well thanks to this board I went ahead and bought a used/rebuilt 1974 3.0 140 mercruiser to put in my 89 Wellcraft which had I believe a cracked block. the 74 engine had been rebuilt a year ago and looked in good shape but the hull was damaged so I got the engine cheap, the swap was Very simple and took just the afternoon.
first I pulled my original engine and Wow I was shocked it took about 30 minutes and it was out! 4 bolts and the battery terminals pretty much summed it up! I did not remove the outdrive! I had plenty of room.
next I set it by my new engine and here is what had to be swapped. I pulled the complete wire harness from the original engine and put it on the replacement, Including Starter, coil, alterator etc...I did this to save time and to keep the newer components. not to mention I left them hooked to the harnes so no chance of getting wires messed up!
next had to swap the valve cover since the throttle links mounted to my cover.
I swapped the manifold because I liked the original carb condition better and the carbs ARE NOT interchangable! but the manifolds are! Also to use the 74 manifold I would need the complete exhaust since it would not line up with the 89.
lastly i swapped the motor mounts. the front does not need to be changed but I swapped the front so my alignment would not be out. the rear mount is a must, the 74 bolt holes will not fit the 89 transom. all in all i spent about 2 hrs looking and swapping parts and another hour to maybe 1.5 hr to install the engine in the boat, it took twice as long to install then it did to remove which I expected!
it fired right up and runs great! unfortunalty the first run to the lake was unsuccesfull! it started to over heat and I found the impeller was bad, ran great on the hose and muffs but but not in the lake! so another 2 hrs spent on Sunday replacing the impeller and it's ready to go! this time I cut a 55gallon barrell in half and tested in water!~!!~
i had seen other posts on this type of a change out and guys had issues with wiring, I am not sure why anyone would not swap out the complete engine harness since it takes less then 30 minutes to swap the whole engine electrical! on my 89 engine the rear bracket mounts the circuit breaker, starter solinoid and harness plug, so 2 bolts removes this bracket and 1/2 the electrical! the starter didn't need to be swapped but mine was damaged in transport so I swapped them, and the alternator, had about 5 wires and it was easy to remove the one bolt holding it on and leave the harness attached
first I pulled my original engine and Wow I was shocked it took about 30 minutes and it was out! 4 bolts and the battery terminals pretty much summed it up! I did not remove the outdrive! I had plenty of room.
next I set it by my new engine and here is what had to be swapped. I pulled the complete wire harness from the original engine and put it on the replacement, Including Starter, coil, alterator etc...I did this to save time and to keep the newer components. not to mention I left them hooked to the harnes so no chance of getting wires messed up!
next had to swap the valve cover since the throttle links mounted to my cover.
I swapped the manifold because I liked the original carb condition better and the carbs ARE NOT interchangable! but the manifolds are! Also to use the 74 manifold I would need the complete exhaust since it would not line up with the 89.
lastly i swapped the motor mounts. the front does not need to be changed but I swapped the front so my alignment would not be out. the rear mount is a must, the 74 bolt holes will not fit the 89 transom. all in all i spent about 2 hrs looking and swapping parts and another hour to maybe 1.5 hr to install the engine in the boat, it took twice as long to install then it did to remove which I expected!
it fired right up and runs great! unfortunalty the first run to the lake was unsuccesfull! it started to over heat and I found the impeller was bad, ran great on the hose and muffs but but not in the lake! so another 2 hrs spent on Sunday replacing the impeller and it's ready to go! this time I cut a 55gallon barrell in half and tested in water!~!!~
i had seen other posts on this type of a change out and guys had issues with wiring, I am not sure why anyone would not swap out the complete engine harness since it takes less then 30 minutes to swap the whole engine electrical! on my 89 engine the rear bracket mounts the circuit breaker, starter solinoid and harness plug, so 2 bolts removes this bracket and 1/2 the electrical! the starter didn't need to be swapped but mine was damaged in transport so I swapped them, and the alternator, had about 5 wires and it was easy to remove the one bolt holding it on and leave the harness attached