Logo
FULL SITE MENU

2or4stroke please Help

C

Crestcutter

New member
Hi sorry to bug you,I cant find out anywhere ,but here goes , im thinking of buying a motor but I dont know if it is a 2or4 stroke model neither does the guy who is selling it,It Is a 2002 ,115 mercury outboard serial number, OT511574,Please help ,and keep up the good work best wishes ,Crestcutter:eek:
 
Re: (2-STROKE)

It's a two stroke, And It should be oil injected "when it was new".;)

One way to know if it's a four stroke is it would have had an oil filter like a car does, And normally the decals on the cowling would say it also from stock.

Your service manual part number from mercury marine is 90-830234R04, It covers the 75/75 MARATHON, 75 SEA PRO, 90/100/115/125 - 65/80 JET HP's.:)

Your engine info is a 2002 MERCURY SPECIAL DECALS SALTWATER 115 EXLPTO SW (4 CYL) Carburetor, Model # 1115422ZY.:)
 
Re: (2-STROKE)

Thanks heaps ,Nice to know!now to research this engine ...Here goes.....Any tips about this motor appreciated ,thanks again,Love this Site!!
 
The 115/125's were Merc's "mid-sized" 4 cylinder engines for a good number of years and they were extremely popular. They were no more or no less durable than the other major mfg's offerings of the time. They had very good carbs and maybe the best ignition system in the business. They were also a pretty "gutsy" motor.

They do have one quirk for people not familiar with them - they employed a (often called) 2+2 system (I believe it's a Yamaha invention) where they run on two cylinders at idle and lower rpms, then all 4 cylinders "kick in" once you get above 1800-2000 rpms (give or take). In theory this saves some gas so they can claim to be a little more efficient at lower rpms than other 2 strokes, but I suspect the savings are so minimal as to go un-noticed (if you really want to save gas at lower rpms, install a kicker motor and keep the big one shut down).

That cross-over (both going from 2 to 4 then back from 4 to 2) can seem a little "violent" if you are not used to it, but it is totally normal.

These were routinely packaged with 16-18 foot runabouts for those who wanted the "psychological" performance increase over 90 which often came with the basic package.

I say psycohological because in actual practice a 115 is only minimally quicker than a 3 cylinder, 90 horse on a given rig (about 3 mph faster at top end and without looking at the speedo or gps I don't know too many people who can tell the difference between 35 and 38 miles per hour on the water). Where the 115 significantly excels is in the low end torque (in comparison to the 90) - greater displacement and the extra cylinder means the boat will get out of the hole quicker - particularly desireable if the boat is used for watersports.

Having said all the above, I would have zero issue hangin a 115 Merc off my transom if it presented itself - it just wouldn't be my first choice in that particular horsepower range, but it is a "solid" engine...
 
Rigger's rule of thumb - always hang 80% of the boat's max horse capacity off the transom in order to get the boat to perform "as it was designed".

Underpowering a rig can be as bad as over powering but for different reasons.

So I would start by checking your coast guard plate to see what the max horsepower for your rig is.

If it's say 120 horses - 120 X .8 = 96 (which would be the optimal horsepower).

So going with a 90 would be pretty darn close. If you opted for the "next motor up", which in the case of Merc has only been the 115 for a good few years now (they used to produce a 100 horse), as noted in my earlier post, you only gain a few mph.

On the down side, you gain 80 pounds hangin off the back (the 115 is heavier), and at full throttle it would burn about 2.5 gallons more per hour to give you that 3 extra mph - plus it would burn a little more gas at all speeds just because the displacement is greater.

But if you really need a superior hole shot (ski, wakeboard etc), then the extra weight and higher fuel consumption is the trade-off.

Now say your rig can take a 150 horse max. In that case the 90 might not be enough. The boat just plain wouldn't work the way it was designed and you would always be disappointed. A 150 max rating would require (150 x .8 =) 120 horses. In that case you would have two main choices - the 115 or 125 (same engine in all respects except for the horsepower), in which case you may as well go with the 125 since it weighs the same as the 115 - it would burn a bit more gas, but the 10 extra horses would offset the extra weight you are carrying, OR

You say "what the heck" and go with the 2.0L V6 135 - which in my opinion is the best V6 Merc ever produced. It's just a sweet motor that was almost "born" to crank out 135 horses with tons of torque.

And personally, in that 90-150 horse range I really would skip over both of Merc's 4 cylinder options (115/125) - if you can get away with the lower horsepower go with the 90 (which is exceptionally well built and is quite possibly the most popular motor on the planet) - but if you need some more guts, and can safely rig it, jump up to the 2.0L 135 - a very sweet engine..
 
Thanks again for your insight,You make very good sense,my boat Im sure is rated to 115Hp im currently running a 85 mercury,which gets along nicely ,At 3/4 to full throttle,So do you think the 90 Hp 4stroke ,Maybe 100Hp 4stroke[,If i can get my hands on one,lol] Or 2stroke which way would you go ,Thanks Again for your Help, your a legend,So appreciated,I never knew that about boat and motor before. :] Very Interesting,Thank you
 
Back
Top