4 stroke vs 2 stroke power

[Prof T]

Going to pull the trigger and replace the old 2 stroke 90hp evinrude on my 19 ft aluminum sea nymph with a new 4 stroke. With the old motor, no problem getting over plane and running about 36 mph

 

I'm wondering about the power rating of new motors. A buddy replaced a  2 stroke 15 evinrude on his duck boat with a 4 stroke 15 Honda, Turns out the new motor doesn't come close to the pop the old one had. I've heard the same about larger motors....the new 4 strokes don't measure up to the older 2 strokes for snap and get over plane torque.

 

What are the opinions of guys here that have done it or know someone who has. Stay with the same to get the same, or need to go larger to maintain? Difference in repower price between a 90 and a 115 is about $900. (Boat's rated for a 140)

[rolmops]

2 strokes will always accelerate faster than a 4 stroke. This is simply because it is every second stroke a power stroke against every fourth stroke a power stroke. Add to that the extra weight that a 4 stroke has compared to a 2 stroke and the 2 stroke will get you out of the hole faster than a 4 stroke. If you are willing to give up some hole shot you will be rewarded with great fuel savings with a 4 stroke.There is also the pollution that a 2 stroke produces compared to the relatively cleaner 4 stroke. The e-tech is the best of 2 wordls.That is why e-techs are so popular (and expensive).

[stoneam2006]

Just another angle to look at.(I am a dirtbike rider) 2 strokes are easier to work and and less costly to fix than a 4 stroke. Valve work is something that most guys can't do at home compared to a new ring on a pistion on a 2 stroke.

Side bennifit is 2 strokes smell better

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[rolmops]

Ah, the smell of 2 stroke in the morning....

[stoneam2006]

Ah, the smell of 2 stroke in the morning....

Wish I could like more than once.....especially with quality oil like klotz

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[Bozeman Bob]

The motors are rated at the prop,2 or 4 stroke. A 2 stroke will rev quicker but does not have the same torque/power as a 4 stroke. It does weigh a bit more but not enough to make so big a

difference that you need to go from a 90 two stroke to a 100 four stroke to get the same top end. The biggest thing is to get the correct prop so the engine peaks out a couple hundred rpm under the rated number with a full load on the boat. Or empty hits the redline. I would go 4 stroke all day long if I was buying a new outboard. Your minimum hp should be 65% of the max rated hp of the hull. I didn't do the math on yours but I would spend the extra 900.00 and go for the 115,you will be happier in the long run. As far as rebuilding a 2 vs 4 stroke if you follow mfg scheduled oil changes you will probably never have to rebuild that 4 banger. That would be the least of my worries. BTW raced MX for 15 years and 2 strokes needed rings/pistons every 15-40 hours of riding time depending on if it was a 125 or 250. The Yamaha 4 strokes would go for 2 - 3 seasons without anything but oil changes and that's bouncing off the 10,000 rpm redline constantly.

[stoneam2006]

The motors are rated at the prop,2 or 4 stroke. A 2 stroke will rev quicker but does not have the same torque/power as a 4 stroke. It does weigh a bit more but not enough to make so big a

difference that you need to go from a 90 two stroke to a 100 four stroke to get the same top end. The biggest thing is to get the correct prop so the engine peaks out a couple hundred rpm under the rated number with a full load on the boat. Or empty hits the redline. I would go 4 stroke all day long if I was buying a new outboard. Your minimum hp should be 65% of the max rated hp of the hull. I didn't do the math on yours but I would spend the extra 900.00 and go for the 115,you will be happier in the long run. As far as rebuilding a 2 vs 4 stroke if you follow mfg scheduled oil changes you will probably never have to rebuild that 4 banger. That would be the least of my worries. BTW raced MX for 15 years and 2 strokes needed rings/pistons every 15-40 hours of riding time depending on if it was a 125 or 250. The Yamaha 4 strokes would go for 2 - 3 seasons without anything but oil changes and that's bouncing off the 10,000 rpm redline constantly.

Agree but if it does go the cost is 3x or better to fix

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[Bozeman Bob]

Its not any more likely to blow than any inboard/marine/IO/car engine that's out there right now. There not turning 10,000 rpms like a race bike engine,they lope along at 4-5 grand and are pretty much bullet proof. As long as were at "it", a two stroke as noted has half the cycles as a 4 stroke so in theory will wear out twice as fast as a 4 stroke.

[Prof T]

 I presently run on a1984 90hp and troll on a 1986 9.9. Looked at new Mercs and REALLY like the idea of troll control on the big 4 stroke. I think my boat setup works for it, and I'd keep the old kicker for backup/emergency.

 

I use my boat a lot. Fish 4 times a week at least. I can't imagine how many hours I have on the kicker. Floor's been replaced. Canvas is in good shape. Pumps are all good. Livewell's big. Aluminum doesn't leak or rot. Transom's solid. Biggest shortcoming is that it has only got a 7 ft beam.

 

For me putting a 13 K outboard on it is a life commitment. Finding a used  late model 18 + with 8 ft beam and suitable engine options has proven cost prohibitive. Going to hold off for the rest of the season to see if a better option comes up.

 

Feel free to PM me if you've got one and are thinking of making a move also.

[BAZOOKAJOE]

I'd run the one you have till it dies. Then you could always have it rebuilt. Putting a new $13,000 motor on an old boat doesn't make sense.

[mr.mo 55]

My son just put a new 115 Yamaha on his 19 ft. sea nymph runs great trolls great real quiet . trolls around 1.9 so far 39 mph. top end but still breaking it in. it is a 4 stroke. we like it.

[rolmops]

 I presently run on a1984 90hp and troll on a 1986 9.9. Looked at new Mercs and REALLY like the idea of troll control on the big 4 stroke. I think my boat setup works for it, and I'd keep the old kicker for backup/emergency.

 

I use my boat a lot. Fish 4 times a week at least. I can't imagine how many hours I have on the kicker. Floor's been replaced. Canvas is in good shape. Pumps are all good. Livewell's big. Aluminum doesn't leak or rot. Transom's solid. Biggest shortcoming is that it has only got a 7 ft beam.

 

For me putting a 13 K outboard on it is a life commitment. Finding a used  late model 18 + with 8 ft beam and suitable engine options has proven cost prohibitive. Going to hold off for the rest of the season to see if a better option comes up.

 

Feel free to PM me if you've got one and are thinking of making a move also.

you might want to look for a  19 or 22 starcraft islander or a Sylvan Offshore ( exact same boat out of the same factory but with a different name) There are outboard driven ones of the size that you want and they are aluminum and cost anywhere between 3 and 5  thousand.

Edited September 24, 2016 by rolmops

[jimski2]

My old 18 foot Lund had a 115 Evinrude replaced with a 115 Honda. The narrow beam caused the transom well to sit underwater and the bilge pump ran forever. Be damn careful putting all that weight on the end of your boat. I would recommend the weight being the primary decision maker. The new 4 strokes made boat designers come up with wider beams to hold the heavier engines. Going 25 mph is adequate to get you out for fishing.

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[mr 580]

Another thought for you- if you troll a lot update your kicker to a four stroke. They pop up used fairly regularly especially towards spring. No smell, little maintenance and they are good on fuel. Then when you find a boat package in your budget you'll have already updated the kicker. IMO in a mid range motor like a 90 or 115, the four stroke is the way to go. I don't see a 13K investment as a wise choice into a 30 year old boat however. Best to be patient and keep looking. Would think you could move up 20 years for 15K in a low hour boat, motor and trailer.

[Sk8man]

As far as kickers go I recently bought a long shaft 9.8 4 stroke to replace my 1987 9.9 2 stroke long shaft. I was able to steer my boat with the 2 stroke long shaft without a steering connector although I had the EZ steer set up on it originally. I found that I could steer the boat in most conditions with the big motor (135 outboard) without it. The exception was in real windy conditions (e.g. white cap stuff) which I had to use the big motor most of the time. The new 4 stroke is able to run it into even stiff wind without having to crank up the big one. It seems to have more torque at the prop I believe as everything else is  virtually the same (e.g. 20 inch shaft, similar 3 blade prop, 91 lbs vs. 87 on the 2 stroke). I don't think it pushes the boat as fast top end though but that is important only in an emergency situation and the gas economy is more important there with a separate 3 gal. tank. It works sweet.

Edited September 26, 2016 by Sk8man

[Xxx]

The most important factor I've read so far is be patient, your ship will come in. I could of kicked myself in the arsh many many times, as deals came up on here that were almost to good to be real!! Like what I paid for my boat plain Jane I could of bought 5-10 years newer all set to go fishing. Nearly makes me sick!! You do very well with what you have!! Piece it together over a period of time, as your deals come along and you'll be ahead by the thousands of $$$$

[jimski2]

I have a 1991 90 hp Evinrude that I change spark plugs a couple times a year as the 25 year old motor is getting tired but can still travel 30 mph when I try to blow the carbon out. My 9.8

Honda 4 stroke with remote control and power trim and tilt is my trolling and emergency get home engine, connected with a Panther front connect steering arm it is easy to hook up when changing engines. The transom weight is fine as I removed the starboard battery Tyron the boat. The Honda charges my battery when it is in service as it also has electric start. The cost of the Honda was $3800 and it serves me well as now after fishing all year the six gallon tank of gas has a gallon of gas in it. The single battery has ignition noise on the fish finder at higher speeds but fine at low speed.

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[jimski2]

I have a 1991 90 hp Evinrude that I change spark plugs a couple times a year as the 25 year old motor is getting tired but can still travel 30 mph when I try to blow the carbon out. My 9.8

Honda 4 stroke with remote control and power trim and tilt is my trolling and emergency get home engine, connected with a Panther front connect steering arm it is easy to hook up when changing engines. The transom weight is fine as I removed the starboard battery Tyron the boat. The Honda charges my battery when it is in service as it also has electric start. The cost of the Honda was $3800 and it serves me well as now after fishing all year the six gallon tank of gas has a gallon of gas in it. The single battery has ignition noise on the fish finder at higher speeds but fine at low speed.

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[MCF]

I have a 1986 Sea Nymph 19 which I bought a couple years ago.  Previous owner did the floor, I did the transom, new high top, new steering cable etc.  Bought a used 90 hp Mercury 4-stroke.

Boat does not leak a drop.  Given all that, when you look at new it is 35 grand plus.  And yes the deal pops up from time to time in the mid teens to do an upgrade.  But the question I have is why upgrade when

I know what has been done to my boat, just like the gentleman who started the post.   

[Captain Carl Bish]

Don't hesitate, go get your new 4 stroke.  You will save fuel, you will get a warranty up to 6 years.  I just pulled the trigger on a pair of 2016  150 hp mercs, sweetest boat motor I've every seen!  

 

Suzuki

Yamaha 

Honda 

 

All are all great as well....I went with merc because their 90-150 engines are over built, light and made right here in the USA...I mean they are made from blocks FORGED in Wisconsin!  I was entertaining other engines until I heard that!!

 

Good luck, I think you would be fine with the 90....but the 115 is very sweet.

[Prof T]

Finally did it and will offer my initial reactions. Replaced mid 80’s90 Evinrude 2 stroke with 90 Merc Command Thrust on a 19.5 ft Sea Nymph w/ 7 ft beam. Engine weighs about 375 lbs wet vs 300 for the old motor. Boat doesn’t squat too much while at rest w/ splash well drain holes easily 2†above water line. (I still have my 9.9 kicker on w/ a 6 gal. fuel can also).

 

Although still breaking in, it appears top end will be about 37 mph…more than I need and a little quicker than the old gal. Hole shot seems respectable as well. Have not run with a full load of people yet.

 

Command Thrust: Puts a lower unit from 150 on the 90. Give you a bigger rudder for trolling stability, about a 10% lower gear ratio and the ability to swing a larger diameter prop.

 

Troll Control: Engine’s natural idle is at 700 rpm. Troll control give you digital control through the smartcraft tachometer gauge of engine rpm from 550 to 1000 in 10 rpm increments.

 

Fished the other night. Started in a rather slack area, slight current and a mild head wind. Set rpms to 570 – 590 to maintain 1.1 to 1.3 mph SOG. Seems as though I will able to keep my speeds low enough for walleye troll, definitely better than I could do without the troll control.

 

Moved to higher current area which is more commonly where I fish here on the SLR. Needed about 750 – 780 to maintain. Very easy adjustment. Once set watch gps speed, add or subtract rpms by 10’s to achieve desired speed.

 

Fish on. Shifter to neutral. Land fish. Shifter back in gear. Turn troll control back on. RETURNS TO PREVIOUS SPEED SETTING. So far, one limit of walleyes, no lures lost and a motor that operates as advertised.

 

Two issues to be addressed though. First, the motor came through without a steering trim tab under the cavitation plate, just a flat anode. Definitely pulls hard unless perfectly trimmed. Dealer is getting one.

 

Second one not as easily corrected. Troll control is operated through push buttons on Smartcraft Tachometer. Be sure it gets installed where it is easily accessible. Mine ended up on the right side of the steering wheel. Although it’s big, getting at it unless seated at the helm is a pain.

 

Disclaimer: I’m not trying to promote a brand of motor or dealer…I just did a lot of research and found a system that I think fits my way of fishing. Hope I answered someone else’s questions.

 

 

[Bozeman Bob]

Sounds great. The way it trolls down it sounds like you could sell your kicker to recoup some of your money and shave some weight off the stern at the same time. If your concerned about the safety factor of getting back in case of engine issues, [hitting a log or something like that, not mechanical ] maybe get a smaller kicker with a self contained fuel tank that weighs less than your present unit.

[lrg355]

I put a Yamaha F70LA on my Sea Nymph GLS 175 about two years ago. It weighs 257 lbs. Is the lightest engine in that range, 2 or 4 stroke. Running gauges from my Lowrance HDS touch. Boat previously had a 115 Johnson. It was a rocket but just got tired of the smoke, hard starting and fuel consumption. The Yammy runs all day on fumes. Fuel consumption according to the Lowrance is 9-10 mpg at best cruise about 4000 rpm. Probably get a about 20 mpg trolling. Also hooked into the troll control with a switch. Can go up or down in 50 rpm increments from 600 to

0 1200 rpm. No more carburetors for me. EFI all the way. Touch the key and it runs.

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[Mercury13]

I have a 2000 90hp Mercury 4 stroke on an old 18 Starcraft Holiday. It will troll down to 1.5 mph and uses far less than my old 15hp Johnson kicker. I have a 12 gallon fuel tank but only use a 6 gallon tank that came with it. In the years I have had it I have never came close to running out in a day.

[meangreencj7]

I have a 2015 115 Yamaha and a 2015 9.8 Tohatsu on my boat, this spring I ran the Yamaha for about 4-5 hours at about 20-25 mph and the Tohatsu for about 40 hrs at 2.5 mph and only went thought about 15-16 gallons of gas. only 3/4 of a tank.

 

Last year with my 1996 90 hp 2 stroke mercury and my 1998 9.9 Johnson i did about the same amount of time and i went through about 30-35 gallons of fuel.

 

I can accually talk to my passangers while going full speed with the Yamaha, had to use gestures and scream with the mercury.  and no choking on the fumes from the Johnson when going with the wind.

 

I am much happier with my 4 strokes.