1984 Mercruiser 2.5

[Cbender]

Hello all, I am a newbie to the I/O world. I have just purchased a 1984 Cobia Odyssey 170 VBR with a 120hp Mercruiser 2.5. The first thing I am doing is changing out the impeller, thermostat and flushing out the coolant system, and gear oil. Then I am looking at a good tune up. Looking over many post here, what would be the best things to do to have her at her most reliable? Can you swap out to better plugs, hotter coils, etc? Or are basic stock parts the best route. This may be a dumb question, but like a car engine, can you make it better with after market parts? Again, forgive me if I just ask something dumb. Overall she is extremely clean and in great shape. She just runs rough at low idle and is desperate need of a tune up. I appreciate any and all suggestions, tips, and comments. I look forward to hearing from everyone!!

 

[Bondo]

Or are basic stock parts the best route.

Ayuh,..... Welcome Aboard,.... There ain't no special aftermarket parts that'll make yer motor go any faster/ more powerful,....

If ya got points in the distributor, goin' to electronic is a major improvement in most folks eyes,...

Addin' a water seperatin' fuel filter is a Great idea on any barge, especially since ethanol fuels,....

Otherwise, stay stock, 'n stay reliable,....

 

[thumpar]

I agree with Bondo. I had a 1983. The only thing I changed out was the ignition to electronic for one less maintenance item every year.

 

[Cbender]

That is a good idea, I was looking at a hotter coil but electronic would definitely hit better and less moving parts! I have an 85 Dodge Ram and she has electronic vice points. Makes life easier!! I wasn't looking at more power, just more reliability. I've been around outboards my whole life and 23 years in the Navy, I understand in water to get more power you need a bigger engine, period...... Anything else is a waste or marginal results at best. (I enjoy people trying to kick out more HP in marine engines like we do with trucks. Different animals!!) I am definitely more reliability oriented to enjoy the day fishing than scraping more HP from a 4 banger. I have noticed the Mercury manuals I have downloaded are not as easy to follow as outboard manuals or Chilton/Haynes. I'm still reading alot so hopefully soon I'll be more educated.

 

[Bondo]

I understand in water to get more power you need a bigger engine, period......

Ayuh,..... A 350 Chevy is a good base motor that can build from 230 hp to over 400 hp, if ya wanta do it Right,.....

A little 4 banger, is just that,...
With a big enough wallet, you can build horsepower, but ya can't buy enough Torque,....