Frequently
Asked
Questions

We recommend a 25:1 or 20:1 gas-to-oil ratio — that's 5 or 6 ounces of 100% synthetic oil per gallon of fuel. We recommend Amsoil Saber Pro or Honda HP2 oil.

Always use low-octane gas (87–89 octane). Do NOT use high-octane or race fuel — this can harm the engine. Once you choose your mix ratio, stick with it consistently.

During break-in (approximately the first 1.5–2 gallons of fuel), vary your running speed and avoid full throttle. Always be careful not to over-rev the engine.

Starting points for common Walbro carburetors used on Zenoah marine engines:

These are starting points only — fine-tune from there based on your engine's response and running conditions. Not sure which carb you have? Call us at 317-844-4695.

No more than 1 minute. Running longer risks overheating and serious internal engine damage. Be careful not to over-rev as well.

If you need to run longer — for break-in, tuning, or setup — connect a waterline from an external source to the engine's water inlet to keep it cool while running on the bench.

Zero Drag Seals install on both sides of the engine crankcase. They reduce drag on the crankshaft for improved RPMs and reduced engine wear.

Tools needed: Flywheel Puller, Zenoah Engine Tool (or same-diameter tubing), Hammer, and a small punch.

Output side (collet side): Slide the zero drag over the crankshaft with the tapered edge toward the seal. Press until it pops flush against the rubber seal face.

Recoil side: Remove the recoil, motor plate, flywheel, and the half-moon key from the crankshaft. Press the zero drag in flush. Reinstall the key, flywheel, plate, and recoil in reverse order.

We offer three header pipe shapes — each suited to different engine compartment configurations:

• 90-Degree — Standard bend, works well in most standard layouts
• Wrap-to-Center (WTC) — Routes toward the center of the boat, useful when space is tight on the sides
• Vee (V) — Splits to both sides, typically used in twin-engine configurations

The right choice depends on your hull size, engine placement, and tuned pipe routing. Call us and we'll help you pick the right one for your specific setup.

Zenoah marine engines have been the gold standard in gas RC boating for decades. Key advantages include:

• Purpose-built for marine RC applications
• Proven reliability across a wide range of hull types and sizes
• Extensive aftermarket support — replacement parts are widely available
• Highly modifiable — our BZ1, BZx2, and BZx4 engine modification programs are all built around the Zenoah platform
• Consistent power delivery across the RPM range

We stock Zenoah engines, replacement parts, and all major accessories. See our Engine section for the full lineup.

We offer three levels of Zenoah engine modification through our BONZI Sports performance program:

• BZ1 — Entry-level performance tune: port and polish, optimized carb jetting, break-in and test. Great for recreational racers who want noticeable improvement over stock.
• BZx2 — Mid-level competition build: all BZ1 work plus advanced porting, high-performance head work, upgraded carburetion, and dyno tuning. For club-level racers.
• BZx4 — Full race build: maximum performance extraction from the Zenoah platform. Competition-level porting, full head rebuild, race-spec carburetion, complete break-in and tuning. Built for NAMBA competition and serious high-speed running.

Not sure which level is right for your setup? Contact us at sales@bonzisports.com and we'll help you choose.

Not a defect — it's intentional. The lower-right hole and upper-right threaded hole on the Z-Plate have the anodized coating machined away for grounding purposes. The grey ignition coil must make a complete electrical ground through to the main crankcase, and the exposed metal ensures that connection is made reliably. Your plate is working exactly as designed.

Balance is critical for proper handling and getting your boat up on plane. On V-bottom boats, the balance point should be 27–30% of the total hull length, measured from the transom (back of the boat).

Example: a 50" boat should balance at 13.5"–15" from the stern. A nose-heavy boat may never get up on plane and will not handle correctly. Adjust the position of your battery, fuel tank, and other components to achieve the correct balance.

Yes — this is normal. The torque produced by single-engine gas RC boats creates a natural pull to the right. This can often be corrected or reduced with:

• Trim tabs — small adjustable plates on the transom that counteract torque steer
• Drive angle adjustment — changing the angle of the drive helps redistribute thrust
• Propeller change — different pitch or diameter can reduce the pull

If the pull is severe, call us and we'll walk you through the correct adjustment for your specific hull and engine combination.

A fail safe is an electronic device that plugs between the throttle servo and the receiver. It continuously monitors the radio signal and battery voltage. If either drops below safe thresholds — or if the signal between transmitter and receiver is lost entirely — the fail safe automatically closes the throttle to a preset idle position, stopping the boat from running away.

We highly recommend a fail safe for any boat running at speed on open water. A runaway gas RC boat at 50+ mph is a genuine safety hazard to people, property, and other boats. It's inexpensive insurance.

The general layout places the engine centered and forward in the hull, fuel tank behind or alongside it, radio box toward the stern, and water cooling lines running from the hull intake to the engine water jacket and back out through the exhaust or hull fitting.

Key considerations: component placement affects balance (see the balance question above), and all fuel and water lines must be routed to avoid kinks or chafing on moving parts.

For a visual reference, download our engine compartment layout diagram. If you're building from scratch, call us — we can walk you through it for your specific hull size and engine.

A clear water cooling system is essential for keeping your Zenoah engine at safe operating temperature. Blocked or restricted water flow leads to overheating and engine damage.

Weekly check: Blow through all water lines to confirm unrestricted flow. Look for kinks, cracks, debris, or buildup.

Salt water running: After every session in salt water, back-flush your entire water system with fresh water to prevent salt deposits from building up in lines, the water jacket, and fittings. This is one of the most common causes of heat damage in Zenoah engines and is easily prevented.

Speed varies significantly by hull type, engine, and propeller selection. As a general guide:

• Hydros and mono hulls with a stock Zenoah G260 typically run in the 40–55 mph range
• Cats (catamaran hulls) can push higher speeds due to reduced drag
• Larger hulls with modified Zenoah engines (BZx2 or BZx4) can exceed 60–70+ mph in optimal conditions

Prop selection has a major impact on top speed vs. acceleration. Ask us about prop recommendations for your specific hull and engine combination.

Yes — many of our hulls and engines are used in NAMBA (North American Model Boat Association) competition. NAMBA races are organized by engine size, fuel type, and hull type (hydroplane, mono, tunnel hull, etc.). Check your specific hull and engine against the class rules for your target NAMBA class.

If you're building or buying specifically for competition, call us and tell us what class you're targeting. We can recommend the right hull, engine modification level, prop, and drive setup to be competitive in your class.

Visit namba.com to find your local district and upcoming race events.

We offer two main types of drive cable systems:

• Solderless drive cable assembly — Uses a round collet to square ferrule connection. No soldering required, and the connection is actually stronger than a soldered joint. This is what we recommend for most applications.
• Solder-type assembly — A traditional configuration where the cable is soldered into a ferrule. Requires proper silver solder technique (see the soldering question below).

For a visual comparison of our shaft systems, view our shaft systems diagram. Still not sure? Call us — it's a quick conversation with the right details in hand.

1. Loosen the two set screws in the shaft ferrule (the tapered cylinder between the transom and shaft strut).
2. Loosen the cable collet compression nut — the 9/16" hex nut on the end of the collet.
3. Slide the propeller shaft toward the rudder until it is released from the ferrule.
4. Pull the ferrule down slightly until it clears the bottom of the strut, then pull the cable straight out the back.
5. Clean the cable, wipe off old grease, spray with penetrating oil to remove trapped water, re-grease, and store.

To reinstall, simply reverse the process.

• Soft-mounted engine (rubber dampened): approximately ¾" of clearance
• Solid-mounted engine: approximately ½" of clearance

This gap is essential. It allows the engine to move through vibration without the collet striking and damaging the end of the stuffing tube. Too little clearance is one of the most common causes of premature stuffing tube failure.

We recommend going solderless if possible. But if you need to solder:

Materials: Stay-Brite Silver Solder (comes with its own flux) and a propane torch with Mapp gas (burns hotter than standard propane).

Procedure:

1. Lightly sand the cable end and clean with acetone.
2. Apply flux to the cable and slide the ferrule over — the flux transfers to the ferrule interior.
3. Clamp the assembly vertically in a vise with the cable hanging down.
4. Drop 3 small pieces of solder (approx. ⅛" long) into the ferrule — they will rest on the exposed cable.
5. Heat the outside of the ferrule, working around the perimeter, until solder starts to melt and flow.
6. Pull the heat away immediately once solder flows. Direct heat to the cable removes its temper and causes failure.

Prop selection has a major impact on speed, acceleration, and handling. Key factors include:

• Hull type — hydros, monos, and cats all have different prop needs
• Engine size and modification level — a modified Zenoah needs a different prop than a stock one
• Desired performance — smaller diameter/higher pitch favors top speed; larger diameter/lower pitch favors acceleration and rough water
• Drive system — the specific drive you're running affects prop sizing

We carry ABC, Octura, and Prather props. For a starting point, check the BONZI prop recommendation chart, or call us with your hull and engine details.

We recommend Futaba 2-channel surface radios for most RC boat applications. Our RTR boats come equipped with a Futaba radio system. Key considerations when choosing a radio:

• 2.4GHz frequency — modern standard, reduces interference and eliminates the need for frequency pins at the pond
• 2-channel minimum — you need throttle and steering; some racers prefer a 3-channel for additional servo control
• Marine-rated servo — use a waterproof servo for the steering to handle splashing and water exposure
• Fail safe — essential for safety; see the fail safe question above

You can download the RTR Boat Owner's Manual (PDF) from the BONZI Sports website. If you have questions about a specific model or component that aren't covered in the manual, call us at 317-844-4695 — our team has been building and racing these boats for decades.

1. Remove all fuel. Siphon or pump out the fuel tank, then fire the engine and let it idle until it runs out — this purges the carb and fuel lines.
2. Fog the engine. Remove the spark plug. Pour approximately 1 oz. of lightweight cylinder lube (Marvel Mystery Oil works well) into the plug hole. Pull the starter cord 7–10 times slowly to distribute the oil through the rings, bearings, and cylinder. Reinstall the spark plug.
3. Service the drive cable. Remove it, clean off all old grease and any moisture or rust, lubricate, and reinstall.
4. Discharge batteries to storage level. Don't store rechargeable batteries fully charged or fully dead. A partial discharge (storage charge) prevents memory problems and extends battery life.
5. Protect all metal surfaces. Spray exposed metal hardware with WD-40 or similar penetrating oil and wipe down to remove moisture and prevent corrosion.

After each run, a few minutes of maintenance will significantly extend the life of your boat and components:

• Rinse the hull with fresh water, especially if running in salt or dirty water
• Drain and flush the water cooling system with fresh water
• Wipe down the engine exterior and radio compartment
• Check the drive cable tension and inspect the prop for dings or damage
• Check all water lines for kinks or loose fittings
• If the radio box has any moisture inside, open it to air dry before storing
• Store with the fuel tank empty or full — half-full tanks are more prone to fuel degradation and varnishing

We strongly recommend storing your boat indoors in a climate-controlled environment. Outdoor storage — even covered — exposes your boat to:

• Freeze/thaw cycles that can crack fiberglass hulls and fittings
• Condensation inside the engine and radio compartment leading to corrosion
• UV degradation of the hull finish and rubber/plastic components
• Rodent damage to fuel lines and wiring

If indoor storage isn't possible, thoroughly winterize the boat (see above), cover it tightly, and place it on a stand to keep it off cold concrete or damp ground. Ensure all fuel is removed before storage in any location.

Every RTR boat that leaves our shop is custom-built to order — we don't keep finished boats sitting on a shelf. Build and ship times:

• Standard RTR boats (non-inline Zenoah engine, no custom paint): typically 10 business days from payment confirmation
• Custom paint: adds approximately 1 week to the standard build time
• Engine modifications (BZx2, BZx4): may add additional build time — we'll quote you an estimated date at time of order
• Inline engine configurations: additional time required; ask us for a quote

We'll give you a confirmed estimated ship date when you place your order and will contact you if anything changes.

Yes — we ship to over 40 countries. International shipping rates are calculated at checkout for most items. For large or heavy freight items (such as crated RTR boats), we recommend contacting us at sales@bonzisports.com before ordering so we can provide an accurate freight quote.

International customers are responsible for any customs duties, import taxes, or fees charged by their country upon delivery. These are not included in our shipping charges and vary by destination. We ship all orders with full documentation to facilitate customs clearance.

Please review our full Terms & Conditions for complete details. In summary:

• Wrong or defective item received: Contact us immediately at sales@bonzisports.com or 317-844-4695 and we will make it right.
• Custom-built RTR boats: Because every boat is built to order, returns on custom builds are handled on a case-by-case basis.
• In-stock parts: Unused, uninstalled parts may be returned within 30 days in original packaging. Contact us first for a return authorization.

We stand behind everything we sell. If there's a problem, call us — we're not going to hide behind fine print.