1977 Johnson 140hp low compression

[cvtech1]

I have a 1977 Johnson 140hp 4cyl, that has one cylinder that has 25psi. the rest are good. The shop says rebuild it all. It ran great to me but did seam to have some starting problems at times. It ran at 30- 35mph with four adults on this 1977 17 ft Glastron bowrider. My question is does it need a complete rebuild, what to watch out for and what kind of price am I looking at? I am in the Houston Texas area. Any advice would helpful. Thanks

 

[SparkieBoat]

Re: 1977 Johnson 140hp low compression

I am not sure on the cost..but if the other pistons/rings are the originals they are pretty old and i think you would be wasting your money to repair only one cylinder. you can try replacing the head gasket first..dont forget to sand down the head..use a piece of 400 grit sand paper taped down on a 1/4 piece of glass. My suggestion to you is to go buy a used 90s model 150 V-6 or 175..they are the same weight as the newer 140s..(I think your 140 is the same as the 115 blocks about 330LBS and only produced around 120 at the prop.) but the post 1980 models are a heavier block at around 370lbs..which is about the same as the 150-175s. Even a 115 would be a good option for you if power is not a big issue..probably as fast as the one you got now. I have even seen a few 2000-2003 models for sale for under $2K..i recently saw a 2001 4 stroke suzuki with low low hours for $2500..the optimax and E-tec Evinrudes are pricey but who knows you might even pick up a deal on one. I would steer clear of the Fitch motors though..even though they did not have problems with all year/models. Even a good Yammy would be in my search. just my humble opinion that unless you just are emotionally attached to your 77' 140 or can do your own rebuild...a good used motor is your best option if the head job does not work.also while you got the head off look at the cylinder wall for scoring and check for piston slop...good luck

 

[R.Johnson]

Re: 1977 Johnson 140hp low compression

First take the head off, and see why that cylinder is low.

 

[kenmyfam]

Re: 1977 Johnson 140hp low compression

Agree. Don't jump straight into a re-build. Could be as simple as a stuck ring.
Have you tried a thorough decarb and checked compression again afterward ???

 

[emdsapmgr]

Re: 1977 Johnson 140hp low compression

As RJ said, pull the head. Check to see if the head and piston crown are pitted from piston ring debris. You can also pull the side bypass cover (on the cylinder that has low compression) and inspect the side of the piston.

 

[cvtech1]

Re: 1977 Johnson 140hp low compression

Thanks guys, I wish I would of read the replies before I gave the shop the go ahead. The price is $1800, and Sparkieboat if I knew I could of found a motor close to that price what would the hookup price be? Anyone, can you tell me about that price with all the pistons replaced a new water pump? This is a great boating place thanks all.

 

[cvtech1]

Re: 1977 Johnson 140hp low compression

I checked online in Houston and did see some early 90's model outboards and they where about 2500-3000 dollars. I still would like to know what the rigging would cost and should I have choose better. I love the boat and just want to have a dependable motor. Any thoughts?

 

[jonesg]

Re: 1977 Johnson 140hp low compression

Find out why that cylinder failed or it will fail again,

and thats not a bad price for a complete rebuild.

 

[emdsapmgr]

Re: 1977 Johnson 140hp low compression

If you know the mechanical history, the engine is otherwise sound and you have a sentimental attachement-overhaul it. Generally overhauls are cheaper than engine upgrades, considering rigging conversions-tach hookups, etc. If you want more power, there are many solid V6 engines available that will plug right into your control box. A base 150 has significantly more torque and power than your 140. Your 77 140 is a unique hotrod model from OMC. It is the only crossflow V4 with an exhaust tuner in the midsection. The high compression heads made it a solid performer in it's day.

 

[SparkieBoat]

Re: 1977 Johnson 140hp low compression

Keep your eye out for a deal on a newer motor. after you see one advertised for more than a couple of weeks call them up and make an offer of $1500-1800 cash..be sure to check out the compression and sparks before you buy..if possible take it out and run it first.I have even seen 2001 models here for under $2500 with low hours...here check this link out..if this motor checked out I would offer him $900 he would take it for sure.
http://houston.craigslist.org/boa/1398891120.html
you would be doing the boot scootin boogie with that baby.

 

[cvtech1]

Re: 1977 Johnson 140hp low compression

Thanks guys, the boat is still in the shop and I will let you all know if it turned out fine. I will be sure to ask why it failed. I will more patient next time and seek the advice available online before making a quick decision. By the way what kind of engines would hook right up to my controls. Great forum thanks.

 

[emdsapmgr]

Re: 1977 Johnson 140hp low compression

Your control box will mate up to OMC engines through 1995. The 96 and newer engines will also work, but you need an adapter cable to plug into your existing red plug wire harness.

 

[cvtech1]

Re: 1977 Johnson 140hp low compression

Thanks for the control box advice, very helpful.

 

[jonesg]

Re: 1977 Johnson 140hp low compression

FWIW I paid $1500 for a 1994 Johnson 150, another $300 for controls w/ tach. Runs strong, lotsa power. Mine is a commercial, I think that relates to the lower compression (85psi) and a hefty gearbox which can turn a bigger screw, slightly lower rpm but good for dragging docks around.

 

[SparkieBoat]

Re: 1977 Johnson 140hp low compression

thats a fair deal as long as the engine runs good..I think commercial is only a heavier lower geared foot..I may stand to be corrected on that. But you should be able to change your prop pitch to adjust, lower the pitch to get higher RPMs..you should be at around 5500-5800 RPMs at WOT..about 200 RPM change with each inch in prop pitch..bigger pitch number = lower RPMs,

so what is your RPMs at WOT??? you want to test it with an average expected load. (kids, coolers, ect.)

 

[cvtech1]

Re: 1977 Johnson 140hp low compression

I am ordering an extra prop online for my 1977 johnson 140hp what type should I get? Thanks guys!

 

[cvtech1]

Re: 1977 Johnson 140hp low compression

I received my rebuilt motor back from the shop and it ran fine. I have been out several times and it ran fine after I finally started it, had to make a call to get advice on how to start the thing. I will be starting it cold a couple of times a week till I get it down packed. Going fishing Friday morning, wish me luck. Thanks for the info.