OMC or Yamaha

[Eres04]

I know both sterndrive engines are discontinued but what would I be better off with?

 

[Alumarine]

I know both sterndrive engines are discontinued but what would I be better off with?

Neither is the answer but if for some strange reason you had to pick one then OMC.

 

[Lou C]

You can find most OMC parts, Yamaha sterndrive parts are extremely rare. That said it depends on what OMC you are talking about...
Stringers, no one around here will work on them, parts can be found (used from fresh water areas) but they are all so old
Cobras, much easier to find common parts, but avoid:
The cone clutch King Cobra, hard to find parts
The later models with Ford fuel injected engines
Those with Splitfire ignition

The easiest ones are the GM, carbed engines, best would be the '94 and newer Joint Venture drive which is the same as a Volvo SX.

 

[Eres04]

Neither is the answer but if for some strange reason you had to pick one then OMC.

I currently own a 92 chaparral with a 7.4 Yamaha I/O. I haven’t had a problem with it yet and just done it’s anual service but want to move on from it so I do t have to deal with a part issue later. Just there’s some Four WINNS that have popped up at fair value that have 5.0 cobras on them so just curious.

 

[briangcc]

'05 and newer Four Winns are wood free. Gets you to Merc or Volvo power. Might want to up the budget a touch.

 

[Lou C]

I currently own a 92 chaparral with a 7.4 Yamaha I/O. I haven’t had a problem with it yet and just done it’s anual service but want to move on from it so I do t have to deal with a part issue later. Just there’s some Four WINNS that have popped up at fair value that have 5.0 cobras on them so just curious.

It really depends on what year and model
for example:
the best would be a '94 and newer with the joint venture drive (really the same as a Volvo) and a GM carburated engine.
The Ford engines aren't bad if carbureted but the EFI parts and some ignition parts can't be found. So you could wind up with a Ford EFI system that when it breaks, can't be fixed, then you'd have to convert it back to a 4bbl carb, and maybe have to change the distributor as well. A deal breaker? Well not for me, because I can source the parts, & do the work, but if you don't do your own work, that is a deal breaker.
Honestly I had good luck in fact VERY good luck with my 1988 4.3-4bbl Cobra. Used in salt water 100% it has really held up well.
But I have a garage full of OMC spares, and an OMC shop manual and I know how to do the tricky OMC dog clutch shift cable adjustment myself.
Many boat repair places will not work on the stringers and many won't work on the dog clutch Cobras either. You can't just go to the local marine shop and buy OMC parts, you have to look around, sometimes the best you can find is used freshwater parts.

Wanna make your life easy? Go a few years newer, go with a GM carbureted engine with a Mercruiser Alpha drive. Parts are everywhere, and any mechanic can work on it.

 

[Scott Danforth]

I know both sterndrive engines are discontinued but what would I be better off with?

If you want to use it as. An anchor, the Yamaha weighs a bit more

If you want to use it as wall art. The OMC may look better

If you want to use them on a boat..... Neither.

Since your boat has a Yamaha. I would look for a complete Bravo setup with a bad motor.

However the Gen V motor is the least desirable big block

 

[dubs283]

However the Gen V motor is the least desirable big block

I understand the latest production Gen VI/L29 454/7.4L is the most desirable for torque/hp but what advantages does a Gen IV (1970-1990) have over a Gen V (1991-1995)?

Gonna guess beefier casting? More durable/heat tolerable heads/combustion chambers?

 

[Scott Danforth]

I understand the latest production Gen VI/L29 454/7.4L is the most desirable for torque/hp but what advantages does a Gen IV (1970-1990) have over a Gen V (1991-1995)?

Gonna guess beefier casting? More durable/heat tolerable heads/combustion chambers?

Gen VI has Slightly better block webbing then the Gen V

Priority mains oiling is updated

Roller motor vs flat tappet

Forged crank vs crank

Better heads (the Gen V had peanut ports). The stock L29 heads have a vortec like combustion chamber

Back to the Mark IV style of head gasket eliminating the Gen V only heads


Regarding the 70-90 Mark IV block.....it is a 2-piece RMS block with flat tappet cam. Some have thicker cylinder walls, however you have to be careful of core shift.

Other than it's been around as a platform for many years, there aren't many advantages of the older block. The later Gen VI motors have more advantages

 

[dubs283]

Good info, thanks