Mercruiser 165 engine swap Help

"I just purchased a 74 Reinell

"I just purchased a 74 Reinell 19' with a Mercruiser 165. The guy who owned the boat left water in the engine during the winter causing the block and manifold to crack. I pulled the head,it is pitted and will need some machining and new valves. The price I got was $511.00 for the complete head work. Most of the parts for this year engine are NLA, so it really doesn't make sense to put any more $$$ or time into it. I can pick up a used 81 165 for a reasonable price, my question is will the 81 work without any issues or do I have any other options?"

The long block will be identic

The long block will be identical. compare the accessories to see if they are the same. It should be a direct swap.

"Hi raven wfo
My OMC 6cyl Blo

"Hi raven wfo
My OMC 6cyl Block is crack by the same way as yours. So I too had to look at my options.
You say you can pick up a used 1981 mercruiser?
No matter the Year of engine. Make very sure the internal parts are in good shape.
Unless You like pulling engines from Boats.
I will tell you what im doing and it might help you decide what you want to do.
First if you don't know yet we have the same block and internal engine parts. In fact the engine Block and head is a Chevy-GM-4.1L 250cid 6cyl engine. You could get one at many Salvage-Junk-Yards. What I did is ask people on EBay that where parting out a Merc-165hp if they would just sell me the Block. I got one for 75.00 Bucks. Junk Yard wanted $250.00 for a Chevy-GM Truck Block. My replacement block and some Engine parts from the old OMC-Engine will go to a machine shop. Others parts come from a Master Marine Rebuild Kit.
511.00 Bucks for the Head work is way to much $$$. Best to shop around. You can get a rebuilt head for 200.-300.00.
Whats the differance between Marine & Auto-Truck?
The Head you want Stainless steel Valves. Your old Merc head already has them.
In the Block You want a Marine CAM,Brass-Bronz freez plugs,Parts you get from a Marine Rebuild kit.
There is Web sites you can get ANY part for this engine. Even a brand New Mercruiser Block,Head,Manifold. Yep its not cheap. Might be cheaper from a Chevy Parts Dealer web site.
Just understand some parts are the same;some are not. Manifold is a Merc Not chevy.
And VERY IMPORTANT ALL PARTS USED IN ELECTRICAL & FUEL SYSTEM ARE MARINE. NOT AUTO. NEVER USE AUTO PARTS. If you do Ka-Boom.
And Yes I Know I dont Know everything,thats why I ask alot of qestions."

"Thanks for the info.If I pick

"Thanks for the info.If I pick up the 81 engine, will it bolt up to my existing outdrive, motor mounts, throttle controls and electrical or will I need to change this from my 74 engine? Thanks again."

"1981? If its the Mercruiser

"1981? If its the Mercruiser 165hp 4cyl
It's Not the same engine. What I mean is there is a Mercruiser 4cly 165hp engine,it also has a GM-Block. And I think it came out in the 80's And it will not work with your outdrive.
Well it might if you want to change some outdrive gears.
But wont work with the other parts.
You need a Murcruser 6cly 165hp. From 1970-1976. But if some one said they have a 1981 Merc 6cyl 165hp. And it is the same block & Head as your 1974.
It should bolt right up to your outdrive; Best to use the original wiring thats in the boat.
As for carb. Its a Newer carb,might need to use some parts from original boats linkage.
The point im making is 1970-1976 Chevy-GM used the same HEAD-NON-INTEGRAL-TYPE. Meaning the Intake-Exhaust is seprate. As is the Mercruiser engines & OMC engines of this type.
After 1976 Chevy came out with Heads that have the Intake&Exh as part of the head.
So if you have a Mercruiser 1981 the head has to be the old type chevy-GM 1970-1976.
Hope this helps Ya."

"Well I found out this morning

"Well I found out this morning the 81 engine is a 4cyl not a 6cyl. It looks like in the mean time, I will be doing some repairs to the 6cyl until I can possibly locate another one."

Hi raven wfo
If I was you I w

Hi raven wfo
If I was you I would keep looking on EBay & junk yards;not just for a Mercruiser 6cyl engine. But for a 1970-1976 Chevy 250 inline six engine.
Then you only have to repair your Mercruiser Manifold. And do a little work on a Chevy 250 engine to make it a Marine type.
If your able to pull the motor and put one in the boat. Then you can do the work to make a Chevy into a Marine engine. Its not that hard.

"I currently have a mercruiser

"I currently have a mercruiser 488 6 cyl. I'm considering dropping a fresh built up chevy 350 out of a truck in it's place. Aside from exhause and cooling, would the engine itself bolt up to the bellhousing? If not would a different bellhouseing for a v8 mean that I would need a different transom mounting plate at the rear of the engine? Would gear ratios in the transmission be a problem since the outdrives typically have different ratios depending on if they're v8's or 6's"