And it seems like a simple task to install a outboard motor, to screw the traverse, to lock the engine, and you can go out into the water. 80% of problems with outboard motors This is due to the wrong attachment: vibrations on the move, corrosion of the fastener, skewed transom or even engine tear when abruptly maneuvered, especially critical for PVC boats, where a weak transom can deform under the weight of a powerful motor, and for aluminum boats with thin sides.
In this article, we will understand fixation - from standard traverse to reinforced homemade structures, we will dwell in detail on the choice of bolts and sealants, and also show how to avoid common error with the "cruising" transcen, which leads to premature wear of the motor gearboxThe material will be useful to both beginners and experienced boaters who want to optimize the installation for a particular model of boat and engine.
1. Types of fasteners: which traverse to choose for your boat
Travers (or) motor-arc) is the main element that connects the motor to the transom of the boat, and the choice depends on three key parameters:
- 🔹 Materials of the boat - PVC, aluminum or fiberglass (for the latter, special gaskets are needed).
- 🔹 Engine power - up to 10 hp. suitable standard traverse, for 15+ hp requires a reinforced design.
- 🔹 Type of transom - rigid (aluminum / plastic) or inflatable (for PVC boats).
For most PVC boats with inflatable transcrete optimal traverse (for example, Honda Marine or Yamaha) adjustable width: lightweight, resistant to corrosion and allow for precise engine positioning; for aluminum boats, it is better to choose steel traverses with anti-corrosion coating (for example, Mercury Marine) because they withstand a great deal of load and vibration.
If your boat has transmutant (for example, rounded or with a cutout for an outboard motor), you will need to universal traverse with flexible fasteners Or a homemade stainless steel structure, and note that motors over 30 hp are often required. transaxialization We will talk about this in the section on errors.
2. Step-by-step instruction: how to fix the motor on the traverse
Before you start installing, make sure you have everything you need:
Set of bolts and nuts (stainless steel A4-70 or A4-80) | Hermetic for water-resistant joints (for example, Sikaflex-291>) | Screwdriver or screwdriver with bolt attachment | Line or roulette for alignment | Key dynamometer (for precise tightening)->
We shall now proceed to the installation:
- Markup. Put a traverse on the transom and mark the holes with a pencil. Use PVC boats.
stencilThe distance between the holes must strictly comply with the standard of the motor (usually 76-114 mm). - Drilling. Use it for PVC. drilling is 1-2 mm smaller than the diameter of the boltFor aluminum boats, drill holes under the M8-M10 bolt with a puck-core rod.
- Bolt installation. Slide the bolts through the traverse and the transom, put on the washers and nuts. Don't drag it out! First, make all the mounts, then level the traverse.
- Sealing. Apply the sealant to the bolt thread and the traverse adjacent to the transom. polyurethane sealantfor aluminum. thread-holder (for example, Loctite 270).
- Puff. Tighten the cross-cross bolts, starting with the central bolts. The puff moment for the M8 bolts is 15-20 Nm, for the M10 - 25-30 Nm. The tufting can deform the transom!
After installation, check power-train: it should be smoothly rotated up and down without jamming. If the backlash is too large, add rubber or plastic gaskets between the traverse and the transom.
Before the first launch, lubricate the bolt thread graphite-lubricant This will prevent the nuts from getting stuck after contact with water.
3. Fastening elements: what bolts and nuts to use
Mistakes in choosing a fastener can turn engine-break Or transom corrosion. Basic bolt requirements:
- 🔧 Material: stainless steel AISI 316 (A4) or seawater titanium alloys. The usual A2 stainless steel rusts quickly in salt water!
- 🔧 Diameter: M8-M10 for engines up to 20 hp, M12+ for powerful engines (from 30 hp).
- 🔧 Length: The bolt should protrude above the nut by 3-5 mm after tightening (for installing a grower).
- 🔧 Pucks: definitely use grover's spring-puck Or locking with teeth to prevent self-twisting.
For PVC boats, bolts with hooded (for example, bolts with flange) which distribute the load evenly on the material. hexa-head DIN 933 – These are more securely fixed with the key.
| Type of boat | Recommended bolt | Moment of tightening (Nm) | Hermetic |
|---|---|---|---|
| PVC (inflatable transom) | M8 A4-70 with 24mm puck | 12–15 | Sikaflex-291 or 3M 5200 |
| Aluminum (traffic 3-5 mm) | M10 A4-80 with Grover | 20–25 | Loctite 243 (for threading) |
| Fiberglass | M10 titanium with gasket | 18–22 | BoatLife Life-Calk |
| Hard transom (wood/plastic) | M8 galvanized with puck | 15–18 | Tectil 2500 |
⚠️ Attention: Never use it. cock-bolt (Durability grade 4.8 or 5.6) – they rust in 1-2 seasons and can break when loaded. aluminum rivet for fastening the traverse: they do not withstand the vibration of the motor.
4. Seal sealing of compounds: how to avoid leaks
Even a small gap between the traverse and the transom can lead to leakage In the boat or corrosion of aluminum, proper sealing involves three steps:
1. Surface preparation. Clean the transom and traverse from dirt, defat acetone or white-spiritFor PVC, further clean the surface. sandpaper (400 grit) for better grip.
2. Sealant application. Use it. polyurethane or MS-polymer sealants (for example, Soudal Fix All or 3M Marine Adhesive Sealant 5200Apply a thin layer (2-3 mm) around the perimeter of the holes and at the junction of the traverse with the transom. silicone sealants They do not hold on to PVC well and peel off over time.
3. Puff and dry. After applying the sealant, immediately tighten the bolts (do not let the sealant freeze), then remove the excess with a wet cloth. Complete drying takes 12-24 hours - at this time you can not operate the boat!
You can use additional protection for butyl-rope (for example, Butyl Tape) It's glued onto a traverse before installation, and this is especially true for boats that are often transported by trailer (vibration destroys the sealant).
What if the sealant leaks inside the boat?
If a sealant (e.g., 3M 5200) hit the inside of the PVC boat, do not attempt to scrape it off with a knife, it will damage the material.
1. Let the sealant freeze completely (24-48 hours).
2. Carefully cut the main layer scraper (not metal!)
3. Remains removed polyurethane solvent (for example, Soudal Remover), applying it for 5-10 minutes.
4. Wash the place with soap and water and dry.
5. Typical errors in the fastening of the motor and how to avoid them
Even experienced boaters sometimes make mistakes that lead to the engine failure or boat-damageHere are the most common ones:
❌ The traverse skews. If the traverse is unevenly mounted, the motor will vibrate and the gearbox wears out faster. How to check: use bubble-level or apply the motor to the transom - the gaps should be the same on both sides.
❌ Weak bolt tightening. Vibration on the move gradually unwinds the nuts, which can lead to the loss of the motor. Decision: use lock-carving (for example, Loctite 243) and check the puff before each watering.
❌ Lack of pads. A metal traverse pressed directly against PVC or aluminum will wipe the material over time. Correction: set up rubber-stick (thickness 2-3 mm) between the traverse and the transom.
❌ Wrong choice of bolts. Bolts made of "black metal" rust during the season, and too long bolts can pierce through the transom. Right: stainless steel A4, bolt length = transnec thickness + traverses + 5 mm.
❌ Ignoring the backlash. If the motor is "cruising" in the mount, this leads to shaft-wear and leaks of gums. What to do: Pull up the bolts or add pads for a tight fit.
⚠️ Attention: If after installing the engine the boat became worse to control (takes aside), check anchorageOften the problem is that the traverse is shifted relative to the boat's center of gravity, corrected by a 1 to 2 cm left/right shift of the motor.
The most dangerous mistake is the use of squirrel-freeThe vibration of the motor spins them in 2-3 exits to the water, which can lead to loss of the engine on the go.
6. Trans amplification for powerful motors (from 20 hp)
Motors over 20 hp put a significant strain on the transom, especially when overclocking. PVC boats and aluminum boats with thin transom (< 4 mm) require reinforcementLet's look at two proven ways:
🔧 Method 1: Installation of transoms boards. For PVC boats, they use plywood It's 10 to 15 mm thick, and it's bolted inside the transom, and it spreads the load over a larger area. waterproof (sea plywood or DSP plate).
🔧 Method 2: Enhance the metal profile. For aluminum boats welded 30x30mm corner perimeter of the transom or set cross-ribbonWelding must be performed by a specialist, so as not to burn out thin aluminum.
For boats with inflatable transom (e.g., Zodiac or Bombard) exist transom reinforcement of composite materials (e.g., Transom ShieldThey are glued to the transom with epoxy glue and increase the strength by 2-3 times.
Before strengthening the transom, be sure to check maximum permissible power of the motor for your boat model (specified in your passport) exceeding this value may result in transmutation even with the boost!
Maintenance of the fastening: how to extend the service life
To ensure that the engine mounting lasts for many years, follow these recommendations:
- 🔄 After each launching: Wash the traverse and bolts with fresh water to remove salt and sand.
- 🔧 Once a season: Check the moment of tightening of the bolts (they can weaken from vibration).
- 🧴 Every 2 years: Update the sealant at the junctions of the traverse and transom.
- 🛠️ When rust appears: clear the bolts rust converter (for example, WD-40 Specialist) and apply a new lubricant.
If you keep a boat outdoors in winter, take off the engine And traverse, and this will prevent the corrosion of the fastener and the deformation of the PVC from frost. preservative (for example, Liqui Moly MoS2).
When transporting a boat on a trailer lock the engine in the upper position with screeds - this will reduce the load on the traverse and prevent its deformation from impacts.
FAQ: Answers to frequent questions
Can I attach the motor to a PVC boat without a traverse, directly to the transom?
No, it's extremely dangerous! The PVC boat's trawler is not designed to carry the pinpoint load from the bolts -- it will eventually be worn out, and the motor may come off. The traverse distributes the load and protects the material. squirt (for example, Zodiac Medline), but in this case, manufacturers recommend the use of a traverse.
Which sealant is best for salt water?
For sea water optimal polyurethane sealants (Sikaflex-291, 3M 5200or MS polymers (Soudal Fix All CrystalThey're resistant to salt water, UV radiation and vibration. Silicone sealants (e.g., Moment Herment) are not suitable - they do not stay well on wet surfaces and quickly break down.
What if the bolts rust and do not unscrew?
1. Pour bolts profusely penetrating (WD-40 Specialist or Liqui Moly Rostloser) and leave for 12-24 hours.
2. Try to unscrew. screwdriver or extension-head (for more leverage).
3. If the bolt breaks, drill it out. left-handed or use jack-up.
4. After removal, clean the thread pointer And install a new stainless steel bolt.
Do I need to remove the engine from the traverse for the winter?
It's desirable, especially if the boat is kept outdoors, so it's not going to be:
- Condensate bolt corrosion.
- Deformation of the PVC transom under the weight of the motor.
- Getting moisture into the motor reducer (at temperature changes).
If you are not comfortable taking off the engine, at least Put him up in the top position. And treat the attachments with preservative lubricant.
Can I use one traverse for two engines?
Technically possible, but not recommended without translacing. Two motors create symmetricalwhich leads to:
- Mismatching the traverse and vibration.
- Accelerated wear of gear bearings.
- Risk of mounting separation during sharp maneuver.
If you need to install two engines, use them. cross-beam (for example, MotorGuide Xi5) and reinforce the transom with an aluminium profile.