[Originally published in the Jaunary 2022 issue of Ski-Boat]
By Erwin Bursik and Ryan Hansen
THE question is often raised as to how those of us who tow our ski-boats should secure the outboard motors while we’re towing. Seeing that one’s outboards make up the greater part of one’s rig’s value, it’s best to secure them correctly to ensure that they don’t get damaged and that the craft’s transom doesn’t endure more stresses than it is designed to take.
In the past, before the days of hydraulic trims that most, if not all, of the bigger horse powered motors have as standard, a simple manual lever flipped into position to stop a tilted motor from falling back into its vertical position. As this could and did easily happen, most of us towing craft at that time had a conglomeration of ideas and methods of ensuring that our motors were protected.
This is especially important when one considers the road conditions back then, especially the old Sodwana and Cape Vidal roads, as well as the pre-war Moçambique roads from the border to the northern areas such as Tofo and Vilanculos.
Innovative ideas — ’n boer maak ’n plan — were plentiful. From wooden planks placed between a tilted motor and transom bracket, to engineering marvels that cradled the motors’ lower shaft in the desired position with the lower part of this stantion secured to the trailer. Much rope and/or a clamping system thus ostensibly prevented one’s motors from bouncing around and putting undue strain on the craft’s transom.
Many pundits of the time spoke strongly against firmly tying or bolting one’s craft to its trailer as it was construed that the stresses the trailer experienced on rough roads were then directly transmitted into the hull of the craft it was carrying.
This practice is used extensively even to the present, and often makes one wonder whether the trailer is supporting the boat or the boat is supplying the rigidity to a poorly manufactured trailer.
That aside, and to avoid any red herrings being thrown into the equation, the primary concern was to prevent one’s motors from bouncing up and down on the vertical axis, and at the same time preventing the gearbox casing and propellers being damaged. There was also a concern that any movement during a long tow would put undue pressure on one’s transom.
When hydraulic trims became the norm, skippers then set their trims to whatever level they considered to be sufficient to prevent damage to the outboard motors, skeg, gearbox and/or propellers. The trust was put in hydraulics to provide the necessary safety and security.
Due to some skippers’ experiences, and others who question this over reliance on the strength of the mechanics in question, the wisdom of this practice has come under debate. Some feel that the vibration and bouncing of the rig on the trailer puts undue pressure on parts that have not been designed to withstand the rigours of long distance towing.
After all, the motors are designed to work on the aft of a craft with the hydraulic piston and ram doing its job of raising and lowering, i.e. trimming, the craft while in motion and then, when it’s not running, lifting the entire unit out of the water, utilising its two action hydraulic rams for trimming while running and the second for fast trimming while mooring or trailering.
Of course it must also be construed that the craft’s transom will have or should have been designed and built to withstand all the stress it and the hull has to withstand. There’s a lot to endure from the time it is dropped onto a beach or shorebreak, to the shakeup and banging it is subjected to over when running through the surf and over waves. Thereafter a long run at sea also tests the motors and their attachment points to the transom and the strength of the transom itself.
The final high speed run up the beach on one’s return must also put enormous strain and torque on both the motors attached to the craft as well as the transom. This is exacerbated when the hydraulic ram has to take the enormous shock as the craft slides up the beach. Beaching kits installed in the hydraulic rams allow for this, but both the motors and the transom undergo enormous stresses during those last few seconds of beaching.
During this latter scenario of beaching, one mostly has no control, but with the high number of craft executing this procedure every day, we just accept that the combination of motor hydraulics and transom design simply “works”.
However, we have more control over the often long and bouncy tow of our rigs, so we need to do what we can to ensure that after a long tow to Moçambique the motors and the craft’s hull and transom remain damage free.Ryan Hansen of Durban Yamaha is acutely aware of this problem and has provided SKI-BOAT magazine and its readers with what he believes is the most practical method of securing both craft and motors during any towing undertaking. Over to Ryan…
First and foremost, the flip lever or lift button on some models is there primarily to ensure the motor is tilted right up and held in position while the motor is being serviced and repaired, not to hold it up when towing. A quick look at this lever will show it is not over engineered to withstand the motor bouncing up while being towed.
Granted, one might say that on the current models with hydraulic trim rams one can set the flip lever and then set the trim to just hold the position. This may work for short tows, but is not ideal for the long runs.
Furthermore, the beaching kits adaption of trims enables the motors to kick up from vertical to nearly horizontal to enable high speed beaching. This action could be activated by severe bouncing of the craft if one hits a bump or pothole during high speed towing.
Another argument is that the hydraulic trim rams are engineered to withstand such pressure loads and, in most instances, have a two stage or double action ram that uses the lowest position and slowest for trimming one’s craft whilst under power at sea, and the secondary phase of lift for faster final trim to lift the lower unit out of the water into its full up position.
Ideally the hydraulic trims should be robust enough to hold partially- or fully trimmed outboards for towing. While that might be so for long distance towing on first world state highways, the roads in South Africa and especially Moçambique are a totally different matter. Any bouncing on the rougher roads can and will cause excessive wear on the ram rod seals and even the ram rods themselves.
This is the broad scenario covering a wide spectrum of uses and towing scenarios, and as such each boat owner should adjust his thinking according to the road conditions he is likely to encounter while towing his own rig.
Since time immemorial, many different devices have been used to support motors for long distance towing. From hard wood branch off cuts and short lengths of hard wood, to — in desperation — one’s shelele or kill baton. The more sophisticated skippers take a square bar of Teflon and neatly and easily drill holes for ropes to go through for easy deployment.
The best and arguably the quickest, easiest and most effective devices are the commercially available adjustable mounting bars that attach to the aft trailer frame and cradle the motor’s lower unit in a padded forked or V- shaped mount that has stretch straps for additional security. (See accompanying photographs.)
Still on the table and under debate is whether one should tie the craft to the trailer frame for towing. Whilst all trailers have heavy-duty leaf springs and virtually none have shock absorbers, any bouncing of the trailer is transferred to the craft itself. The conundrum is, is the boat supporting the trailer or the trailer its boat?
The craft’s hull is designed to withstand the rigours of on water use, not really being bounced on its trailer over rough roads. The two lines of thought are that if the craft’s keel is supported on a bed of rollers and supported fore and aft by turnbuckles or straps, any trailer movement is dissipated along the entire length of the craft’s hull and most stresses induced from road to trailer are largely negated. Furthermore, the quality and framework of today’s quality trailers ensures minimal lateral and longitudinal bending or twisting.
My personal opinion is that bow and transom restraint turnbuckles (held in position by rigid galvanised wire rather than plastic cable ties) and a forward movement-restraining chain attached to the bow cleat allows only a small degree of craft-on-trailer movement. After ten years of towing, mostly up to Guinjata in Moçambique, I have not experienced any hull damage or apparent stress cracking in areas of the hull that are acting as retention points.
A large number of craft are towed over some of those horrendous roads, all virtually using the same or similar tie down methods I just described, and as far as I know, no major adverse reports of hull damage have surfaced.
For me this is proof that after many, many years of thought and practical application, we have a system that works well for our situations here in South Africa.