It’s been a while since I posted anything about this boat – but then again, it’s been a while since I did anything with it either.
As I mentioned in my last couple of posts, I discovered that the engine had an internal crack, and water was getting into the oil. With other priorities in life, I just decided to put the boat in the garage at my in-laws cottage after I pulled the engine out, and just kept my eyes open for a suitable engine, at a suitable price.
I did get some work done on my bigger boat last summer, and through this spring and summer so far, but I still have a LOT to do on it.
Anyway, a couple of weeks ago I came across a Mercruiser 140 engine listed online for a reasonable price, and coincidentally had almost the same amount of extra cash on hand from a side job I had done, so I went to look at the engine.
So… my original engine was an older version (unknown vintage/origin) Mercuiser 120, Rochester 2-Jet carb, mated to an Alpha 1/Gen 1 transom bracket and gimbal housing, with an MR drive on it.
The engine I ended up getting (the guy had two to choose from), was 140 from a newer drive and had rear mounts and exhaust riser that wouldn’t match the existing setup in my boat. He did have an older 140 that would have been a drop-in, but showed evidence of previous crack repairs in the water jacket. The engine I bought looked solid, no evidence of damage of any kind. It started and ran on his shop floor – although we didn’t run it for long with no water supply, and indoors… I knew that all of the 120 and 140 Mercruisers are based on the same basic block, and since I had a complete running engine at home (with a cracked block), I figured there would be no reason I couldn’t make it work somehow!
So – I brought the engine home, set the two engines side by side in the garage, and started working on making the new engine fit where the old engine had been.
New engine on the left, old one on the right...
First, I removed the exhaust risers. They weren’t interchangeable – the mounting hole spacing and water jacket holes were all different dimensions.
So, I decided to tackle the rear mounts that are part of the bell housing/flywheel cover. The coupler was also different. So was the flywheel. So I removed all of those from both engines, and swapped the flywheel mounting studs from the old engine to the new engine (the crankshaft holes were the same). Installed the flywheel, coupler, and cover with mounts. That was fairly straightforward.
Back to the riser problem…
The manifold on the old engine was fine. The exhaust riser was new. The carb had been rebuilt. So, I figured I would just swap the whole manifold. I unbolted both manifolds, and discovered that although the bolt hole spacing is identical, the 140 had larger exhaust ports that the old 120 manifold wouldn’t cover. Great.
So, the only thing to do was swap the whole head. Ordered a new head gasket for a 140 (3 litre) Mercruiser, and the 120 head bolted on no problem. Installed the manifold and carb from the 120. No problem. The engine would now fit in my boat.
This is what oil looks like with water mixed in...
I also swapped in the ignition from the 120 (I had upgraded to Pertronix), and also installed the new alternator I had put on the 120.
Then I discovered another issue – the 140 came from a boat with power steering, and had a thicker pulley on the water pump with two extra grooves. That pulley was going to interfere with the different cooling hose routing from the 120. So, I had to swap the water pump as well (the pulleys between the pumps weren’t interchangeable).
Anyway – it all eventually fit together, I got the engine in the boat, and as of this past Sunday it is in the water and running just fine. And the oil is staying clean!
This was my view last night when out for a cruise with my wife.
