. 2 or 4 stroke?

Yup! Lawnboy,...worst nightmare I have ever had;... plastic carb!!!!,....awful (the commercial units are supposed to be better,...hmmmm!)

One point I did want to mention was I run early spring to late fall, in fact I run it into winter time so freezing temp. is always a concern,and so far leaving lower unit down avoids problems, (but once I start being a little ice-breaker,...I pull the boat). I don't know if this is a bigger problem for the 4 strokes?
 

Yepblaze

Lieutenant Commander
Joined
Jun 1, 2001
Messages
1,686
Re: Which is more reliable Merc. 2 or 4 stroke?

Lawnboys were made by OMC.
 

Navy Jr.

Senior Chief Petty Officer
Joined
Sep 14, 2007
Messages
738
Re: Which is more reliable Merc. 2 or 4 stroke?

None of my Merc 2 strokes have ever let me down.

You had a 2-stroke lawn mower ????? never seen one of those.

Toro sold a bajillion of them. The 2-stroke engine on our Toro was made by Suzuki. Still using it after 24 years.

Regarding reliability of Mercury motors, who really knows for sure? Most motors are designed by computer, and their parts cut by computer, so that tolerances are very close. To me, then, the variable would be engine operation and maintenance.

Most of the new Mercs today come with a 3-year warranty (now 5-years under a promotion they've been running since 2008). That should say something.
 

philbur

Seaman Apprentice
Joined
Aug 13, 2008
Messages
41
Re: Which is more reliable Merc. 2 or 4 stroke?

IMHO...4-Stroke, 4-Stroke, 4-Stroke...

As a mechanic I absolutely would go for the 4-Stroke due to several points...\
1: the longevity of the internal components...(less stress)
2: the relative ease by wich the engine can be stripped down (if needed)
3: they are a lot quieter...without exception...and really DO emit less stink.
4: Most importantly...mordern 2-Strokes are a wonder of engineering and are very well put together....but they rely on fairly high-level computerized engine management systems to accomplish this...all of which are critical to even the minimum operations. If a single sensor fails to operate correctly then you are stuck...no way to remedy a failure code without the "SCAN TOOL"....and if you have blown up engines before then you would benefit from the more robust internal construction of the 4-stroke. When a 4-stroke DOES grenade it is less catastrophic than a similar failure on the 2-strokes...and in the event of valvetrain failure it is usually a burnt valve or broken chain/belt/tensioners....all of which are easily avoided by proper maintenance and reasonable operating habits.

In short...there are arguments to the contrary...of course...but if you want an engine you can count on in any condition....for a long time....and need to be able to service it yourself...then I would go with the 4 Stroke.
Talking to a service shop about which system would be cheaper and easier to rebuild if you blow one up is kind of concerning.....as you have already had to rebuild the 90-horse several times it should be a hint that perhaps your operating methods and/or the argument about which system is more reliable has already been demonstrated...right?....(said with humor).
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: Which is more reliable Merc. 2 or 4 stroke?

Lets analyze Philbur's comments:
1: the longevity of the internal components...(less stress).
100 HP is 100 HP. It is delivered by a piston, rod, and crankshaft whether two or four stroke. Longevity is also very speculative since four strokes are just kids compared to the amount of time two strokes have been around. Only time will tell whether your contention is accurate. More parts to wear would tend to indicate quite the opposite is true.
2: the relative ease by which the engine can be stripped down (if needed)
This is a rediculous statement. A two stroke has far fewer parts.
3: they are a lot quieter...without exception...and really DO emit less stink.
Another rediculous statement. At wide open throttle two and four strokes from the same manufacturer are nearly identical in noise levels. Go to Yamahas web site and check a few.
4: Most importantly...mordern 2-Strokes are a wonder of engineering and are very well put together....but they rely on fairly high-level computerized engine management systems to accomplish this...all of which are critical to even the minimum operations. If a single sensor fails to operate correctly then you are stuck...no way to remedy a failure code without the "SCAN TOOL"....and if you have blown up engines before then you would benefit from the more robust internal construction of the 4-stroke. When a 4-stroke DOES grenade it is less catastrophic than a similar failure on the 2-strokes...and in the event of valvetrain failure it is usually a burnt valve or broken chain/belt/tensioners....all of which are easily avoided by proper maintenance and reasonable operating habits.

Get real here Mr. Mechanic. When a four stroke grenades it is just as likely to stick a rod through the block as a two stroke. And are you telling me a four stroke doesn't have a sophisticated computer controlled engine management system without sensors. Where in heavens name have you been wrenching? Geez the Suzki I have on my pontoon has a very sophisticated ECU, EFI, coil-on-plug, and a bunch of sensors. And if a four stroke happens to be an interference engine, tossing or breaking a timing belt or chain does cause catestrophic damage as valves collide with pistons.

As for routine maintenance a four stroke requires periodic valve clearance checks and adjustment, oil and filter changes, belt condition and tension checks -- none of which is necessary on a two stroke. Lower units are lower units so that's a push.

You also state that four strokes emit less than two strokes. Current technology on two strokes are every bit as clean in some cases cleaner than four strokes.

Your rebutal please!
__________________
 

Migmatic

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Feb 21, 2009
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Re: Which is more reliable Merc. 2 or 4 stroke?

Oh dear!!!
Philbur/Silvertip,...I see both of your points very clearly and though not a professional marine mechanic my thoughts about less stress on 4 strokes vs 2 strokes seems valid.
I do get concerned about how easy it might be to tear it down. My thoughts about fewer parts on the 2 stroke would make it easier to rebuild than the 4 and less fiddly bits to replace,... bushings, bearings, rockers, gaskets just multiply on the 4.
Quieter,...4 stroke seems to have it beat,... but I haven't run my brother-in-law's 90hp 4 at full bore, (hey, he is my Brother in law---if I toast it I'll never hear the end of it!!).
As for computerized operation, whether it's 2 or 4 I'm sure they both have their fair share of "black boxes" most of which if they were like my 1986 are virtually impossible to test (the 2 ignition boxes), that are darn expensive ($500.00) to replace. I just hope they last a LONG time or have fewer problems.
Scan tools,...oh I hope not, I'll have to check that out.

I have a car that has an interference engine,..boy I'm up on timing belt changes. Break that and for the car and age,...well it's a right off, I will check. And 10 years down the road (water) I would be very concerned about that. The cost of Merc parts are NOT cheap, (one oversize piston for my 1986 was $200.00+, multiply that by 6 and you know where that engine is headed!)
Sure the 4 seems better from an environmental standpoint, (no total loss oil like the 2), but I am sorry if it came down to that vs reliability, ease, survival, etc. then environment takes a back seat.
Mind you I go through $300.00 in 2 stroke oil a year,(only SLIGHTLY richer than recommended), so I would save that.

You guys have given me more to think about, keep it coming!:D
 

OldMercsRule

Captain
Joined
Nov 30, 2006
Messages
3,340
Re: Which is more reliable Merc. 2 or 4 stroke?

Never owned a four stroke outboard and don't plan too unless the Communists outlaw me black boat anchors.

Yer 1986 is newer then any of me towers, (my newest one was a 1981 115 at the crank very similar to yer prop rated 90). I prefer the older distributer fired girls meself.

I bought a low hour 1968 1250 in 1985 or 86 and ran it hard and long to 10/31/2005 when me son torched #3. I have two 1969 1000s the first one I bought in 1996 a perfect low hour fresh water engine. I know it is a virgin, ('cept one time thru the carbs). BTW the 1968 1250 was a virgin including the carbs as well, n' prolly had 5000 hours of it before she blew, (a guess).

You can tell if the silverblock inlines, 1972 and older are virgins as they have wire nuts like aircraft engines. I bought a 1979 115 in 1999 that I have run hard and put away wet without any problems at all. I also have other inlines that have rarely let me down.

The key is watch the tell tale fer cooling problems, n' run 'em out of gas when ya leave 'em fer a bit. Change impellers, gear oil, filters n' fuel pump diaphrams n' fog 'em fer the winter.

The four stoke stuff is nice if ya wanna be in style n' like to spend lots of time maintainin' 'em but they are all heavy POS that never get infront of my old 30 to 40 year girls.

Pound fer pound dollar fer dollar ya can't beat old inlines in FRESH water, salt is another kettle of fish.

Talk to me about the four stokes in 20 more years and I bet you will be hard pressed to find virgins like the ones I own and run.

Me overpriced $.02. JR
 

just_crsn

Seaman Apprentice
Joined
Feb 29, 2008
Messages
49
Re: Which is more reliable Merc. 2 or 4 stroke?

:D:D Sometimes you cant teach an old dog new tricks. Well, four strokes are the future of boating.....like or not. The new 2 stroke direct injection are as heavy as 4 strokes and as complicated. They are both computer controlled. The new DI 2 stroke is the new technology and will have to prove their worth because at this moment they are as expensive or more so. For the old 2 stroke, sun is setting and will be as difficult to get parts for.......because the environmental concerns will force them out of the water.At this moment in time 4 stroke have been around for decades and have proven themselves. I have owned 2 strokes but have seen the light and I'm a convert. I will never buy another 2 stroke. Just another opinion.....:D:D
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: Which is more reliable Merc. 2 or 4 stroke?

Since nobody apparently took the time to look at Yamaha noise levels, I will do it for you. By the way, don't you find it a bit odd that Yamaha in the past had listed dB (noise levels) for all their two strokes but they suddenly quit doing that for some of their later four strokes? On an Alumacraft Tournament Pro with a 175 2-stroke, the engine showed 79 dB @ 3000 RPM and 92 dB at wide open throttle. A four stroke showed 90 dB at WOT and 77 dB but on a different engine as their 150 4-stroke did not have any noise levels shown. So much for quiet. Perceived noise levels are affected by the type of sound and really have no bearing on the actual noise level. A two stroke sounds different than a four stroke but that does not automatically make it a noisier engine. A couple of years ago I was picking up a motor at a small dealer in northern Minnesota. I got to nosing around the shop and noticed a line of three cylinder four strokes on the floor. I don't remember the exact number but it was in the 8 - 10 range. Hmmmmm I thought. Wonder what this all about. A closer look revealed that every one of these engines including a v6 on a bench had a hole in the block. The only other engine being worked on was an old Johnson V4 that had obviously been around the lake a time or two. When I questioned the owner about the engines I was ushered out of the shop. So much for robust internals. As for emissions, it's pretty common knowledge that the E-tec is a very clean engine. Just wait until the outboard industry (two or four stroke) are required to add catalytic converters. The I/O industry is already having to look at this.
 

WrenchHead

Petty Officer 2nd Class
Joined
Feb 15, 2009
Messages
120
Re: Which is more reliable Merc. 2 or 4 stroke?

Look at the piston driven aircraft and automobiles -- 4-stroke and very reliable. Years ago when weight was important 2-cycles were for boats. Not the case anymore. I have owned a Merc 2-cycle and now a Merc 4-cycle. The 4-cycle starts like a car engine and idles smoothly and quietly like a car engine. 2-cycles crank and crank and sometimes they start :). How a 2-cycle runs is beyond me -- sucking gas and oil mixture into the crankcase to lubricate the rod and from there into the combustion chamber to drive the piston. With a design like that I'm surprised they run :)
 
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