OMC out MERC. in

[wrnutsdad]

Previously posted if OMC engine could be replaced with a Mercury engine ,or if entire drive unit could be exchanged . Thanks for all the input guys.
I guess we will now find the answer to that Question. I found a complete motor and stern drive in an old boat . Engine was stuck from sitting up but the oil was clean and inside of engine looked great..managed to get it to rotate by hand ,so I made him an offer (250.00)...doggone if he didnt take it !!!
Turns out engine had been replaced and only run for 2 seasons...out drive was serviced at the same time with new bearings and seals.
Im giving everyone a heads up !!! Im probably gonna be asking a LOT of questions . Ill keep making reg. post to let yall know how it is going ....
Now where is that shoehorn ????


1985 Reinken
140 hp OMC

 

[Bondo]

Re: OMC out MERC. in

I found a complete motor and stern drive in an old boat .

Ayuh,... What motor,..?? What drive,..?? What vintage,..??

 

[superbenk]

Re: OMC out MERC. in

Previously posted if OMC engine could be replaced with a Mercury engine ,or if entire drive unit could be exchanged . Thanks for all the input guys.

1985 Reinken
140 hp OMC

Ayuh,... What motor,..?? What drive,..?? What vintage,..??

Based on the opening, the year & the HP of the OMC, I'm going to guess a late model Stringer. If that's the case, I hope he's handy with fiberglass & carpentry

(Yes, I've considered many times the idea of replacing my Stringer with a Merc setup, but a newer boat would be nice too )

 

[wrnutsdad]

Re: OMC out MERC. in

Sorry Guys ,guess I was excited about my DEAL. Boat is 85 Reinken 16 ft. w/OMC 140 HP Gm 4cyl .Believe I got the 400 series drive unit .
The new engine is a 79 to 81 Merc. ( best I can tell ) 140 HP according to owner w/Mercruiser drive unit ( no clue which one ) the boat was a 77 Marquis trihull .
Now for the Bad news!!! Was wiping off the years of dust ,acorns ,leaves ,squirrel droppings , and found a decal on valve cover ENGINE IS A 120 HP UNIT !! Still may work as everything on both engines looks very similar.
Got it home ,pulled the plugs and put a pint of oil & brake fluid mix in each cyl. Let it sit all day and gently rotated back and forth untill I rotated it a full revolution . Let it sit again for a while , went back and now she's free ,no rough spots nice and smooth !!
Bad news #2... hooked up battery to spin out all the oil in cyl. and CLUNK.. solenoid throws out but starter wont spin. I know the engines free so its got to be the starter. Removed starter ( oh Yea that was a pain ! ) slam full of rust !!! End cap bushing is permanently mated to the starter armature shaft , must have sat in water a while . Hope this isnt signs of things to come !! OMC starter looks the same ,will let yall know how it works out.
Thanks !!!!

 

[wrnutsdad]

Re: OMC out MERC. in

Ok Guys the Journey continues !! Took the starter off the OMC ,,,Man, I just Thought the MERC, starter was a PAIN to get off!!! The OMC has very ,very little room to get to the bolts and there are wires running everywhere..only took an hour to remove the inboard bolt.
But now for the good news !! The starter bolted right up and the engine spins like a top !!! Hey this thing might work out after all !!! Went to check compression but low and behold my two compression gauges havent been used in so long (2o years or more) they were dry rotted and could not get a good seal( dont use them much in collision work ) will let everyone know what I find. If cylinders are Good Im gonna fire this thing up(after checking oil pressure).
Second thought... would it be possible to disconnect drive unit from engine to prevent damage to drive unit?? If not ,then what needs to be done to
ensure I dont TOAST a perfectly good unit ??
Thanks !!!

 

[bruceb58]

Re: OMC out MERC. in

So you are planning on doing fiberglass work on the transom of your OMC boat to put this Merc unit in? Or...are you just swapping engines and not the actual drives?

 

[wrnutsdad]

Re: OMC out MERC. in

Thanks Bruce for the question, at this point the plan is to just swap the engines as the OMC stern drive has less than 2 yrs running since being replaced . But if needed am willing to swap entire drive train . Supposedly the Merc. drive just had bearings and seals replaced 2 yrs before it was set up,with very little run time..
Actually know the OMC boats history. Neighbor and good friend bought a complete sterndrive 3 yrs ago , had someone go through it and installed it on the boat .Boat went in water one time and then he got sick. He passed away shortly afterwards...boat sat untill grandson took it to Tenn. Ran it one season ,spent 500.00 on having it tuned up and other stuff ( his words ) took it out this year and burnt the engine.Drug it back to Grandmas house. She called me and asked if I would like to have it. Boat appears to be very solid and worth saving .
What are your thoughts ??? Now is the time to determine which way to go ..
Thanks !!!

 

[bruceb58]

Re: OMC out MERC. in

Since the original boat is a Stringer drive putting the Merc drive on the original boat is really a waste of time because the hole is a lot bigger on the stringer boat. Swap engines if they are the identical engines. I am not familiar with the 2 engines so that info will have to come from someone else.

 

[wrnutsdad]

Re: OMC out MERC. in

Thanks Bruce,
That was my initial plan as the engines really look identical . It really is a shame the OMC is locked up as I found out that the boat was used very little during its life.Omc engine looks BRAND NEW inside and outside.Most of the damage to boat is all due to sitting up ,,seats bad ,wiring chewed up etc.
Anyone have any thoughts on disconnecting engine from drive unit before start up ? Really would like to hear it run BEFORE going through all the trouble of pulling it , and putting it in the Reinken. Or just put muffs on and go for it ???Sure would hate to mess up the merc drive unit. What needs to be done to a drive that has been sitting since 2001 before starting engine ???
Once again THANKS !!!!

 

[reavesga]

Re: OMC out MERC. in

If starting the motor connected to the mercury unit you will want to make sure to supply water to the lower unit so you don't burn up the water pump in the lower unit. Also check oil in the drive. Everything else should be fine.

If starting the OMC unit same deal, supply water to the lower unit.

Pulling the OMC stringer engine is a pain. You will have to remove the out drive. Then remove the bladder seal. Then pull the entire engine and intermediate housing out of the boat. Then remove the intermediate housing from the engine. Reverse all those steps using new parts where appropriate and you are back in business. Might do the ball gears while it is all apart. If you have the tru course steering you will have to remove that from the intermediate housing as well.

The 120hp and 140 hp GM 4 cylinders are identical except for the displacement which is done by different bores. Thats it.

As an option, you can pull the mercury outdrive off the back of the boat. 6 bolts and it slides right off. Now remove the water hose from the thermostat housing and attach it to a garden hose so that water is supplied to the engine. Prime the carb and fire it up. Engine should idle just fine spinning just the fly wheel.

Having kept an OMC stringer (1974 electric shift) and a Mercruiser alive. I would take the Merc. More parts, lower cost, techs know how to work on them. The OMC stringer, when it was running was great, but it is orphaned.

Just finished switching out my OMC for Merc in my Cuddy Cabin. If you are handy with fiberglass and wood, its not that hard to do.

 

[wrnutsdad]

Re: OMC out MERC. in

Thanks For the response.
Got some really good news !!! On starter only, the merc engine has 25 psi of oil pressure!!! Took compression test all cyls at 70 or above . One cyl over 100 during the dry test, shot in a alittle oil , spun engine and rechecked , all cylinders above 100 psi. I think there is a little rust on cyl. walls from sitting up ,which will leave after run in . Folks , things are looking good for this swap to happen!! Next step is to Fire it up !!! Think Ill take the advice and pull the Merc. sterndrive.Question ...Am I going to have a bunch of spining stuff to contend with ?? Also the 6 bolts reffered to ,are these the 3 vertical on lt & rt. side of drive ( mine are chrome )??? The remainder of the unit (intermediate drive ? ) going to be ok to run ?? Where is water pump actually located ?? Sorry so many questions ...been trying to find a good site for Merc. service manual download, but it seems that everyone has been shutdown.
THANKS GUYS !!!

 

[nola mike]

Re: OMC out MERC. in

Took compression test all cyls at 70 or above . One cyl over 100 during the dry test, shot in a alittle oil , spun engine and rechecked , all cylinders above 100 psi.

those are actually some pretty miserable compression numbers.

 

[reavesga]

Re: OMC out MERC. in

Those compression numbers are low. Should be 150 or so I would think. The drive will come off and there will be nothing spinning outside the boat. Just water running out. There are two water pumps. One in the lower unit to provide cooling to the engine. A second on the engine that circulates the water through the engine just like a car.

I got my mercruiser manuals off eBay for about $10.

 

[Bondo]

Re: OMC out MERC. in

Took compression test all cyls at 70 or above . One cyl over 100 during the dry test, shot in a alittle oil , spun engine and rechecked , all cylinders above 100 psi.

Ayuh,... you have a worn out rebuildable Core motor,....
Not a Runner...

 

[alilley]

Re: OMC out MERC. in

not trying to butt in on some one elses post here but this is somthing that i have been interested in as well. if you have an mercruiser motor that is shot and you find an omc that is good can you swap manifolds and all that over and swap motors out?? i am in kind of the same boat as the OP my 3.0mercruiser is shot (cracked getting water in the oil) and trying to figure out what my options are other then a new reman which are pricy

 

[wrnutsdad]

Re: OMC out MERC. in

Ok Guys , Heres My thinking .
The merc has set up for about eight years, was stuck when I first looked at it. I figure the rings are stuck,cylinder walls glazed from rust, rust on valve seats etc. any and all of these can lower a static compression test .
However, as I have witnessed many times ( Auto mechanic for years in a former life) all these problems will improve greatly just by running the engine ,particularly under a load. The engine can be fired on a hundred psi ,heck it will fire on 70 psi !! Thing is guys if I can get a couple seasons out of it , I think it will be worth it.
Dont get me wrong ... I really do appreciate your concerns and value your opinions. Now drop the drive, get a jug o gas, and fire it up !!! Oh ,yea water for cooling and extinguisher just in case !!!!
THANKS !!!

 

[reavesga]

Re: OMC out MERC. in

not trying to butt in on some one elses post here but this is somthing that i have been interested in as well. if you have an mercruiser motor that is shot and you find an omc that is good can you swap manifolds and all that over and swap motors out?? i am in kind of the same boat as the OP my 3.0mercruiser is shot (cracked getting water in the oil) and trying to figure out what my options are other then a new reman which are pricy

To the best of my knowledge the 3.0 blocks are all the same. You will find that OMC only as 4 bolts holding the transfer case to the motor where the Merc has 6. Turns out that OMC just plugs the holes with a threaded stud. When you put the drill to the plug it will just back out letting you bolt up the Merc bell housing. Also, the Merc design philosphy is studs on everything. OMC is bolts on everyting. You will have to move several of studs from the Merc block to the OMC block. Wiring harness, alternator, etc all will have to be moved as well. Not that tough to do though.

 

[reavesga]

Re: OMC out MERC. in

The engine can be fired on a hundred psi ,heck it will fire on 70 psi !! Thing is guys if I can get a couple seasons out of it , I think it will be worth it.
Dont get me wrong ... I really do appreciate your concerns and value your opinions. Now drop the drive, get a jug o gas, and fire it up !!! Oh ,yea water for cooling and extinguisher just in case !!!!
THANKS !!!

Let us know how it turns out. I have seen them come back to life for a while so you might be ok. Make sure you have the extinguisher just in case.

 

[wrnutsdad]

Re: OMC out MERC. in

IT LIVES !!!! (Sorta ),
Hey guys finally got a chance to work on the boat ...Pulled the drive ( Thanks Reeves) Cleaned & adjusted points,Hot wired Ignition ,sprayed some gas in carb and spun it over....It fired right up !!! Wooo !!WHoooo!! Decided to try to let it run for a few minutes on a jug of fuel ....so hooked everthing up ..took of the thermostat houseing .. pulled thermostat & put in the water hose for cooling. WATER WAS GOING EVERYWHERE !!!! The water was coming from the front welch plug( freeze) on the block ... completely gone !! Cant find it at all , not in the bilge ..not on the motor....water was also draining from the open petcock for draining the block .
Hoping that it was removed by someone for some reason ( yea its a long shot ... ok a really long shot ) I think ill buy a temp plug to go in the block and pressure check it. Will let yall know what I find ..

 

[HT32BSX115]

Re: OMC out MERC. in

The water was coming from the front welch plug( freeze) on the block

I know a LOT of people call them "Freeze-Plugs"..... (core-plugs)

A better description is probably "Freeze-Damage" plugs.....because they do not protect anything from freeze damage.......they usually indicate that it has already happened. (yes....I know they frequently "pop" out during freezing conditions in un-damaged blocks......but they are NOT responsible for "protecting" the block.....the block owners are just plain lucky in those instances!!!!)




Good luck!!


Rick