Bravo

Can I work out my Bravo ratio from the upper unit alone?

No - and this is the mistake we see most often on Bravo orders. There are only three SEI uppers and each is used at several different ratios: the 30/23 upper, for instance, appears on a 1.65, a 2.20 and a 2.43 drive. The ratio comes from the upper and lower gear sets together, so you need the tooth count from both halves, or the drive serial number. Getting it wrong is expensive - once the drive is bolted up it cannot be returned. Call or text us at 813-925-7127 with the serial and we will confirm it.

Do all Bravo transom assemblies accept any Bravo drive?

Yes - all the Bravo transoms will accept a Bravo One, Two or Three. That's why going from a Bravo Two to a Bravo Three is a common swap physically. The thing that isn't interchangeable is the gear ratio and propping, which is where you need to be careful.

Does the Bravo One lower unit come in different gear ratios?

No - Bravo One lowers are built in a single ratio, unlike Bravo Three lowers which come with different gearing options. The only choice to make on a Bravo One lower is the water intake configuration: 90-121-02 is side intakes only, and 90-122-02 is side plus low water intakes.

How do I confirm a Bravo Three 2.20 ratio by tooth count?

Strip and count both sets: the driveshaft housing assembly gear set at 30/23 and the gear housing assembly gear set at 16/27 together confirm a 2.20:1. Bravo Three ratios are determined by both the upper and the lower, which is why we ask for the drive serial number or counts from both halves. We see a lot of mistakes on Bravo Three replacements where the ratio isn't right, and once bolted up they can't be returned.

How do I identify my Bravo drive and gear ratio from the gear counts?

How do I tell if my Bravo One lower has single or dual water intakes?

Dual water intakes have pickups on the leading edge of the gearcase in addition to the side intakes. If all you have are the side intakes, that's the single. It's the one thing we need to know when ordering a single-prop Bravo One lower - and usefully, the single and dual versions interchange without fitment issues.

How do I tell whether my Bravo One has single or dual water pickup?

A dual water pickup has additional pickups on the leading edge of the gearcase. If all you have is the holes on both sides that the ear muffs cover, that's a single pickup. Usefully, the single and dual Bravo One lowers can be interchanged without any fitment issue, so it isn't a decision you can get badly wrong.

My new Bravo lower has an oil passage hole that my upper doesn't - what do I do?

That hole benefits cooling on the upper through oil circulation. The old modification of drilling and plugging to match is something we no longer support under warranty. If your upper doesn't have the mating hole, the modification is acceptable if needed - but we'd never suggest going the other way and plugging an upper, because the upper benefits significantly from that additional cooling. The newer Bravo Three lowers have the oil recirculation hole as standard.

What are the bump rings in a Bravo drive?

The bump rings are the brass rings in the upper unit that the clutch fork "bumps" against to bring a Bravo out of gear. It's not unusual for the clearance to be tight on a new unit, which is part of why a new Bravo can feel firm shifting until it's broken in.

What's the difference between a Bravo Three 2.00 and a 2.20 ratio drive?

The lower unit is the same for both - it's the upper that changes. For the 2.20 ratio you need the 90-121-01A upper rather than the 90-121-01B used for the 2.00. Spline counts are identical across them, so there's nothing else to worry about there. The ratio doesn't change the price either.

What's the difference between the SE121 and the SE128?

The SE121 is the Bravo upper unit and the SE128 is the Bravo Three lower. All Bravo uppers are the same apart from gear ratio (and the older-style MerCruiser gearcase from the 1990s), so it's normal to see SE121 stamped on the upper of a boat running a Bravo Three lower. Our SE121 uppers are the aftermarket replacement for Mercury's current version, the one referred to as "swept back".

Where is the serial number on a Bravo drive?

There are separate numbers and mixing them up is the most common problem we see. On an SEI unit, the serial is on a red tag inside the upper and the lower, and the same number is stamped into the case - our sales team can look that number up and tell you exactly what the unit is. On a MerCruiser drive, the drive serial is on the drive itself; the number on the transom bracket is the transom assembly serial, which is a different number and won't give us your gear ratio. If you're not sure which you're looking at, send us a photo at 813-925-7127.

Will you recommend which Bravo gear ratio I should run?

We don't advise on ratio selection - what we do is confirm the ratio you already have so the replacement matches. Boat builders choose the gear ratio and prop together based on the hull, so if you're changing drive types the builder (or Mercury Marine for Brunswick boats) is the right place to ask. Send us your drive serial number and we'll confirm your current ratio exactly.

Cobra

There were two prop shaft sizes on my OMC case - which seals do I need?

That case was built with two different prop shaft designs, a 1-3/16" and a 1-1/4" outside diameter, and the seals differ between them. Measure your shaft before ordering. We sell the inner and outer prop shaft seals individually as well as a complete seal kit for the whole lower unit, which is usually the better value if you're in there anyway.

What's the difference between a 400 series and an 800 series OMC Cobra gearcase?

They're two different gearcase sizes OMC used. The 800 series is the 4.750-inch diameter gearcase. The most reliable check is to measure your gearcase, but as a rule if you have a V6 or V8 engine it should be the 800 series. Parts listed as "800 series only" won't fit the smaller case, so measure before ordering.

Diagnosis

My driveshaft wiggles side to side at both ends - is that a problem?

That's normal. A small amount of side-to-side movement at the motor spline end and the impeller end is expected and isn't a sign of a worn unit. If you're hearing a noise you're unhappy with, the meaningful test is to run it in the water under load and then reassess.

My new lower unit feels stiff to turn - is it shimmed wrong?

Almost certainly not. A new gearcase with new bearings has noticeably higher rolling torque than the worn unit you took off - that resistance is normal and eases as it beds in. Measure it with the water pump off, because the impeller makes any shaft hard to turn and misleads people constantly. Rolling torque specs differ between units, so rather than work to a general figure, call us at 813-925-7127 with your unit and we'll give you the spec that applies to yours.

Gear Set

What does the dimension listed on a gear set refer to?

On our gear set listings, a dimension such as 3.26 is the outside diameter of the bearing race, not the width of the forward gear. If you're matching a gear set to an existing gearcase, measure the bearing race outside diameter to compare. Send us the gearcase model and we'll confirm which set fits.

Johnson Evinrude

Is the SE306 the same as a Magnum or M2 gearcase?

No. The SE306 is a different gearcase from the Magnum and Magnum 2 - our unit for those is the SE316. They look similar enough in photos that they're easy to confuse. Send us the full engine model number and we'll confirm which gearcase you actually have before you order.

Mercury

How do I know if I have a Torque Master or Sport Master gearcase?

The giveaway is the prop shaft. The Torque Master, Torque Master 2 and Sport Master all use the "Fat Shaft" prop shaft with 19 splines, whereas our SE221 has a 15-spline prop shaft. Those three gearcases are ones we don't replace. If you fit one of ours to an engine originally built with a Torque Master it would be sold without warranty, and you'd need a prop hub change to suit the smaller shaft. Send us the engine serial number and we'll tell you which gearcase it left the factory with.

How do I tell whether I have a 4.8-inch or a 5.44-inch gearcase?

The number is the diameter of the torpedo - the bullet-shaped housing the prop shaft comes out of - so the two are 4.8 inches and 5.44 inches across. It's the first thing we ask, because we make the 4.8 and we don't make the 5.44. If you'd rather not measure it, send us the outboard serial number or a clear photo of the gearcase and we'll identify it for you. Worth doing before you order rather than after: fitting a 4.8 to an engine that called for a 5.44 means no warranty.

Is an SEI lower unit a Torque Master?

No - if you have SEI lower units, they are not Torque Masters. That matters when you're sourcing gears or parts, because the Torque Master is a different gearcase with different internals. Note also that our forward gear is not dimensionally identical to the Mercury OEM forward gear, so OEM gears aren't a drop-in for our unit.

Water Pump

How do I tell which Alpha water pump base I need?

Measure the base - the newer style is around 60mm and the older style is slightly smaller at around 58mm. The undersides of the two are also different, so if you still have your original base, comparing them side by side is the most reliable check. Send us your measurement and we'll confirm which one to send.

My old water pump base came apart when I removed it - what now?

Look into the lower unit where the base sat: you'll still see some black plastic and a seal left behind. That has to come out of the lower unit before the new base will seat properly. The replacement base we supply comes with new seals for that area, so you don't need to source those separately.

Will the water pump kit fit my original older Alpha lower?

Check before ordering - the O-ring and gasket in the complete kit are for the newer Alpha. If your lower is the original older unit you'll need the older-style base instead, which has the correct O-ring and gasket for it. Measure the base (roughly 58mm for the older style versus 60mm for the newer) or send us a photo and we'll confirm which you need.

Yamaha

I can't find my Yamaha lower unit by its OEM part number - do you not make it?

Not necessarily - we identify Yamaha lower units by engine model number rather than by OEM part number. Put your model number into the search bar at the top of the page and it will take you to the correct unit if we make one. Then check the technical tab on that product page and confirm your model number and year are both listed. If it doesn't come up, text us the model number and we'll check directly.

What information do you need to identify the right Yamaha lower unit?

We work from the full engine model number - something like F250TXR or LF150TXR - not just the year and horsepower. That model number carries the stroke type, shaft length and rotation we need to match the unit. If your ID tag is gone, send us a photo of the bearing carrier behind the prop and tell us the shaft length, and we'll work from that.

Yamaha gave me a different part number than the one on your unit - is yours wrong?

Almost certainly not. Yamaha issues a new part number for even a slight colour change, and numbers supersede frequently, so a chain of different numbers can all describe the same gearcase. What actually matters for fitment is the shaft splines, the shaft length, the gear ratio and - on some models - whether it has the water-cooled bearing carrier. We match on your engine model number rather than the OEM gearcase number, and we've sold thousands of these against it.