1968 Mercruiser 120 Engine

[WaterLauger]

My brother has a Mercruiser 120 and he left the water in it over the winter. He is looking at motor alternatives as his boat was underpowered. What engines bolt up to this outdrive?

 

[iwldntli2u]

Re: 1968 Mercruiser 120 Engine

Sorry to tell you fella NONE. I have an 81 120 and have tried the same thing. Best bet is to rebuild the engine of sell the boat off the parts and buy a new one. Some 120 parts are hard to come by.

 

[drgaul]

Re: 1968 Mercruiser 120 Engine

waterlauger i am new to the group. if you look at 120hp merc i/o upgrade just down from yours you can see all the replies so far. these guys are not like car guys, they dont like to do engine swaps you can tell by there replies. what i have found out so far is this. gearing in the upper drive is different 4cyl is 1.98, l6 is 1.65, v8 is 1.50. most chevy car or truck l6's will bolt up to the drive ( yours is the old chevy II not a volvo right), as well as all chevy v8"s except ls1"s, and 4.3chevy v6"s will bolt up to.you will need the correct flywheel for that engine-the local boat shop's tell me for a standard trans that fits the engine you are installing. also you will need the to install the hose's in the same location as on the l4 engine. the exhaust on your boat is probably water cooled. so you would have to get the correct water cooled manifolds new or used for the engine you are using. or you could get creative and use zoomies like on a race boat, that will be load but will work. motor mounts is another problem, you may or may not have to stregthen your mounting point where the mounts bolt to the floor of the boat. I don't think many people know each boat hull that well to be able to tell you. and the mfg probably wount or can't help you either. that means your on your own. this is a pretty involved, but it can be done. just depends on how carzy or how handy you are. the best way is to get a good used stern drive from the boat yards that matches the engine you want to install, and you may want to get a manuel on your boat to. now to the boring but required stuff. all boats have a tag someplace stating max horse power-take its advice or dont, may want to check the laws on this. also there is things like static electicity that can biuld up in the hull not to mention gas fumes and the fact you are in a big pc of wood and fiberglass. dont burn your self up, hot thing's ie exhaust and wood don't mix. more boring stuff-if you put in an engine that has less power and don't change to the correct gear these thing's may happen your new engine may bouuug down, and if your new new engine has more power it may over reeeevvv. you probably will not get any other advice from anybody except sell your boat and get something closer to what you want! remeber people said if we ran more than 60mph our chests would cave in, in 1909 that was proven wrong. they also said if man was supposed to fly he would have wing's, in 1903 they were proven wrong ect ect ect. if you feel confident and daring dive in or buy another boat. im daring. from 32yrs of making thing's with wheels go faster. ( ok guy's send the hate mail i can take it ).drg

 

[Bondo]

Re: 1968 Mercruiser 120 Engine

The Only Things that'll "Bolt-Up" is the merc.120hp, 2.5l, Or the 140hp, 3.0l....<br />Other than those, As dwain gaul states... The Sky is the Limit.. It Just depends on how Creative you want to Get....

 

[FreeBeeTony]

Re: 1968 Mercruiser 120 Engine

I am in the process of rebuilding a '67 Mercruiser 160. Bored out the block .030 over, new pistons, rings, bearings, recond the head/valves, converting to HEI distributor, etc....The engine is a GM 250cui, IL6, everybody says this is a great engine. It's very simple/easy to work on. I found a 1.65:1 pre-Alpha drive on ebay and will install new gaskets and water pump. Sounds like I am doing what you might need to do. It's kinda fun if you enjoy this kinda stuff. The parts seem readily available for this engine...

 

[WaterLauger]

Re: 1968 Mercruiser 120 Engine

Thanks for the replies. I know my brother (really, it is my brothers boat) isn't up for such an in depth project as that - he has an attention span of a three year old. He will want it to bolt up w/o problems, and hook the ski up. So, we either have a replacement 120 or 140 engine. Is that what I am hearing? <br /><br />Thanks in advance to any and all additional info.

 

[Bondo]

Re: 1968 Mercruiser 120 Engine

YES, the 120hp, 2.5l, OR the 140hp, 3.0l......

 

[drgaul]

Re: 1968 Mercruiser 120 Engine

bondos right he should not get to involved then. should not be to hard to find one.drg