Engine coupler

[Baylinerchuck]

Can anyone tell me the difference between an 18643A5 coupler, and the 18643A8 coupler? Serial number for the 350 magnum is D808410 which leads me to the A8. Many sites show this as discontinued. The A5 seems to cover the year this engine was built. Is the A5 just an updated design or material?

 

[alldodge]

The letter and number after the part number (A5, A8) are manufacture identifiers (who made the part), and can also be the difference between Mercury and Quick silver. So don't give it much thought

 

[muc]

The letter and number after the part number (A5, A8) are manufacture identifiers (who made the part), and can also be the difference between Mercury and Quick silver. So don't give it much thought

This could be some very bad advice!

For this engine 0D808410

18643A7 is the coupler you should use, this p/n was 18643A2 and then 18643A4 before it's latest number.


If your serial number was above 0F000001 you would use 18643A5
If you had a Bravo the coupler number is 18311A17

18643A8 was used on jack shaft engines with a one piece rear main seal and is NLA

I'm pretty sure these are all different parts, I don't think MerCruiser would stock the same part under multiple numbers.

The difference between Quicksilver and Mercury Precision Parts is Q is used for Quicksilver instead of A

 

[alldodge]

Well I either have misunderstood Fun Times or this part number is a one off rare thing.

Yes, I do know about the Q, but just didn't feel the need to go any further.

 

[Baylinerchuck]

muc AllDodge When I look up the engine serial number under a few different part suppliers I get the 18643A8 part number as the coupler I need. Most places show this as no longer available, which to me seems absurd coming from Mercruiser, as they do not provide an alternative. The 18643A7 is the coupler plus the driveshaft from what I can tell, but I don’t see this listed as the part for this engine under any resource. The outdrive is an Alpha I Gen II.

Is there a significant difference in the A8 coupler that I need to use the A7 which requires a different driveshaft which Mercruiser includes? Inquiring minds. Thanks for the help guys.

 

[alldodge]

I would suggest following MUC's comment

 

[muc]

Baylinerchuck where are you finding the A8 coupler listed. Is it in the driveshaft extension section? You should be looking in the flywheel and crankshaft section.

The A7 coupler is kit that includes a yoke (what you call a driveshaft) and a A5 coupler. The only difference between the yoke that is on your drive now and the yoke that comes with the A7 coupler is an extra o ring groove.

So so you can use just a A5 coupler. But you won’t get the benefit of that 3rd o ring to help keep the grease in.

 

[Baylinerchuck]

muc , you are correct. I was looking at the wrong section. Thank you for the explanation on the why the assembly comes with the yoke. Very informative.