I just got a great deal on a used 90hp johnson weighing in at about 330 lbs. I put two half inch bolts in the topmost holes (one on each side) and through the transom with a steel plate on the inside of the transom well. (the aluminum plates at lowes were too flexible at the same thickness so I went with steel, I painted them with rustoleum and they should be better than aluminum)
Do I really have to put the other two bolts in the bottom and drill the nightmarish hole right through into my rear berth right near the water line? I just imagine waking up to wet feet. My plan is to make sure the engine works well enough on the boat to want to keep it and then if I notice any weird kind of motion or shaking of the motor then put the other bolts on as a last resort.
Shouldn't the two bolts be sufficeint, they are steel 1/2 inch bolts from trusty west marine? If I go slow on turns there shouldn't be large shearing forces at the bottom half.
two bolts or four?
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Billy
- First Officer
- Posts: 439
- Joined: Tue Jan 06, 2004 3:50 pm
- Location: Dunn NC 2001-26X140 "XX"(DoubleCross)
I would say "definately Yes". When you hit reverse there is nothing to keep the torque from lifting the engine out of the water and cracking/breaking the top of the well. Drill the holes and fill with silicone (in case you decide to remove later). It shouldn't leak; besides, you can always fill it later. Use a plate across the 2 lower bolts inside.
Just my $.02.
Just my $.02.
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Sloop John B
- Captain
- Posts: 871
- Joined: Sat Jan 03, 2004 2:45 am
- Sailboat: MacGregor 26X
- Location: Florida 'Big Bend'. 02x Yamaha T50
Most of us have four bolts going into the motor well.
Make sure your motor isn't down too far. Cavitation plate should be level with bottom of transom.
Get some advise from marina installers on drilling and sealing lower transom. I gooped the gazoo out of mine with 5200, and then learned it is pretty much permanent.
Make sure your motor isn't down too far. Cavitation plate should be level with bottom of transom.
Get some advise from marina installers on drilling and sealing lower transom. I gooped the gazoo out of mine with 5200, and then learned it is pretty much permanent.
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Don T
- Admiral
- Posts: 1084
- Joined: Fri Jan 02, 2004 7:13 pm
- Sailboat: MacGregor 26X
- Location: 95 2600 "SS OTTER" - Portland OR - Tohatsu 50 - Hull#64 (May 95)
Hello:
Yes, install the lower bolts. Use a good sealer like polysulfide or 4200 if you think you might remove them later. Don't use RTV, it just won't seal properly and the silicone will be hard to get off later when you want something more substantial to stick.
The problem with reinforcements on the inside is being too rigid. You need something strong yet flexible that does not present hard pressure points where stress cracking can occur. Search the archives. An owner had problems with transom cracks.
Yes, install the lower bolts. Use a good sealer like polysulfide or 4200 if you think you might remove them later. Don't use RTV, it just won't seal properly and the silicone will be hard to get off later when you want something more substantial to stick.
The problem with reinforcements on the inside is being too rigid. You need something strong yet flexible that does not present hard pressure points where stress cracking can occur. Search the archives. An owner had problems with transom cracks.
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Frank C
I honestly feel that transom reinforcement can be less, but better. As I explained to both Billy and Mark, my Mac dealer discussed it with Roger in 1999 before reinforcing my transom for the Suzuki 60/70. Granting that it's less than half of Billy's thrust, I continue to believe that my dealer did it right. (Remember too ... Gene Arena and his brother were among the earliest builders of hydroplane racing boats, late fifties to sixties).
Sorry that pix are now lost. But this description is easy ... the upper bolts are only reinforced with a solid aluminum wedge plate on the exterior transom, under the motor saddle. That plate is one-inch thick at top, maybe half that at bottom. Couldn't hurt to have a motor-well plate, but there's nothing at all inside my motor well except two washers and bolts.
Most importantly, inside the lower transom the lower motor bolts pierce an aluminum channel "C" beam, flat to transom, channel facing bow-forward, spanning the four factory knees. This beam is sized about 1.5" by 2.5" (like a 2x3 stud) by quarter-inch-thick aluminum.
This long beam extends across most of the inside-transom, picking-up the lower motor mount bolts and also the bolts that mount the rudder brackets. The actual beam length is about 3 inches beyond the span of the rudders, but its "working span" is the factory knees, rudder-to-rudder. Obviously then, thrust is spread across this entire transom span, and the transom is "tied-together" across that entire span, and that length of beam can also provide some slight transom flex.
This transom took a lot of time and effort. They had to align the beam to match all 6 rudder bolts, the 2 motor bolts, and then drill it precisely for bolts plus the transom thru-hull drain. I think the effort & time were worth the price ($750 to $900?) ... I wouldn't hesitate to mount Billy's Suzi-140 onto my transom, as is.
Sorry that pix are now lost. But this description is easy ... the upper bolts are only reinforced with a solid aluminum wedge plate on the exterior transom, under the motor saddle. That plate is one-inch thick at top, maybe half that at bottom. Couldn't hurt to have a motor-well plate, but there's nothing at all inside my motor well except two washers and bolts.
Most importantly, inside the lower transom the lower motor bolts pierce an aluminum channel "C" beam, flat to transom, channel facing bow-forward, spanning the four factory knees. This beam is sized about 1.5" by 2.5" (like a 2x3 stud) by quarter-inch-thick aluminum.
This long beam extends across most of the inside-transom, picking-up the lower motor mount bolts and also the bolts that mount the rudder brackets. The actual beam length is about 3 inches beyond the span of the rudders, but its "working span" is the factory knees, rudder-to-rudder. Obviously then, thrust is spread across this entire transom span, and the transom is "tied-together" across that entire span, and that length of beam can also provide some slight transom flex.
This transom took a lot of time and effort. They had to align the beam to match all 6 rudder bolts, the 2 motor bolts, and then drill it precisely for bolts plus the transom thru-hull drain. I think the effort & time were worth the price ($750 to $900?) ... I wouldn't hesitate to mount Billy's Suzi-140 onto my transom, as is.
Last edited by Frank C on Thu Aug 11, 2005 2:38 pm, edited 1 time in total.
My original 210 pound tohatsu tldi 50 was installed by my Marina del rey dealer Mike Inmon's regular installer Andersson(A-hole is more like it) marine with only the 2 upper bolts. Never had a problem, but when I moved up to the 315 pound tldi 90 my new motor dealer/installer recommended all 4 bolts, plus inside boat and outside boat/well reinforcing plates, which is what we did. Never had a problem.
Rolf
Rolf
