New here also - Page 2

tommy54 · #1 07-07-2017, 01:18 PM

Thought I'd revive this thread. The rebuilt Johnson Oceanrunner has a lean sneeze that can't seem to be cured. I had hoped that the old motor would give me a year or two of service, I've had pretty good luck with 2 strokes on our chase boats. I think I'm going to take the leap and buy a new motor for it. We don't need to run fast, our lake is only 7 miles long. I'll be taking it down to Pine Island at some point this winter, but I won't be in a hurry then either. I like the 369lb weight of the Mercury 115 4 stroke. Some say you need a lot more horspower, but I'm happy with the power right now, and I want to keep the boat light. I'd want to go with a 25" shaft, so she may go under the knife to raise the transom. I had hoped to wait for the off season to do that, but this engine is stumping every mechanic around.

tommy54 · #2 08-10-2017, 10:43 PM

I decided to sell the 115 Johnson and mount a Yamaha 90 fourstroke EFI that I pulled off one of my rental pontoons. I know it will be bit underpowered, but I'll prop it so it works. Problem is, the wood around the engine mounting bolts is wet and a bit soft. I could trim the old motor up, stand on the cavitation plate and jump up and down without any flex in the transom. Can I mount the Yamaha and run it for the rest of the year? I'd prefer to tear it down and do it right, but I don't have the time right now and I really should have a chase boat. Any opinions are welcomed...

billythekid · #3 08-11-2017, 08:14 AM

it will be fine, if you can bounce on it and its not flexing you are fine, at this point its safe to say any of the seacrafts from the 70s have or had a rotten transom, the fiberglass front and back is alot stronger than you think.

Terry England · #4 08-11-2017, 09:01 AM

Quote:

Originally Posted by billythekid

it will be fine, if you can bounce on it and its not flexing you are fine, at this point its safe to say any of the seacrafts from the 70s have or had a rotten transom, the fiberglass front and back is alot stronger than you think.

x 2

FLexpat · #5 08-11-2017, 09:05 AM

X3
If it bugs you then put some 1/4" aluminum plate on the inside and outside of the transom and use the motor mount bolts to sandwich it. You can run it for a really long time like that.

Capt Terry · #6 08-11-2017, 03:16 PM

Quote:

Originally Posted by FLexpat

X3
If it bugs you then put some 1/4" aluminum plate on the inside and outside of the transom and use the motor mount bolts to sandwich it. You can run it for a really long time like that.

Another Moesly approach suggested to me by Skippertee was I added aluminum angle iron to the engne bottom holes on the inside of the transom. This was .25 thick x 2" x 2" and about two foot long (fits between the stringers). The "L" shape provides a lot more moment of inertia (stiffness) than a single flat plate. A double flat plate would be quite stiff as well, but requires removing the engine. My top holes were in better shape.

McGillicuddy · #7 08-11-2017, 11:49 AM

You'll be fine. 90 ponies is fine, even in gray. You'll want a stern lifting prop, something described as "easy to turn," meaning little cup, mild rake progression and fairly large blade area with a fairly straight front edge and nicely curved rear. that sounds kinda, well... anyway a semi-cleaver, probably 13-3/4 x 14 or 15 pitch. Make sure you are able to dial it up to max recommended rpm full of gas and peeps and ginger ale. I always suggest the quicksilver black diamond as the starting point. cheap, kick ass prop perfect for a 33 mph 20' seacraft with 90-115 hp. Yamaha's own semi cleaver is also a decent starting choice. a 4 blade with maybe a little less diameter will also fit the call. You'll want the anti-cav plate about 1-1/2" above the keel with the plate parallel to keel.

cdavisdb · #8 08-11-2017, 07:22 PM

A belated welcome to CSC!

Charlotte Harbor is my favorite Florida cruising ground. If you get back down here, let me know. I can put you and your kids on some fun stuff.

Connnor

tommy54 · #9 08-14-2017, 10:54 PM

Thanks for the input. That got me thinking about what material I may have laying around. I had a transom reinforcement plate from a pontoon(1/2" aluminum) that I cut in half, put the top half in the splashwell, and the bottom half down in the bilge for the lower two bolts. It may not be a permanent fix, but it's a lot stronger than before. I took the opportunity with the old engine off to pressure wash the bilge, then got sidetracked with removing old wiring in the bilge. I am moving the battery up to the console as long as I'm cleaning things up for better weight distribution. I do get concerned with the 20" transom. Someone added a layer of plywood to the floor, and there are no more scuppers, so this is not a self bailing boat.
Thanks for the info on propping. I believe I have a 15 pitch Yamaha prop on there, so it may just work. I'm anxious to see how the 90 horsepower motor performs on the boat. I've always rigged engines with the cavitation plate level with the bottom of the hull, is it a Seacraft specific thing to put it 1.5" above the bottom of the keel?

McGillicuddy · #10 08-15-2017, 12:45 AM

Quote:

Originally Posted by tommy54

Thanks for the input. That got me thinking about what material I may have laying around. I had a transom reinforcement plate from a pontoon(1/2" aluminum) that I cut in half, put the top half in the splashwell, and the bottom half down in the bilge for the lower two bolts. It may not be a permanent fix, but it's a lot stronger than before. I took the opportunity with the old engine off to pressure wash the bilge, then got sidetracked with removing old wiring in the bilge. I am moving the battery up to the console as long as I'm cleaning things up for better weight distribution. I do get concerned with the 20" transom. Someone added a layer of plywood to the floor, and there are no more scuppers, so this is not a self bailing boat.
Thanks for the info on propping. I believe I have a 15 pitch Yamaha prop on there, so it may just work. I'm anxious to see how the 90 horsepower motor performs on the boat. I've always rigged engines with the cavitation plate level with the bottom of the hull, is it a Seacraft specific thing to put it 1.5" above the bottom of the keel?

Pretty standard on the 20 hull. more bang for your prop. not sure if your yammie is 400 lbs or newer light one, but I think up an 1+" will help.

Regarding the scuppers - did they glass over the scupper holes in the bottom of the hull?