1980 Center Console repower

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InvisiBill

New member
I've decided to repower my dad's 1980 V-20 Center Console. I may sell it later, but for now, the goal is to repower and use this summer.

Anything I should look out for, or be careful of? Anything you wish you had done during a new engine mounting? The boat has always been stored indoors, on a trailer. Mostly freshwater use, but a little salt water.

I've purchased a used 2020 Mercury 200hp, V6, with rigging. Sitting on an engine stand right now. I'm hoping to get it mounted to the transom next week.

I've removed the 1980 V6. My dad always claimed it was a 200hp with a 150hp cowling. I've never been able to find any info on the block. The engine ran 2 years ago on the trailer and hose. A little rough, but worked. Anyone interested in it?

(I tried uploading a few photos, but I got server errors. I'll try again later.)
 
What is the weight difference in the 2 motors? Make sure the shafts are the same. Transom in good shape?

If all that is good,sounds like a great plan.
 
I have the original engine off, but haven't weighed it yet. My limited research says 350 pounds. New motor's tag says 484 pounds. Transom appears to be in good shape. My dad put on an aluminum plate vertically along the transom (inside and outside), along with a piece of 1.5 inch thick teak across the top when he got the boat to support the engine.

Aluminum plate had a very minor amount of corrosion. We cleaned it up, then prime and painted it.


Shafts are the same, both 25 inch XL.

Old engine coming off:


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Newly painted aluminum paint installed on the transom

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Engine bolts are tight to help the silicone sealant around the edges seal.

New to us engine is mounted.
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Issues: original mounting bolts are in good shape, but the wrong lengths. One pair is 8 inches, the other is 4.5 inches. This 2020 model engine seems to need 5 or 5.5 inch bolts. I've ordered new ones, and should have them next week. Also, we put the engine on the wrong mounting holes, we'll need to come down 1 or 2 holes. But the wood on the transom will need to be chipped out if we go 2 holes down.
 
I would think the bolt pattern would be the same. I went from a 83 to a 94 to a 2015 using the same holes.

It looks like the wood strip on the transom was added to raise the older motor. Should be able to remove it.
 
Yes, the wood strip was added to keep more water out of the splash well when slowing down. Bolt pattern is the same, but the lengths are different. The 1980 Mercury uses 2 8 inch bolts and 2 4.5 inch ones. The frame for the bolts is much thicker at the top, and thin at the bottom. Newer engine is more uniform top to bottom. The nuts can grab the threads on the 4.5 inch bolt, but they don't get all of the threads.

Old engine weighs 404 pounds on a scale. So not as much of a weight difference as I was expecting.
 
Motor looks fantastic! by any chance did you use a transom support plate on the inside top bolts? It will help provide support if the previous bolts and washers were starting to indent into the fiberglass.
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ctmv20 said:
Motor looks fantastic! by any chance did you use a transom support plate on the inside top bolts? It will help provide support if the previous bolts and washers were starting to indent into the fiberglass.
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No, I haven’t. I can get one made pretty easily. But we do have a thinner, but full transom width sheet of aluminum back there. I think it’s all 5052 alloy. Not anodized. But almost zero corrosion either. I’ll take a photo tomorrow.

On the outside of the transom, under the now painted piece of aluminum, I did notice the fiber glass was indented a bit. Enough to be visible to the eye. Maybe 1/16 inch? I’m not sure what could be done about that, if the aluminum plate has been there for 45 years.
 
I took a second look at the splash well interior transom plate. I think it's more than thick enough, probably 0.100 aluminum all the way across.

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Not going to get much done with the engine the next day or two. Hopefully on Wednesday, we'll remove the new engine, knock some of the wood down a 1/4 inch or so, then re-mount the new engine 1 or 2 bolt holes lower.
 
What battery set up are people using on the V-20s? Originally, this boat has the battery on the starboard side of the bilge, under the splash well. One battery, and very hard to replace. I've built a new platform to go in the wells behind the center console, with space for two larger batteries.

Not bolted down yet, but this sizing check passed. We were able to get the deck plate on top without hitting the battery. We have space for two batteries to drop in, one port, one starboard, for easy replacement. I'll end up using a battery tray with straps to hold everything down, but we need to mount the platform to the stringers before that.

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