Alpha Gen I Three-Bellow Kit Fits MerCruiser Alpha One Gen I Sterndrives 1983–1990, Exhaust Tube 78458A1 + U-Joint 60932A4 + Shift 74639A2

Drive's off for transom work? This is the Gen I three-rubber set most Alpha One owners replace together — exhaust tube 78458A1, ridge U-joint 60932A4, shift 74639A2. One box, three boots, replaces OEM kit 30-803097T1.

Built for MerCruiser Alpha One Gen I (1983–1990, serial 06225577 thru 0D469858 — check your drive tag). Rubber only. No bearing, no gasket overhaul hardware.

Why grab all three at once?

Because pulling the drive is the part that ruins your weekend. Once it's off, you're already in there — might as well swap aging rubber while you can reach it. All three boots bake in the same hot, salty transom. One cracked, soft, or oily boot? The other two are usually right behind it.

This kit lines up the three Gen I numbers you're actually looking for (78458A1 + 60932A4 + 74639A2) so you're not guessing parts or scheduling round two next season because you left old rubber behind.

Wrong generation? 1991+ Gen II → 18BK003. Bravo drive → totally different kit. Engine size won't save you — serial number will.

Only one boot actually failed? Exhaust tube leaks are the usual suspect — grab 17B1015. Just the ridge U-joint boot → 17B1004. Shift only → 17B1005. Already swapped the other two last year? Singles are fine.

What's in the box

Three boots, three locations on the drive — need just one? We sell each piece separately.

Component	OEM	Cross-ref	GH single SKU	Qty
Exhaust tube / bellow	78458A1	18-2760 / 89150	17B1015	1
U-joint bellow (ridge)	60932A4	18-2751 / 89050	17B1004	1
Shift cable bellow	74639A2	18-2753-2 / 89080	17B1005	1

 

Which kit is this, really?

Real talk: this is the old-school Gen I three-bellow rubber kit — OEM family 30-803097T1, Sierra 18-8213, GLM 21965. The set you want when the drive's off and you're doing transom rubber, not a full bearing rebuild.

Not the 1991+ Gen II kit (18BK003 / 30-803099T1). Not the bearing+gasket monster pack some suppliers photograph (17B3005 territory).

Kit or singles — what would a shop guy tell you?

Get this kit if:

·       The drive's already off — don't leave two tired boots in there

·       Your annual peek shows two or more boots cracked, soft, or shiny with oil

·       Bilge water after a run and you're not sure which boot — plan for all three

·       You want all three Gen I part numbers showing up in one box

Grab a single instead if:

·       Only one boot failed — exhaust tube is the common one → 17B1015

·       You replaced the other two last season and they're still solid

·       You're topping off shop stock on one number

Sold separately either way: marine bellows adhesive · expander 22ET001 · sleeve driver 21B1001

Signs you're probably due for all three

·       Bilge smells like the lake again after a run — any of the three transom boots could be the leak.

·       Annual look-see: more than one boot cracked, soft, or weeping oil — swap the set before you launch.

·       Drive's off anyway — labor's already sunk; skipping the other two boots is how you get a repeat job next year.

·       Old rubber feels hard as a hockey puck or pinholes when you flex it — that's your cue.

Will it fit my drive?

Check the drive tag — don't order off engine HP alone.

Brand	Model / Drive	Rated HP	Type	Years	Kit OEM set
MerCruiser	Alpha One Gen I	120–260	Sterndrive	1983–1990	78458A1+60932A4+74639A2
MerCruiser	R / MR (Gen I context)	Varies	Sterndrive	1983–1990	Same 3-bellow set
MerCruiser	S/N 06225577 thru 0D469858	120–260	Sterndrive	1983–1990	30-803097T1 kit
MerCruiser	4.3L / 5.0L / 5.7L on Gen I	120–260	Sterndrive	1983–1990	Verify S/N on drive tag

 

Wrong kit? We've all been close before — read this

·       NOT for Alpha One Gen II (1991+, S/N 0D469859 and up) — different boots entirely; grab GHMarine 18BK003 instead.

·       NOT for Bravo sterndrives — wrong family; see GHMarine 18B5001 / 17B3003.

·       NOT for the big transom overhaul with gimbal bearing + gasket kit 27-94996Q2 — that's 17B3005; this box is rubber only.

·       NOT for Gen II OEM kit 30-803099T1 — won't fit your Gen I drive even if the engine's the same size.

·       NOT for a single Gen II exhaust bellow 18654A1 / 8M0124227 — that's 17B1003, not this Gen I tube kit.

What actually ships

·       1 × exhaust tube / bellow (78458A1) with clamps

·       1 × U-joint bellow with ridge (60932A4) with clamps

·       1 × shift cable bellow (74639A2) with clamps

·       Not in the box: gimbal bearing, gasket kit 27-94996Q2, glue, expander 22ET001, driver 21B1001

Good product photos show three rubber boots — skip supplier shots labeled gimbal bearing kit or full transom hardware overhaul.

Just need one boot?

·       17B1015 — exhaust tube Gen I (78458A1)

·       17B1004 — ridge U-joint Gen I (60932A4)

·       17B1005 — shift only, one piece (74639A2)

·       Gen II three-bellow kit → 18BK003 (816431A1 + 18654A1 + 74639A2)

Guys usually add these to the cart

·       Bellows expander — 22ET001 (exhaust and shift ends are tight without it)

·       Sleeve install driver — 21B1001 (U-joint retainer step)

·       Marine bellows adhesive — sold separately, but you'll want it

Install order (the way most techs do it)

1. Shift boot first, then U-joint, then exhaust tube last — exhaust is the tight one; expander 22ET001 helps.

2. Glue both ends; let it tack up before you clamp.

3. U-joint retainer sleeve — driver 21B1001 per your manual.

4. Drive back on, muffs, run it, then check the bilge for water.

FAQ

What's actually in the box?

Three rubber boots — exhaust tube 78458A1, ridge U-joint 60932A4, shift 74639A2. Clamps on each. No gimbal bearing, no gasket kit, no glue, no tools. Just the rubber you'd swap with the drive off.

Why not just buy the three singles?

Honest answer: pulling the drive is the job nobody wants to do twice. Once it's off, peek at all three boots — they sit in the same hot, salty mess. One cracked or oily boot usually means the other two are on borrowed time. This kit gets you all three Gen I numbers in one shipment so you're not back under the boat next spring because you cheaped out on one boot.

Will this fit my Alpha One Gen I?

If your drive tag shows Gen I / R / MR / Alpha One and serial 06225577 through 0D469858 (1983–1990 is typical), yeah — this is your three-bellow set. Not Gen II (816431A1 family) and not Bravo. Don't guess from engine HP — read the drive serial.

Does this come with the gimbal bearing?

Nope — rubber only. No bearing, no 27-94996Q2 gasket kit, no hardware overhaul. Need that full rebuild story? That's a different SKU (17B3005). This is for owners who just need fresh transom rubber.

Gen I vs Gen II — how do I tell which kit I need?

Gen I (this kit) uses exhaust tube 78458A1 and ridge U-joint 60932A4. Gen II (1991+) uses exhaust bellow 18654A1 and accordion U-joint 816431A1 — that's kit 18BK003 / 30-803099T1. They look alike in photos; they're not interchangeable. Match drive serial, not how big your motor is.

Do I need glue and the expander tool?

For a job you'd be proud of, yeah — marine bellows adhesive, expander 22ET001 on the tight exhaust and shift ends, sleeve driver 21B1001 on the U-joint retainer step. None of that ships in this box.

Only one boot looks bad — do I still need the kit?

If the drive's already off and two boots look sketchy, get the kit. If it's truly just the exhaust tube leaking (super common), save money and grab 17B1015 alone. U-joint ridge boot only → 17B1004. Shift only → 17B1005.

Please note

Aftermarket replacement kit — not OEM packaging. Confirm Alpha One Gen I serial (06225577 thru 0D469858) before you order. Not affiliated with engine manufacturers referenced above.