How to Choose the Right Starter Motor: 5 Checks Before You Order
Share
Two starter motors can look almost identical in a photo and still not fit the same engine. That is the most common reason a replacement starter goes back: it looked right. This guide walks through the five checks we recommend before you order a starter for an outboard, ATV, motorcycle or small engine. Every example below is taken from real starters in our own range.
Prefer to read? The full guide is below.
Why "it looks the same" is not enough
Starters for the same brand, and even for the same horsepower, often share a similar body. The differences that decide whether a unit fits are small: the number of teeth on the drive gear, the direction of rotation, the flange and bolt spacing, and the exact engine variant. None of these is reliable to judge from a picture, so check each one against your old unit or your engine documentation.
Check 1: Match the OEM part number
This is the single most reliable check. Look for the number stamped or printed on your old starter, or find it in your engine or parts manual. Then compare it with the OEM cross-reference table on the product page.
Example: our Honda BF75–BF150 outboard starter lists Honda 31200-ZY6-003 and 31200-ZY9-003, plus Mitsubishi M0T60981, Arrowhead SMT0374 and J&N 410-48148. If your number appears in the table, you are almost certainly looking at the right part.
Check 2: Count the teeth on the pinion
The pinion is the small drive gear at the end of the starter. Count its teeth and compare with the specification on the listing.
Example: two starters for a Mercury 90HP.
- The Mercury/Mariner 50–90HP starter (1972–1999) has a 10-tooth pinion and a direct-drive (PMDD) design.
- The Mercury 75–115HP 4-stroke EFI starter, which covers the later 90HP engines, has a 14-tooth pinion and a gear-reduction (PMGR) design.
Same brand, same horsepower, different part.
Check 3: Rotation, clockwise (CW) or counter-clockwise (CCW)
A starter that turns the wrong way will not start the engine, even if the teeth and mounting match. Rotation is always stated in the technical specs on our listings. Compare it like for like with the old unit.
Example: both of these Yamaha ATV starters have 9 teeth:
Check 4: Compare the mounting
Check the flange shape, the distance between the mounting bolt holes and where the power terminal sits. A starter can have the right gear and rotation and still not bolt on.
Example: on our Honda GX610 / GX620 / GX670 starter the mounting holes are 66 mm apart (centre to centre). Measure yours before you order.
Check 5: The exact model and year
The model name alone is not enough. Manufacturers often change the starter within the same model family.
| Engine | Years | Starter |
|---|---|---|
| Honda TRX350 Foreman | 1985–1986 | 10 teeth, CW |
| Honda TRX350 Rancher | 2000–2006 | 9 teeth, CCW |
| Honda BF115 outboard | 2011 onwards | 31200-ZY6-003 type |
| Honda BF115 outboard | Before 2011 | Different starter, not covered by the unit above |
Quick checklist before you order
- Part number: is your OEM number in the cross-reference table?
- Teeth: does the pinion tooth count match?
- Rotation: CW or CCW, same as your old unit?
- Mounting: flange, bolt spacing and terminal position?
- Model and year: does your exact engine variant appear in the fitment guide?
FAQ
What is the difference between PMDD and PMGR starters?
PMDD (permanent magnet direct drive) starters drive the pinion directly from the motor. PMGR (permanent magnet gear reduction) starters use internal reduction gears for more torque. They are usually not interchangeable, so match the type shown in the specs.
I can't read the number on my old starter. What now?
Use the engine's model, year and serial number to find the part in your parts manual, then check teeth, rotation and mounting against the listing. If you're still unsure, send us what you have.
Will a starter with the same number of teeth always fit?
No. Rotation and mounting must match as well. See the Yamaha example above: same tooth count, opposite rotation.
Not sure which starter you need? Send us your part number or a photo of your old starter before you order. You can also browse all starter motors or read our Starter Motors FAQ.