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Author Topic:   Small Outboard Motor Height

skred posted 01-09-2014 10:31 AM ET (US)
My 1981 Johnson 35 (remote) is mounted (not bolted) on my 1987 13 Sport in the normal fashion, but is somewhat lower than ideal (The cavitation plate is running below hull line). Without putting a jack plate or other commercially provided device on the boat, would it be unsafe to simply put a 1.5 inch block on the transom to raise the motor a bit? The standard attachment screws would still grip the transom, albeit nearer the top edge. This would give me the desired motor height. Would this plan somehow compromise the safety of the motor mounting?

Peter posted 01-09-2014 10:56 AM ET (US)
It could. You would need to bolt the motor on the transom. On the 13 Whaler, I've seen the screw clamps break loose causing the motor to jump off the transom in a sharp turn.
skred posted 01-09-2014 01:29 PM ET (US)
Did this problem occur on a motor with a spacer on the transom, or on a normally clamp-mounted motor, and did the clamp/clamps break or simply slide up and off the transom?
I use a 3/8 inch thick x 4" x 16" flat piece of aluminum mounted with 4200 adhesive on the inside of the transom, with 2 holes for the clamp "pads" to rest directly on the transom. This has (for me) been a precaution against the motor clamps sliding up and off the transom. I suppose I could bolt the motor in position, but that's a hard decision to make on a "virgin" transom....
Peter posted 01-09-2014 02:31 PM ET (US)
The incident occured on a motor directly clamped to the transom. The round "washer" at the end of the clamp broke. It was not my boat but after seeing what happened, I drilled the two holes in the transom and bolted my identical motor -- a 1977 Evinrude 35 -- to the transom.
Buckda posted 01-09-2014 02:41 PM ET (US)
If you don't wish to put holes THROUGH the transom, you could get a 1/4 inch thick strip of aluminum and screw it to the transom above where the clamps grip. That would protect from the engine clamp slipping and having the engine "going rogue" on you. Also, be sure to always use a lanyard (chain is best) on a motor that is not bolted to the transom.
Peter posted 01-09-2014 03:29 PM ET (US)
Although the motor jumped off the transom, the old pulley and wire steering system kept the motor from going to the bottom. Likewise, a modern mechanical steering system should keep the motor from going to the bottom if it were to jump off the transom. Both are effectively lanyards.
skred posted 01-09-2014 04:03 PM ET (US)
Dave, Your idea is similar to my previous solution.. I have a 3/8 inch thick plate with 2 holes cut in it for the "pads" on the motor clamps, and the plate is adhered (4200) to the transom. The clamps cannot slide in any direction inside the holes. However, if one of the clamp pads breaks, that's another story. I'm just trying to get the motor up about an inch and a half without drilling and bolting the motor to the transom.
Buckda posted 01-09-2014 05:31 PM ET (US)
It is a much lower HP application, but on my inflatable, I have a block of wood between the 6hp engine and the transom top. That transom has a metal plate for mounting, with an upper lip that keeps it from sliding around...
...but I have had a 15 HP outboard jump the transom on a 14' MirroCraft that I had as a teenager. The lanyard saved the motor because, since it was a tiller-steer and I was 15, my self-preservation instincts kicked in and I went forward when the propeller came up. The engine ingested lakewater and stalled, and I was able to re-attach the engine and row home.
On a bigger, heavier engine, I'd not rely on the steering system as a lanyard, but that's just me.
Tom W Clark posted 01-09-2014 05:32 PM ET (US)
Skip the lanyard, bolt it to the transom. Why fool around?
dgoodhue posted 01-09-2014 09:14 PM ET (US)
I was in a boat when a clamped 25hp evinrude slipped off a transom during a swerve maneuver at full throttle. The motor violently thrashed around i. the water and the propeller cut the steering cable. The motor sunk to the bottom. It happened very fast. I would personally bolt it or atleast add a lip that will keep it slipping off like suggested in the posts above.
Peter posted 01-10-2014 09:43 AM ET (US)
Whatever you decide to do, make sure you put something under the motor bracket for the motor to rest on and I think that should be not simply be a loose block of wood. Unlike the bolt on transom brackets, the clamp-on motor bracket is designed to rest on the top of the transom even when the two bracket bolts are used.
skred posted 01-10-2014 10:36 AM ET (US)
Thanks for the observations from everyone. Most sensible - of course - is bolting the motor on. If I can get over my dislike of drilling a perfectly clean transsom - that's the way to go...

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Author	Topic: Small Outboard Motor Height
skred	posted 01-09-2014 10:31 AM ET (US) My 1981 Johnson 35 (remote) is mounted (not bolted) on my 1987 13 Sport in the normal fashion, but is somewhat lower than ideal (The cavitation plate is running below hull line). Without putting a jack plate or other commercially provided device on the boat, would it be unsafe to simply put a 1.5 inch block on the transom to raise the motor a bit? The standard attachment screws would still grip the transom, albeit nearer the top edge. This would give me the desired motor height. Would this plan somehow compromise the safety of the motor mounting?
Peter	posted 01-09-2014 10:56 AM ET (US) It could. You would need to bolt the motor on the transom. On the 13 Whaler, I've seen the screw clamps break loose causing the motor to jump off the transom in a sharp turn.
skred	posted 01-09-2014 01:29 PM ET (US) Did this problem occur on a motor with a spacer on the transom, or on a normally clamp-mounted motor, and did the clamp/clamps break or simply slide up and off the transom? I use a 3/8 inch thick x 4" x 16" flat piece of aluminum mounted with 4200 adhesive on the inside of the transom, with 2 holes for the clamp "pads" to rest directly on the transom. This has (for me) been a precaution against the motor clamps sliding up and off the transom. I suppose I could bolt the motor in position, but that's a hard decision to make on a "virgin" transom....
Peter	posted 01-09-2014 02:31 PM ET (US) The incident occured on a motor directly clamped to the transom. The round "washer" at the end of the clamp broke. It was not my boat but after seeing what happened, I drilled the two holes in the transom and bolted my identical motor -- a 1977 Evinrude 35 -- to the transom.
Buckda	posted 01-09-2014 02:41 PM ET (US) If you don't wish to put holes THROUGH the transom, you could get a 1/4 inch thick strip of aluminum and screw it to the transom above where the clamps grip. That would protect from the engine clamp slipping and having the engine "going rogue" on you. Also, be sure to always use a lanyard (chain is best) on a motor that is not bolted to the transom.
Peter	posted 01-09-2014 03:29 PM ET (US) Although the motor jumped off the transom, the old pulley and wire steering system kept the motor from going to the bottom. Likewise, a modern mechanical steering system should keep the motor from going to the bottom if it were to jump off the transom. Both are effectively lanyards.
skred	posted 01-09-2014 04:03 PM ET (US) Dave, Your idea is similar to my previous solution.. I have a 3/8 inch thick plate with 2 holes cut in it for the "pads" on the motor clamps, and the plate is adhered (4200) to the transom. The clamps cannot slide in any direction inside the holes. However, if one of the clamp pads breaks, that's another story. I'm just trying to get the motor up about an inch and a half without drilling and bolting the motor to the transom.
Buckda	posted 01-09-2014 05:31 PM ET (US) It is a much lower HP application, but on my inflatable, I have a block of wood between the 6hp engine and the transom top. That transom has a metal plate for mounting, with an upper lip that keeps it from sliding around... ...but I have had a 15 HP outboard jump the transom on a 14' MirroCraft that I had as a teenager. The lanyard saved the motor because, since it was a tiller-steer and I was 15, my self-preservation instincts kicked in and I went forward when the propeller came up. The engine ingested lakewater and stalled, and I was able to re-attach the engine and row home. On a bigger, heavier engine, I'd not rely on the steering system as a lanyard, but that's just me.
Tom W Clark	posted 01-09-2014 05:32 PM ET (US) Skip the lanyard, bolt it to the transom. Why fool around?
dgoodhue	posted 01-09-2014 09:14 PM ET (US) I was in a boat when a clamped 25hp evinrude slipped off a transom during a swerve maneuver at full throttle. The motor violently thrashed around i. the water and the propeller cut the steering cable. The motor sunk to the bottom. It happened very fast. I would personally bolt it or atleast add a lip that will keep it slipping off like suggested in the posts above.
Peter	posted 01-10-2014 09:43 AM ET (US) Whatever you decide to do, make sure you put something under the motor bracket for the motor to rest on and I think that should be not simply be a loose block of wood. Unlike the bolt on transom brackets, the clamp-on motor bracket is designed to rest on the top of the transom even when the two bracket bolts are used.
skred	posted 01-10-2014 10:36 AM ET (US) Thanks for the observations from everyone. Most sensible - of course - is bolting the motor on. If I can get over my dislike of drilling a perfectly clean transsom - that's the way to go...