Seafari 20 Power

[NorthBay]

Hey Folks,

I am new to the site having just bought a 78 Seafari. She needs a lot of cosmetics but is solid as a rock! The boat came with an 1985 Evinrude 150 and my intention has been to run it till I can put away some cash for an upgrade. No idea of the hours on it but it looks pretty clean. However, I checked compression and got a bit of a dissapointment. Port - 100, 95, 95 Starboard 80, 85, 80. Carbs need rebuilt. Trim/tilt is bad too. It sat for 3 years. I have a yamaha 115 four stroke at my work I could buy fairly cheap but it needs some work...lower unit and maybe few minor things as well. I have had tilt/trim trouble with it over the years too. Yamaha has 1400 hard hours of summer camp skiing and tubing. Where would you guys put the money and effort? Is the yamaha a good match for the boat? Your thoughts are appreciated!

[Bushwacker]

Welcome aboard! The Seafari is probably the most versatile of all the 20' models and a 78' would have many nice upgrades not found in earlier models!

Regarding power, it sort of depends on how you plan to use the boat and what you want out of it, i.e., water skiing at high speed in flat water, cruising with a heavy load, good economy with maximum range, frequent offshore use in rough seas, etc. I ran mine for over 30 years with a 1975 300 lb V-4 2-stroke that was about 100 hp at the prop and averaged 2.8 mpg on 6 long trips to the Abaco's in the eastern Bahamas carrying very heavy loads. It wasn't fast, cruising at about 20 kts @ 4500 rpm, but it rode extremely well in rough seas because it was well balanced with that light motor on the transom. The 20' hull will start going airborne at 20 kts in seas over about 3', so you can't use a lot of power if you run in those conditions. The VDH hull design is very efficient compared to modern hulls so it doesn't need as much power, but it is weight sensitive and performs best with lighter motors.

For the near term, if you can get the 150 running, I'd suggest doing a decarb on it, as it may just have some stuck rings. Then recheck the compression when warm or ideally do a leak down test on it. Those motors are simple and easy to work on, although that trim & tilt assy can be a bear on either motor if you have to take it apart! An '85 is probably the 90 degree crossflow design instead of the newer 60 degree looper, so it'll be a 2 mpg rig! It's probably about the same weight as the 115 4-stroke. The latter should give you close to 5 mpg, but you'll have to change the controls and probably most of the gauges, and would be expensive if you had to have a dealer do much work on it. It will be adequate power if propped correctly, provided you don't want to cruise faster than 20-25 kts. I'd probably lean toward that motor if wt. and cost are similar to fixing the V-6.

The best older power for that hull IMHO from a balance/ride perspective would be a light V-4 2-stroke, either a 115-120 OMC/BRP looper or a Yamaha 115-130, so if you can get that V-6 running, it might be worth shopping around for a newer used motor. For modern clean motors, I like the E-TEC, either 90 I-3, 115 V-4 or 135/150/175 V-6. For 4-strokes, I wouldn't pick anything heavier than the 140 Zuke, which is about the same weight as the V-6 E-TEC.

[NorthBay]

Thanks for the reply bushwacker. The boat will primarily be used for fishing the Chesapeake and Delaware Bays but I would love to drag it down to the outer banks for a week in the summer and try to get offshore. The 150 rude weighs 380 and the yamaha 420. The boat is missing all guages so that won't be a factor. I am leaning toward fixing up the old evinrude. I could rebuild it for the cost of the work on the yamaha. I guess the choice then is a rebuilt thirsty old two stroke or a somewhat tired out 4 stroke if I stick with one of my current options. The evinrude sure is easier to work on and whatever I do it will be me doing the work. Thanks again.

[cdavisdb]

You should get better than 2 mpg with the 150. I had a 20 seafari with a 150 black max of about 1978 vintage. We loaded the boat very heavy(3 divers, 9-10 tanks, 100-150 lb ice) most of the time. I don't remember exactly what my fuel consumption was, but for sure it was a little better than 2 even when loaded heavy. 45 gallons was enough(barely) to run 40 miles offshore and back, plus idle around for 6 hours or so. When it was light, fuel consumption went way down,

[Bushwacker]

Either of those bays can build up a short steep chop, so I would think ride (and lighter motor) would be a top priority. The boat will be better balanced with the lighter V-6, and you're right, they are much cheaper to rebuild than a 4-stroke. The exhaust valves are the weak link on the 4-strokes, so I wouldn't buy one without doing a leak down test.

Since none of those compression numbers are real low, I'd bet there is a good chance you just have some stuck rings, esp on the stbd bank. Those motors were prone to carbon build up anyway, so I'd definitely try doing a decarb on it, as that's all it may need. It's also very easy to pull the heads to check for scored cylinders. If it needs a rebuild however, I'd start pricing some newer used 2-strokes before diving into it!

[FishStretcher]

I think the F115 is a nice outboard. I have about 420 lb on the transom. But that's combined weight of the F100 and a kicker. I don't care for two strokes, and yamahas seem to last, but even I would suggest decarbonizing first. And a stern lifting prop.

[Bushwacker]

Originally Posted by cdavisdb

You should get better than 2 mpg with the 150. I had a 20 seafari with a 150 black max of about 1978 vintage. . .

I agree that any of the smaller V-6 Mercs will burn less gas than the old cross-flow OMC's, so would be a good choice if you can manage corrosion issues. I bought my V-4 in 1975 because there were lots of 20 year old Johnrudes running around then but I never saw any Mercs more than about 5 years old.

[GameOnSalmon]

Northbay,
Don't know if you got this up and running yet with the cold snap going on. Denny hit the nail on the head. That 150 is Notorious for carbon build up.

If the motor has not been De-Carbed and has been sitting for awhile its time to knock it out. I would suggest a couple of things to really help that.

First off Use Seafoam and do a Super deep De-Carb. I actually take the Airbox cover off and fire up the engine on the hose and shoot Seafoam straight into the carbs several times. Then Load it up good and kill the motor. Let it sit for about 15 mins. Fire it up on fresh fuel from an auxillery tank and run it for a few.

I will do this 2 to 3 times. Once you have done that.

Pull all 6 spark plugs and check your compression then? If you have good even compression I would then suggest Rebuilding the carbs before you run it out much. Just my 2 cents and no change required.

Good Luck.. One of my Favorite Engines you have there.

Robert

[NorthBay]

Thanks for the reply Robert. The decarb did not solve it unfortunately. Actually, after retest of compression, I can't get numbers as high as the originals. I decided to go with the yamaha f115. It passed a leak down test and is running well. picked up a lower unit and tested it yesterday. It is mounted on a novurania 18' RIB that is in pretty poor shape and I am getting the seastar steering and controls/instruments as well. I am basically going to strip the Novurania down and get rid of it. I have a lot of work to do to the seafari before the motor goes on...mostly cleaning, painting and rigging. Looking forward to it!

[FishStretcher]

I think a Solas Amita 4 blade stern lifting prop, 13 x 15" pitch would be a good prop for that engine. I use one on a F100 which has a bit more reduction in the gearcase, so I think it would be great for the F115 with a 2.15:1 ratio versus the 2.31:1 reduction in the F100. They should be about $100 for the aluminum one. Boats.net carries them, but they aren't my favorite online retailer.