351W Engine Swap

[Twainer]

I might attempt to do this myself. Can anyone out there tell me how difficult of a job this is? I have an 18' 1978 Mark Twain OMC Bowrider with a 77' 351W engine. The interior is already out being re-done so that won't get in my way but concerned with pulling it apart from the drive unit & mating it back up. I have done car motors before but know little to nothing about marine applications.
Before I do any of that I also want to make sure there is nothing that can be done to save this block like hone the one cylinder with corrosion?

 

[southkogs]

I would think yankin' a stringer is pretty easy, but I've never done it. Do you know if it's electric shift ('77), or hydro-mechanical ('78)? That'll matter to how you disconnect the drive from the intermediate. Once the drive is off, and the boot is off, you should be able to get the rest of it together.

Do you have select trim on it?

 

[Twainer]

I would think yankin' a stringer is pretty easy, but I've never done it. Do you know if it's electric shift ('77), or hydro-mechanical ('78)? That'll matter to how you disconnect the drive from the intermediate. Once the drive is off, and the boot is off, you should be able to get the rest of it together.

Do you have select trim on it?

Sorry I can't answer any of that. First boat so I am really ignorant with it all. I am mechanically inclined but just have never worked on boats, only auto's. As I am looking for engines, how do I find out if I have standard or reverse rotation. Does that only come into play when you have duel engines?

 

[southkogs]

Not sure. I've never had duals. I would assume that the counter rotation is handled in the stern drive, but I'm not sure.

Take a few photos of the front of the engine and then shoot a couple of the drive.

 

[Bondo]

how do I find out if I have standard or reverse rotation.

Ayuh,.... I gotta believe it's standard left-hand rotation,......

Sterndrives use standard motors, 'n counter-rotate the prop shaft,....

I'll clarify, 'n give myself an escape route by sayin',.... I've never seen a counter rotatin' sterndrive Motor,...

 

[Twainer]

I would think yankin' a stringer is pretty easy, but I've never done it. Do you know if it's electric shift ('77), or hydro-mechanical ('78)? That'll matter to how you disconnect the drive from the intermediate. Once the drive is off, and the boot is off, you should be able to get the rest of it together.

Do you have select trim on it?

I am going to see over the next few days (weather permitting) if I can get you some photos of what you are asking for. From everything that I have gathered off of posts & u-tube videos this is not that hard of a job. I have yanked auto engines out & this looks fairly easy. I guess when I yanked out the straight 6 out of our old 63' chevy that was really easy but compared to Fwd & newer autos this looks like something I can make happen. I don't think I would want to try it at my house like some I have seen but I have access to our shop with forklifts so I am thinking possibly doing this over the long 4th weekend.
I've seen where several guys pulled their motors out (or wish they did) with the outdrive left in. They just stressed that you need to have something under it to support it while you do the swap.
I think my biggest hurdle is going to be getting the new motor tuned & running. It has been a long time since I have timed a motor, adjusted a 4bbl. carb, & adjusted valves. The previous mechanic changed it over to elec. ignition so I won't have to screw with points.
I think with everybody on here & other forums I can pull this off. Gotta love the wealth of info here on the internet!

 

[southkogs]

Don't leave the drive on. The Stringer doesn't connect to the transom like a Merc, Cobra or Volvo ... it passes through the transom. You'll need the stern drive off from the pivot points back. How you do that is a little different between a '77 or a '78, but either way it's gotta' come off before you pull the motor.

 

[Twainer]

Now you guys have me all confused on what to expect?

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1. [h=2]
   
   Re: Pulling my 1977 omc 351w out of my boat[/h]
   Hey chief, I left the bell housing in.....it just seems more easier that way,I did pull the out drive,but really it does not appear I had too.........if I have to ever pull the engine again god forbid would it have been possible to leave the outdrive in and just make sure the splines are lined up right when attaching the engine and lining it up when I drop the engine back in? I know on autos I have had to leave the transmission in and just made sure the clutch plate was lined up so it wouls slid right in.........I used a flat bed trailer to set the cherry picker on for the height to remove the engine becuz the boat was to high,but it worked out good,I thoght about taking the tires off the boat trailer to give it some more clearance but a friend of mine loaned me his trailer to ste the trailer on​
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• 03-25-2011, 08:56 PM #10
  
  chiefalen
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1. [h=2]
   
   Re: Pulling my 1977 omc 351w out of my boat[/h]
   There is no need to remove the drive on a stringer boat.
   
   Just place some flat wood under the skeg of the drive fully down and crank the bow up till the skeg sits on the wood. See this stops the drive from dropping when you remove the motor, and iit takes the stess off the coupler.
   
   Thats how i removed my motor left the bell housing in place.
   
   There must be 6-8 inch's in front of the motor to move it forward so the splines come out of the coupler.​
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[southkogs]

A "stringer" doesn't attach to the transom. It attaches to the motor, which is mounted to the boat's stringers (hence the name). I can understand not disconnecting the bell housing, the intermediate is pretty much inside the boat. But I have no idea what would hold the drive up if you left it "on the boat" because the engine that's holding it right now would be gone. Setting it on a block of wood would be just a way to lean it against the hull.

Pulling the drive through the transom hole might be possible (I've never considered it). Measure your cavitation plate and see if it'll fit through the hole. But personally, if you're pulling the motor, I'd just disconnect the drive altogether. Most of the work will be done already just 'cuz the motor is gonna' be gone.

 

[Twainer]

Thanks a bunch for the reply! I have to leave town for the weekend but when I get back I am going to try & get some photos posted up to show what I am up against

 

[Twainer]

No Title

Getting close now. Does the motor not just hook up to a shaft like on the transmission on a vehicle? I have included some pics... will support under the outdrive on the outside of the boat plus the mounts included in the pics be enough to hold it while I do the engine swap? I have also included a picture of a set screw that is on both motor mounts. What are these for motor alignment?

 

[Twainer]

I forgot to ask in my last post. I am getting ready to order my engine from "marineengines4less". Most everything I have read has been positive reviews. Has anyone on here had any problem with them?

 

[southkogs]

Does the motor not just hook up to a shaft like on the transmission on a vehicle? ... will support under the outdrive on the outside of the boat plus the mounts included in the pics be enough to hold it while I do the engine swap?

Connection between the drive and the Intermediate happens at the ball gears. It's not a continuous shaft.

I don't know if the drive is gonna' hold that way. For the few minutes it takes to pull it off, I can't imagine why you wouldn't.

 

[VE8EV]

The rear mounts will probably keep the intermediate from falling out the back if you do it that way -but- it's so easy to just pull the whole thing and work on it out of the boat. Yank the drive off, two plugs to undo for the electrical, undo the throttle cable and fuel line, take off the transom boot, pull the lag screws on the mounts and the whole thing comes right out in one piece. I pulled two stringers this month for spares, the first one took about a half hour and the second one about 15 minutes.

 

[VE8EV]

I see yours has TruCourse steering so add another 5 minutes to undo the steering cable.

The little set screw on the mounts appears to just keep the engine torque from bending the bolts since it has such different geometry than an automotive setup.

 

[Twainer]

Thanks all for the replies. Sounds easy enough to just yank the whole thing. Engine should be here in a couple of weeks. Wish me luck!