Power for a restored 18SF

[pjzabo]

I just purchased a 1974 18' Sea Craft from a friend. It has a freshly restored transom and new gas tank. Boat is in nice shape but doesn't have power. So I am looking for a used four stroke outboard. What does everyone recommend? I see a lot of people talking about 150HP on the Potter 18s. Would 90-115HP be enough, or will I be wanting more power? I fish on the Long Island Sound and do mostly shorter hops - usually not more than 10-15 miles from my home port of Stamford. I was thinking of trying to find a low hours 2-3 year old 115HP Suzuki or Yamaha. Thoughts?

Thanks, Pete

[76Red18]

I would be more concerned about weight than hp. Try to stay under 400 lbs; hard to do with any 4 stroke.

[KOS]

I am also concerned about the weight/ power issue. I own a 1978 18' with a raised 25" transom. Prior to raising the transom I had a 115 hp Johnson 2 stroke that pushed it fine for me.

I'm considering repowering with either an etec 90 hp (335 lbs) or suzuki 90 (348 lbs). My ideal choice would be the Yamaha F115 (412 lbs) or etec 115(390 lbs)but when you add the weight of the oil and prop both are about the same weight and above the 400 lbs mark.

Love the boat but with the new technology, I am not sure which direction to go. I've also moved the console up 5 inches and moved the batteries forward as well. I'd like to avoid moving the gas tank if possible. Any suggestions?

Thanks

[asdfhood]

My 18 SF is a 1987 with a 25" transom. Powered by a Yamaha 2 stroke 130, about 360 lbs. I would be concerned with any repower that exceeded 400 lbs also. I have been salivating over a Mercury 125 optimax, wt about 375 lbs. This is a new motor for 2010 and as of now I know more about it than my dealer, just from the merc website. The boss says I can't have one yet. Maybe i'll have to devise a "plan" even though the Yamaha is just fine.

[pjzabo]

Everyone - thanks for the feedback. I'm pretty sold on going four stroke. I appreciate the advice on the weight factor. I will focus on staying below 400lbs. I liked the Suzuki 140 because it had the best power-weight in the 100-150 HP range, but it is listed as 421 pounds with a 25 inch shaft. That new Optimax 125 sounds perfect, but I am hoping to find something 3-4years old at a lower price with all the controls. Guess I may need to focus on a 90HP motor. Does 90 HP push this boat nicely?

[Bigshrimpin]

I haven't run it yet, but I have a 2002 Suzuki 90hp in my garage that is going on my 18sf.

[McGillicuddy]

Father Frank has a 90hp optimax on his 20' Seafari. If remember right, he gets 34 mph top end, and right about 5 mpg at a 24-25mph cruise.

I think an etec 90 - 40 pounds lighter, would be a great match for the 18.

[pjzabo]

Anybody have real world performance numbers on the 18 with various motors? That 90 ETEC seems a nice match. I would really like to be able to cruise efficiently at 30mph when seas are calm, and wouldn't mind a top end in the 40mph range.

[bmajvi]

I think it all depends on where and how you intend to use your boat, and what's really important to you. Hole shot, top end, economy, how much weight/how many people you expect to carry, chances of getting stuck in snotty conditions, etc. all help point the way. I was in the same position as you (new-to-me nice '74 18 SF w/o power) in 2002, and I went with a spankin' new Suzuki DF140. A lot of people said/say it's too much weight, and I agree that it's at the high end on weight, but I ran it for five years with zero problems, great performance, and remarkable economy.

Top end of 42 mph (GPS) on flat water w/2 people and around 40 gallons of gas, bimini folded down, and a decent hole shot. Might have propped a little different to get a little higher top end, but I liked the hole shot & mid-range performance, and most of the time I wouldn't run much over 30 anyway. The "extra" power was a real comfort in crappy weather though, she never struggled to get on plane, even with a lot of weight/into the wind & seas. A full day of mixed use (WOT, fast cruise, trolling, wake-boarding, putt-putting through no wake zones, etc.) with 2-4 aboard always yielded right around 5 mpg overall for the day.

I put the batteries under the console and kept as much junk forward as possible, and the only time I had any issues was backing down in seas - always a good idea to have & use spashboards once the engine is tilted down! Good luck!

[Bushwacker]

Good summary, and great idea on the splashboards . . . all the benefits of a bracket without the expense!! The 20' hull will plane at about 12 mph and ride great with a 300lb motor because that's what Moesly designed it for! You can prop a small motor for a good hole shot and good load carrying ability like Fr. Frank has done, but you'll give up some speed. As you go heavier, you'll burn more fuel, increase min planing speed and tend to hurt the ride because of aft cg shift, so I'm a little biased towards lighter motors. These boats have a lot less beam than the new boats you see with 4-stroke motors, and that's one reason these old classics ride so much better!

The heaviest 4 stroke I'd consider is the 140 Zuke and it was my second choice. I went with the 150 E-Tec (actually 165 hp at prop) because it's about same weight, is even quieter at cruise (less rpm), has about 25% more displacement and MUCH more mid-range torque, and also gets great mpg. The E-Tecs run very lean below 2000 rpm; at hull speed (4.5-5 mph)/800-900 rpm the I-Command gage (with gps spedo/engine computer fuel flow) says I'm burning about 0.5 gph and getting about 10 mpg, which is better than the Optimax and any 4 stroke! Can be significant if you do much trolling, and it can provide a lot of extra range! If you ever run low on gas, you can go a LONG way at hull speed on not much gas!

At cruise with a very heavy load and big bimini top up with my 15x15 4B power/holeshot prop (which pops boat up on plane instantly at less than 50% throttle), I get about 4 mpg at 3700/3800 and 25-27 mph, with about 40 mph max. With a light load/full fuel and my 14.125x20 4B speed prop, I cruise at about 3200-3300/25-27 mph and about 5 mpg. Top speed is almost 50 if I put the top down. All this is with a very rough bottom (3 coats of bottom paint, except about 30 spots where it's peeled off down to gel coat!); currently working to fix that problem. I've kept a log of all fuel burned/miles run since repower and average mpg for about 230 hrs is over 5 mpg, due to effect of zilch fuel burn at low speed. With zero problems and only about 3 gal of oil burned in 3 years, I'm pretty happy with the E-Tec. I originally considered a 115 since I ran a 1975 V-4 90 hp-at-prop "115" for over 30 years and was very happy with it's performance. A 115 E-Tec would have burned even less fuel, but I've ended up running heavier loads than than I expected, like 4 divers with full gear and tanks, so it's nice to have the extra margin in those situations.