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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11052
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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I have a marine engine that i think is standard rotational.

Customer Question

i have a marine engine that i think is standard rotational. however it has gears for the timing. so the cam and oil pump run backwards. how do i fix it
JA: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.
Customer: the engine is a 7.4, 454 generation v.
JA: Is there anything else the Marine Mechanic should be aware of?
Customer: did u get the message of my problem
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.

Hello. My name is Tan.

If you have gears and not a chain the engine is an opposite rotation RH.

Could I get the make, model and serial number of your engine please?

Can you give me some history on what is going on that you are trying to fix please?

Customer: replied 1 year ago.
The motor in a 1990 model bay liner quit. so the last owner ordered a new motor. the motor came as a crate motor with the block and heads. the other parts were tone transferred. the previous owner did not fix transfer the engine. now i have the boat and motor and want to make it go. the old motor was a mercrusier gen iv 7.4 454. the new motor is a gen v. there are differences but i think most can be worked out. the issue at hand is the fact of the rotor and oil pump turning the wrong way. i do believe the crank is standard rotational because when at TDC when u turn it a little farther the exhaust valve opens.
Customer: replied 1 year ago.
The motor serial numbers do not match up to any i have checked. the block cast numbers say it is a 1993 gen v
Expert:  Tan replied 1 year ago.

Which way is the rotor turning? There is no difference in the crank on standard or opposite rotation. They just turn the crank in the opposite direction. A standard rotation motor is left hand from the back of the motor. To change the rotation the put gears for opposite rotation and a chain with gears for standard rotation.

If this is a sterndrive boat it has to be a standard rotation LH. So when you say gears that tells me wrong rotation.

Here is standard rotation timing gears and chain. Is this what you have?

Customer: replied 1 year ago.
no. the gears are meshing. the crank and the cam gear touch.
Customer: replied 1 year ago.
i am trying to send u a picture of gear configuration
Expert:  Tan replied 1 year ago.

Then that is an opposite rotation motor. It will only work if you change the gears to chain. The reason the rotor is turning wrong is the starter is turning this engine in the wrong direction. Is the rotor turning CCW counter clockwise? If yes you must change the timing gears.

Is this what you have?

Here is what you need for your engine.

Customer: replied 1 year ago.
this is my first time trying the computer communication on just answer. i do not want to continue and would like to make sure this is canceled. i think there is to many variables to discuss and come up with a answer. thank u for your time
Expert:  Tan replied 1 year ago.

No there isn't any variables you have the wrong timing set on the front of the engine this is all it can be causing the wrong rotation of the rotor. It is very simple some one ordered the wrong engine. I have been doing this for 40+ years. So it is an easy issue to resolve. This is probably why some one couldn't get the engine running they were turning an opposite rotation engine in the wrong direction. Change to chain and your issue is resolved.

Expert:  Tan replied 1 year ago.

I have nothing to do with billing I just answer questions. Contact customer service to cancel.