How to Select The Right Sterndrive for Your Boat

 

When it comes to your sterndrive ( also known as an outdrive ), it is good practice to inspect and service it annually, that way you can be on the lookout for any possible issues that may arise, and get them fixed before a catastrophic event requires expensive repairs or replacements.

 

A couple of things to look for are water intrusion caused by either a bad seal or a bad drain vent / drain plug gasket failure. The color of the oil will be a milky or chocolate colored when water is present. The other thing to look for is metal or fine metallic shavings in the oil, which are from signs of wear to the bearings and gears. If there is an excessive amount, then it may be time to consider having the sterndrive looked at by a certified marine mechanic so as to determine if it is cost effective to have it repaired or just replaced.

 

 

When replacing your sterndrive, you will want to make sure you are purchasing the correct one. Make sure that the gear ratio and the rotation match what your engine manufacturer recommends. There are several different gear ratios available which depend on engine horsepower and displacement.

 

When ordering a sterndrive, it is also advised to have your engine serial number or model number available when contacting us. This will help with identifying the correct model type or year. MerCruiser stamps their serial number in the decal on the upper gear box next to the gear ratio. If it is not visible, and you are not sure which gear ratio to purchase, you can remove the cap that is held down by 4 bolts on the upper gear box and count the number of teeth that are on each of the two gears inside. Below are charts available that convert the number of teeth into the correct gear ratio.

 

Mercruiser R-Style Sterndrives (1969 – 1983)

Engine	HP	Liters/CID	Cylinders	Gear Ratio	Tooth Count	Year
2.5 Liter	120	2.5/153	4	1.98	20-24	1969-1983
2.5 Liter	130	2.5/153	4	1.98	20-24	1969-1983
165	165	3.7/224	6	1.65	24-24	1969-1983
470	170 – 190	4.3/262	4	1.84	17-19	1969-1983
215 – 233	205 – 230	351	8	1.5	20-22	1969-1983
260	260	5.7/350	8	1.5	20-22	1969-1983

Mercruiser Alpha 1 (1984 – 1990 Models)

Engine	HP	Liters/CID	Cylinders	Gear Ratio	Tooth Count	Year
2.5 Liter	120	2.5/153	4	1.98	20-24	1984-1990
3 Liter	130	3.0/181	4	1.98	20-24	1984-1990
165	165	3.7/224	4	1.84	17-19	1984-1990
175	175	4.3/262	6	1.84	17-19	1984-1990
180, 190, 470	180	3.7/224	4	1.84	17-19	1984-1990
200	200	5.0/305	8	1.65	24-24	1984-1990
205	205	4.3/262	6	1.84	17-19	1984-1990
230	230	5.0/305	8	1.5	20-22	1984-1990
260	260	5.7/350	8	1.5	20-22	1984-1990
350 Magnum	270	5.7/350	8	1.5	20-22	1984-1990

Mercruiser Alpha 1 Gen 2 (1991 & Newer)

Engine	HP	Liters/CID	Cylinders	Gear Ratio	Tooth Count	Year
3 Liter	130	3.0/181	4	2.0	24-24	1998-2005
3 Liter	130	3.0/181	4	1.94	20-24	1991-2005
4.3 Liter	175	4.3/262	6	1.81	17-19	1991-2005
5.0 Liter	230	5.0/305	8	1.61	24-24	1991-2005
5.7 Liter	260	5.7/350	8	1.47	20-22	1991-2005