Re Power
 

I have an SF 18 with a 1998 Yamaha C115 that I'm thinking about re powering come spring. The motor has been very reliable and trouble free thus far and this past summer I had it compression tested and the mechanic said it read an even 120 across all cylinders but sooner or later its inevitable that it will have to be replaced.
The Yam. C115 weighs 330 lbs. and I'm trying to stay as close to those numbers as I can for obvious reasons.
According to factory specs here are the weights of the motors I am looking at.
Yamaha.....F115....weight.....377 lbs.
Yamaha.....F90....................366 lbs.
Merc.........115EFI................359 lbs
Etech....... V4.115................390 lbs.
Etech........E90DPX (inline)....335 lbs.
Etech....... E90HGL ..............390 lbs.
Would there be a big performance difference between the Merc. 115 HP and the Evinrude 90 HP since its a two stroke compared to the Merc.four stroke ?
My mechanical knowledge and experience is very limited so any insight on the subject would be greatly appreciated.

Light is right, but I believe Merc's new 115 Command thrust is much more motor than the etec 90. I think you'll find it closer to the etec 115 in performance. It's a 2.1L with gearing that allows more considerably more prop. I'm pretty certain the etec 90 would perform similarly to your Yammie. A hair slower WOT perhaps, but excellent cruising torque curve and economy, incredible economy through manatee zones.

"bitsamonkey" had incredible numbers from the Suzuki 90 on his 18,also...
http://www.classicseacraft.com/commu...ki+performance

Thanks for bitsamonkey's link, the numbers look really good but the question brought up about staying up on plane at lower speed was not addressed and I would also like to know about that. The command thrust is slightly heaver at 363lbs. but that's still doable, if I relocate my starting battery from the transom compartment to the console it should float at an identical level its at now and she's sitting just right.

Anxious to hear more about the subject, please keep it coming.

Very happy with my merc 115ct on my 20

I can plane at about 12 knots/14 mph with a carburetted Yamaha F100- a glorified 1.6 liter F90 on a 20 foot master angler and a 4 blade prop and aquashield. Before I added the T-Top, it would come off plane at just over 10 knots. I have a 12-3/4 x 15 4 blade prop- the $100 Solas Amita 4.

http://www.classicseacraft.com/commu...07&postcount=6

It isn't the 18, but I thought the data point might be relevant.

Edit: I want the inline Etec 90 for my next outboard, if it is really 10-15 hp more power than nameplate..

Anyway of finding out and confirming the Etec 90 inline is actually 10-15hp more than its rated ? At 335lbs its the lightest in that power range.

Why not a Suzkuki do 90? 341 lbs. Super fuel efficient.

The NAEBM requires that advertised HP be within + 10% of actual HP, and BRP seems to be sandbagging on most of the E-TECs by up to the full 10%. The I-3 90 is basically 1/2 of the 2.6L V-6, which is made in 4 different HP ratings, i.e., 135, 150, 175, and 200 HP. The HP/Torque curve for the "150", which was published in a brochure a few years ago, shows it actually producing 165 hp at the prop. I suspect that the "90" is actually 95-100 HP at the prop. What's more important is the mid-range torque that you need to get on plane quickly; all 2-strokes are typically much stronger in the mid-range than comparable 4-strokes, even if they're about the same at max rpm.

I have a 19' "sawzalled" bow rider with a 2007 I-3 90 E-Tec w/ 500 hours run time. Makes 18-19 Knots at 3500 RPMs with Power-Tec 13-3/4 X 14" - 3B wheel. Tops out about 31-32 Knots. I usually run with a big load (3-4 Divers, 8 tanks, fish box gear, food cooler etc.) We ran 68 miles New Years weekend - lightest load was 5 adults - topped back off with 8 gallons.
The 90 E-Tec has a very flat torque curve and pulls like a John Deere. The 115's are a little more pipe in the mid-range - I also have two of those. I believe 3 three cylinder motors are harmonically balance and are super durable with few Hot Spots. the new G-2 Etec's are actually two three cylinder motors grafted together with a common crank - Starboard Injectors, Port Exhaust on both banks. that should tell you something.
That being said - EVERYBODY MAKES VERY GOOD MOTORS THESE DAYS. Find you best local mechanic and pick a color. It all good, Bro'!

I will consider any or all of them but there has been some comments made about the Suzuki 90's torque at mid range. On a previous post specifically on the Suzuki 90. the question of mid range torque and keeping the boat up on plane at slower speed was not addressed which leaves me suspect.
From what I have read in this thread so far, it seems the Etec. inline 90 would be a better choice over the Suzuki 90 at a comparable weight. It offers better mid range torque, and may also be under rated as to actual HP, which leaves only one question. How would the two compare in fuel efficiency ?
As I stated in my original post, my knowledge of outboards is very limited and this is going to be a substantial purchase so I just want to make sure I make the right decision and not have any regrets afterwards.

Wow, four divers, 8 tanks & equipment etc. and a heavy boat, that's very impressive for the I-3 90 Terry ! I personally would have thought you would have a hard time getting up on plane but like I said, I have very limited knowledge on the subject, hence my post asking for opinions and advice. I've only had three people once in my 18SF with fuel and fishing equipment and I noticed getting up on plane was not very swift, turning a 13.5"x 17P Power Tip Ballistic on the 98 Yam. 115.
Can you pleas elaborate on what you mean by few "Hot Spots" ?

Sounds like staying on plane at lower speeds is high on your priority list.

I think the only motors your considering that run v6 class props are the merc 115 or 90 with the ct gear case and I think the 115 etec does? Someone else could confirm.

The benefit of this us much more prop choices. I run a large prop on my motor, my boat can stay on plane down to about 14mph. It's a bracketed boat to which most will say that hurts low speed planing

Hit 45 consistently with t top. Without the top I have hit 47 in ideal conditions and wind at my back.

The "only" reason for my emphasis on staying up on plane at lower speeds is in the chop/snot.

I don't think there is another reason.

[QUOTE=sidelock;241201] . . . Can you please elaborate on what you mean by a few "Hot Spots"[QUOTE]

Before the advent of the G2 E-TEC, the exhaust ports on all V-4 & V-6 2 strokes dumped into the V between cylinder banks, creating what could be considered a "hot spot" that required extra cooling, which I suspect is what Terry was referring to. The inline engines and the G2 E-TEC do not have this problem.

Regarding fuel consumption differences between the 90 hp Zuke and E-TEC, I suspect that the Zuke will be 10-15% better at cruise, and the E-TEC will be 25-30% better at low speed (below ~1800 rpm) when it's in the stratified charge mode, so the overall average mpg will be very similar on both. For example, my 150 E-TEC burns 0.5 gph @ 1000 rpm & 5mph (=10 mpg) and gets ~3.8-4.0 mpg at cruise; my overall average when carrying a heavy cruising load (2 big coolers, groceries and gear, extra H20 and gas) is typically about 4.4 mpg. A few years ago I circumnavigated S. Florida via the Okeechobee waterway, Florida Bay and the ICW, running almost 700 miles and burning 158.5 gal of fuel and about 1.5 gal of oil for an average of 4.4 mpg. I've also made the 90 mile run up to Sebastian for CSC gatherings 3 times and I typically burn about 20 gallons each way. Another good resource if you have any questions on the E-TEC is the Owners Forum, which is supported by some very knowledgeable techs.

The other items to consider are maintenance costs and proximity to a good dealer. As Terry says, nobody makes a bad motor these days!

Very impressive numbers ! your input is very much appreciated, thanks. I was under the impression that Terry was talking about the I-3 and hot spots but I could be mistaken.

Yea, Denny knows what I'm talking about. Usually when the V-4 or V-6 2-S engines fail (OMC, Yamaha, or Suzuki) the bottom cylinder, wrist pin, Rod or crank is involved. As it is at lowest cylinder in the group and has gathered the most heat going out the stack. The 3 cylinder 2-S in-line engines (OMC, Yamaha, Suzuki and Mercury) seem to have a better disipation of heat across the block than the V design blocks that dump the exhaust in the center. I understand when they designed the G-2 they looked long and hard at what worked well and used what looks like two in-line blocks. Take a peek inside the coweling of one if you can some time. They are even weirder looking on the inside than the outside, but beauitiful castings and craftsmanship. They got a cool little sticker on them too that you don't see much anymore - it says MADE IN USA, and I'm kinda' partial to this place.

As Terry said, any of your listed motors is a very good motor.

I suspect the low speed plane should not be a problem with the zuke. 2.59 gear ratio should offer plenty of low speed guts. The fact that it can spin so much propeller should offer many prop choices, and a good stern lifter can only help your concern.

Your ballistic funky tip, by the way, is a bow lifter. Changing your prop a semi cleaver style like Yamahas own, even a 4 blade - will give you better overall performance likely lower planing speed. It will also help your hole shot with a load. 17 p with the extra cup, rake, and blade design of your ballistic might be a bit much for the Yammie on the SeaCraft hull.

The prop came with the motor when I bought the boat and I thought about replacing it but I'm playing with the idea of having the transom raised to 25" this spring and I'm undecided whether to repower or get a shaft extension kit for my existing motor. The 98 Yam 115 has been bullet proof thus far and hasn't failed me once however this past summer I noticed it running a little rough and vibrates at idle under load. I took it to Bass Pro and they pulled the carbs, cleaned them and checked the reeds but unfortunately it didn't resolve the issue. It only does it in gear at idle and low rpm. Unfortunately the nearest Yamaha technician that's on the water and can check it under load is 2.5 hours drive and I would have to leave the motor with them for a few days so I would have to make two trips.

I repowered my 1975 18' SC last summer with a Suzuki DF90 and couldn't be happier. With the factory stainless prop (14x16) it planes at about 12-13 mph, which, for me, is 3500 rpm. It tops out at around 35. I think it has more than enough mid range torque, which comes in handy running a sloppy inlet. I struggle to stuff five gallons of gas into the tank after a day of fishing. I think it's a great motor.

"I struggle to stuff five gallons of gas into the tank after a day of fishing"

I know what I would do. The more I read about the little Suzuki the more I want one.

I repowered this summer with a Yamaha 115 4 stroke @377#.
It lowered the transom about 4-5 inches from where it was with the Merc. @349#. I was surprised but the new motor was worth it.

I have since gone from 2 batteries in the back to 3 in the front of the console.
It picked it up about 3-4inches. I haven't really had a chance to run it much because the batteries were moved in December and the weather has been iffy on the coast.

The pic. is before I moved the batteries.

Oh, plus I have a 84# thrust Minn Kota mounted on the cavitation plate and it's pretty heavy.

Good luck