OMC Sterndrive 140 HP convert to V6/V8

[sardonicus]

I just got a boat, based on the model number 990216S its a 73. Previous owner let water sit in it over winter and big shocker the block is cracked. We are going to try some ninja weld repair job on it but in the likely event that doesn't work. Can this motor be replaced with a V6 or a V8 motor? Preferably something that has some automotive counterparts so it wont be so hard to find parts for. The model number on this motor is W01421 just in case that is helpful for getting me the information I need.

If you have any suggestions on where I might look for a used block those are welcome too. I haven't torn into it yet just got the boat today but for now I am assuming that other everything else is fine.

 

[Howard Sterndrive]

Re: OMC Sterndrive 140 HP convert to V6/V8

I am assuming that other everything else is fine.

might want to do some evaluating of the drive, stringers, floor etc.

in my experience (I have picked up quite a few free boats for parts), sometimes the outdrive blows up mid season, or other mechanical failure, so the boat gets shoved in the back yard, then winter comes and no one thinks to winterize it...

drain all drive compartments to look at fluids and take an ice pick to the floor and stringers. hole saw under seat bases etc to check floatation foam

 

[sardonicus]

Re: OMC Sterndrive 140 HP convert to V6/V8

Aye there is a lot of work to be done, I'll have to rebuild a lot of the stuff on the boat that was left out to weather, I am just hoping to find some information on converting from the 4 cylinder to a bigger more common motor for ease of maintenance later.

 

[Bondo]

Re: OMC Sterndrive 140 HP convert to V6/V8

I am just hoping to find some information on converting from the 4 cylinder to a bigger more common motor for ease of maintenance later.

Ayuh,.... Unless yer changing Everything, from pulleys to prop, it Ain't gonna happen...

 

[Scott Danforth]

Re: OMC Sterndrive 140 HP convert to V6/V8

the OMC drive behind the 4 cylinder has a different gear set than the V6/V8's, so your best bet is to find another 4 cylinder assuming you really really really really are attached to the OMC drive and the boat.

assuming the boat is in great shape, you can find someone selling a complete OMC motor and drive to drop in.

or if you have to redo a lot of stringer rot, and transom rot, look for either a different boat ready to drop in the water or a different motor and drive if you are doing a restore

 

[southkogs]

Re: OMC Sterndrive 140 HP convert to V6/V8

... and if you have to go as far as to change EVERYTHING, I would suggest a very careful cost/benefit analysis before you buy the first bolt. Unless it's significantly cheaper not to, I would take the opportunity to find something else with a Merc or Volvo.

As much as I like what I have, I'm not sure I could justify a complete OMC re-power unless I found it CHEAP.

 

[sardonicus]

Re: OMC Sterndrive 140 HP convert to V6/V8

The drive appears to be fine, most of what needs replaced in the boat is plywood stuff, the steering stuff seems to be functioning properly, and it doesn't appear that there is any water in the oil or something else that would indicate more needs replaced than the block and the exaust manifold. Looks like I can get the manifold and a rebuild kit for this motor for approximately 500. Just need to find a block, someone told me that the blocks are repairable with a proper weld... but I'm not sure that I believe that.

 

[tvpierce]

Re: OMC Sterndrive 140 HP convert to V6/V8

FYI: the motor is a 153 ci Chevy. It was used in the Chevy II (later called the Nova)... it's a very common engine. The part that's not common on the 140hp is the dual Carter carbs. They are a bear to find parts for.

 

[Howard Sterndrive]

Re: OMC Sterndrive 140 HP convert to V6/V8

it's a very common engine. The part that's not common on the 140hp is the dual Carter carbs. They are a bear to find parts for.

the 140hp is a 181 cu in engine, not 153.
if you have a time machine dialed to 1965, the 153 was used in cars, but the 181 never was
the dual carbs were never used on the 140hp engine. The dual carbs were used on 110 and 120 hp omc motors until 1971

 

[Scott Danforth]

Re: OMC Sterndrive 140 HP convert to V6/V8

^+1

 

[sardonicus]

Re: OMC Sterndrive 140 HP convert to V6/V8

I'm not lucky enough to have one fall in my lap with a motor that was used in cars, that would just be too convenient. I have to give some serious thought as to how much i really want to invest in this boat, the person that was suppose to have the carb to go on this motor doesn't anymore, and they aren't cheap. I may still fix it but it will likely be a multi-year project.

 

[Howard Sterndrive]

Re: OMC Sterndrive 140 HP convert to V6/V8

and with those multi year deals, the risks are two-fold

1. interest is lost - priorities change
2. when you're 95% done, you stumble across the same year and model that has been boathouse kept it's whole life and maintained properly, in mint shape for less than you have into the project

the latter has happened to me- I was searching for some stupid part to finish the resto and bam- there's my boat fresh out of a time capsule, hanging in an upscale boathouse on a lift for peanuts....

 

[sardonicus]

Re: OMC Sterndrive 140 HP convert to V6/V8

That will probably be exactly how it goes. At the very least this boat will be a learning experience, I've worked on a lot of things but a boat isn't among them, it'll be fun.