Towing with motor up or down

[Pandy Girl]

We are going to tow our C-Dory for about 900 miles our dealer said to raise the engine up (90 Honda) let it rest on the engine lock, that would let the weight be down on the transom. If the engine was down all the weight would pulling back on the transom.
Which way would be best? Thanks
Jim

[Larry H]

Have you checked your owners manual?

[thataway]

On our 22 we had a strut from the lower unit to the trailer frame. Like:
http://www.veveinc.com/shop/customer/home.php?cat=18
There are also rubber wedges which take the weight of the motor.

On the TC we leave the engines all of the way down. On other boats I have put a wooden block between the transom mount and lower unit.

Either way, you will have weight on the transom. I have been told that one should not trailer with the "lock" taking the weight--but that may be incorrect.

[Bill.Secure]

If the motor is an "up" position, one possibility is that if you are rear ended while towing (as I was... see "It shouldn't happen to a dog"), the prop can go through the windshield and severely injure or kill the front seat occupants of the offending vehicle. It would have done so in this accident (and despite my feelings and fantasies about a non-insured, unlicensed driver who didn't know who owned the car he was driving and couldn't speak English), watching a body wheeled away on a gurney would have been a worse experience.

Since that incident, I've been trying to get a sense as to the factors entering into whether to tow "up" or tow "down". The only really solid argument I've seen in favor of "up" is minimization of transom strain. The folks that repaired my C-Dory claimed the transom as it came from the factory was exceptionally strong and that was why transom damage was minimal (therefore don't sweat transom strain). An additional con on towing up is that that the built in mechanism used to keep the motor in an up position may fail on a particularly harsh bump. An additional support seems to be required for towing up.

I'll be doing my towing (as I was at the time of the accident) with my motor in the normal operating (i.e. running) position. It may keep someone from being killed or injured, it means I don't have to mess with a special motor support bracket (to cope with that bump), and it makes my total tow train a bit shorter (which somehow seems an advantage).

I'm expecting to get my boat back this week at which time I will begin improving visibility of the rear of the towed boat using a number of LED add-on lights. I'll keep the C-Brats informed as to what I've done and how it seems to be working.

Bill Moseley
Edgewater, MD

[Dora~Jean]

When I towed my boat home for the first time from the dealer (500 miles), they had it in the fully tilted position with the built in engine lock rotated in place (Yamaha). One lock bracket failed during the trip (bent), engine was still up though, held by the hydraulic tilt mechanism and bent bracket. Yamaha sent me a new one free of charge (but no recommendations to avoid in the future).

I went out and bought transom savers that hook to the rear of the trailer and support the engines partially tilted up. A caution though, if you're going to use transom savers you MUST tie down the boat securely, especially at the stern or these 'sticks' could cause damage to the tilt mechanism. I've trailered over 8,000 miles now, no problems whatsoever.

Another method for short trips is to go ahead and use the engine lock brackets, but place some downward hydraulic tilt after rotating the lock in place to keep it from bouncing during trailering.

[oldgrowth]

I trailer my boat with the engine in the up position. After raising it, I flip the lock down then lower the engine until the stop/lock just touches.

With the engine down it is possible to hit the prop going through some dips, especially in parking lots. Also backing up you can hit the prop on curbs or other low objects.
________
Dave

[Notayot]

I'm with Oldgrowth. I tow with the engine "up" and the lock rotated and then slight downward hydraulic pressure. I have towed my last 3 boats this way, and never had a failure. Thousands of miles on I90, I5 and other lesser roads. I just don't like the idea of the prop and skeg being so close to the ground if not tilted up.

[RVP]

I was always told to leave the motors in the down position, the the weight is on the transom. The weight of the motors in the upright position is not good on the transom when the trailer bounces.

[Almas Only]

The Honda owner manual says to trailer with the motor down, using a support brace. I've never done that, and always trailer in the up position, after backing the motor tilt off to put a little preload on the two rotating support legs, while still keeping the tilt cylinders engaged, and therefore capable of taking a little force. The dealer told me to do it this way, and it makes sense. No damage has resulted after extensive trailering, and I don't like the thought of dragging the lower unit. I'll trail a strip of bright surveyor's marking tape tied to the prop, and seeing that at eye level has so far discouraged any other drivers from rear ending me.

As to weight on the transom, the weight of the motor is the same, no matter what position it's in. Therefore, the transom has to exert the same vertical force in each position. Essentially, the motor wants to compress the transom by pushing it down, and the transom exerts an equal vertical force on the motor. The angle of the transom from the vertical complicates this somewhat, but not all that much. The effect of the angle off the vertical is to introduce a twisting force on the transom.

However, when the engine is in the down position, all of the weight of the motor times the distance of the motor's center of gravity from the transom, exerts a moment (torque) force on the transom, which attempts twist the top of the transom off, toward the rear. With the motor in the elevated position, the head of the motor is in front of the transom, while the lower unit is extended to the rear. I haven't done a big calculation, but would be willing to bet that the moments of the head (now wanting to twist the transom forward) and lower unit (still wanting to twist the transom aft) cancal each other out to the extent that the net moment, and therefore net twisting effect on the transom, is reduced by trailering in the up position.

So, I'll just keep on truckin in the up.

[CAVU]

This was discussed at much length earlier. Search: towing up or down. Lots of opinions and good discussion.

[lloyds]

I'm with Oldgrowth. First trip, Wendy's parking lot, scrape. Only takes once. My book says to trailier it in UP.

[Pandy Girl]

Thanks All,
Looks like it is about 4 up & 4 Down, great to get all of the info. Ever one has a good reason for each up or down.
Almas Only thanks for getting into the real stress points of the transon. That is exaculy what the dealer told me about the transon.
Thanks all for input
Jim

[Dora~Jean]

Almas, I really like your explanation of the transom forces, matches what I've thought as well. I keep wondering about the proponents of trailering with the engine down, maybe it keeps the forces more stable -- albeit a constant torque on the transom. If tilted up with the force more directly over the transom, then maybe the moment arms of the head to the tip of the lower unit can cause large, undesirable fore and aft forces on the transom? Thoughts?

[thataway]

I might point out that on the Tom Cat with the engines down, there is plenty of road clearance because the bottom of the hull is over the trailer fenders , our experience with the CD 22, is that there was not enough clearance to avoid hitting the lower unit on the pavement.

[AKDAVE]

I just picked up my boat this afternoon after having the new motors installed. I asked the installer about his recomendation for my Suzuki. He recomended down as far as possible, all the way if road conditions allow. His reasoning was there would be less stress on the motor as it wouldn't have the tendency to see-saw. On my previous boat I always had the motor up all the way, mainly to have more ground clearance.

I'll have to figure this out this summer.