1970 181 to a 1978 181 different engine harness?

[Tapout2007]

I’ve got a issue with the engine harness connection, I had a 1970 181 140hp mercruiser and I got a 1978 mercruiser for free that was running and was going to swap it into my boat but the gimble and the engine harness plug is different and the gear shift and gimble are different, what did I get myself into?

 

[Tapout2007]

It is also a 140hp

 

[kenny nunez]

Do want to install the 78 model, or is the original 70 model transom plate in good condition?

 

[Tapout2007]

The 70 model transom plate is in condition, but the out drive is also getting replaced with the 78 alpha one out drive so would I also need to replace the transom plate? Also is there a good place to find the wiring schematics for both motors? So I can make sure the wires are going to what they are supposed to go?

 

[dubs283]

Gonna guess the 1970 model was equipped with an ammeter, hence the difference in harness plug.

Best bet for success is to use the entire 1978 package from pulley to prop including the power trim system. Would mean r and r of the entire transom assy but at least you know it'll work. Plus at this point you may as well considering the boat is most likely from 1970. Gives you a chance to clean and inspect the transom

Wiring diagrams are best found in the oem manuals. Either mercruiser #2 or #3 depending on serial number

 

[matt167]

I know 70 gimbal pins use nails. 78 might be screw in. That alone is worth the swap imo. 70 shifting is also on the transom. 78 might have the bracket on the valve cover.

I’m putting a complete 86 alpha one 3.0 assembly in place of a 1970 2.5

 

[Tapout2007]

Gonna guess the 1970 model was equipped with an ammeter, hence the difference in harness plug.

Best bet for success is to use the entire 1978 package from pulley to prop including the power trim system. Would mean r and r of the entire transom assy but at least you know it'll work. Plus at this point you may as well considering the boat is most likely from 1970. Gives you a chance to clean and inspect the transom

Wiring diagrams are best found in the oem manuals. Either mercruiser #2 or #3 depending on serial number

Where is the best place to find the manuals? Because I have searched on the internet but it only came up with parts places

 

[Tapout2007]

I know 70 gimbal pins use nails. 78 might be screw in. That alone is worth the swap imo. 70 shifting is also on the transom. 78 might have the bracket on the valve cover.

I’m putting a complete 86 alpha one 3.0 assembly in place of a 1970 2.5

Yes I want to replace the whole thing but will i need all new controls also?

 

[Tapout2007]

Where is the best place to find the manuals? Because I have searched on the internet but it only came up with parts places

Transom surprisingly is in great condition all very solid and no rotten areas

 

[matt167]

Yes I want to replace the whole thing but will i need all new controls also?

No. Controls are the same. You will need new cables as the length is slightly different

 

[Tapout2007]

No. Controls are the same. You will need new cables as the length is slightly different

Just the steering cable and throttle and gear shift cable? And where do you think I can find them? I have a 18’ StarCraft

 

[matt167]

Same as mine. I have a ‘71 offshore V 18.steering cable, you will probably need a new helm if the cable is no good. But steering will work the same. The control cables will be Gen 1 Mercury.

 

[kenny nunez]

If you want to keep it simple then swap the wire harness and alternator from the original engine to the later one.
If the drive shaft from the later drive is the same length then it will bolt right on. If there were no shifting problems with the older drive and the lower shift cable is free and smooth then you will save some time by leaving that alone. If the gimbal bearing and drive shaft bellows are good do the same.
Make sure the later drive is in good condition internally and replace the pump in it. Use the original front mount which will keep the alignment close and may not need any adjustment. If the mount bushings are good on either flywheel housing then use that one.
If something happens to the original gimbal housing then you still have a spare.
Good luck

 

[Tapout2007]

Same as mine. I have a ‘71 offshore V 18.steering cable, you will probably need a new helm if the cable is no good. But steering will work the same. The control cables will be Gen 1 Mercury.

Cable and steering move smoothly so just wondering if I could shorten the length somehow or just buy a new cable

If you want to keep it simple then swap the wire harness and alternator from the original engine to the later one.
If the drive shaft from the later drive is the same length then it will bolt right on. If there were no shifting problems with the older drive and the lower shift cable is free and smooth then you will save some time by leaving that alone. If the gimbal bearing and drive shaft bellows are good do the same.
Make sure the later drive is in good condition internally and replace the pump in it. Use the original front mount which will keep the alignment close and may not need any adjustment. If the mount bushings are good on either flywheel housing then use that one.
If something happens to the original gimbal housing then you still have a spare.
Good luck

Thanks for the advice I think that is what I’m going to try to do,

 

[matt167]

Steering cable for that old helm I don’t think exists. Cables can be found for the modern teleflex systems but that is pretty much it… but even if you go with the more modern transom assembly, the steering stays the same

In my case I bought it with a disassembled but complete drive. I didn’t know until much later that someone drilled the nails out and damaged the transom assembly doing so. I paid the same cost for a running and mechanically sound boat as the going rate for a transom assembly on eBay

 

[Tapout2007]

I’m trying to find the manual for a s/n 4649189 mercruiser 140, which is what I have, the wiring was easy to swap out. Found out the gimble bearing was bad so replacing that, would it be better to have everything mounted to the boat before I do that? Or can I do it without the motor being connected to the gimble housing?

 

[Scott06]

I’m trying to find the manual for a s/n 4649189 mercruiser 140, which is what I have, the wiring was easy to swap out. Found out the gimble bearing was bad so replacing that, would it be better to have everything mounted to the boat before I do that? Or can I do it without the motor being connected to the gimble housing?

You can instal the bearing without motor in the boat just can’t align the bearing to the coupler if it isn’t there

 

[Tapout2007]

So I can install it, and align it later when I get the motor in

 

[dubs283]

Best to r and r the gimbal bearing with the transom assy installed. You don't need the motor in place but in order to properly align the new bearing you need the motor set and a proper alignment tool

As far as manuals you need one, maybe two depending on serial numbers. Can't say which one for sure based on the s/n provided but 1970-78 most likely covers a range of manuals.

 

[Tapout2007]

Best to r and r the gimbal bearing with the transom assy installed. You don't need the motor in place but in order to properly align the new bearing you need the motor set and a proper alignment tool

As far as manuals you need one, maybe two depending on serial numbers. Can't say which one for sure based on the s/n provided but 1970-78 most likely covers a range of manuals.

Thank you for the info, I have been searching the web for manuals and the one I can find won’t download, I have tried for 2days now