Oil On Plugs

HappyHillbilly · Mar 13, 2005

Howdy! I just got a '79 Johnson 140 on an '85/16 ft. Procraft fish & ski. I changed the plugs using the QL77JC4 before I took it out for a test run. With 4 people, about 520 lbs. total, it pushed the boat plenty good enough for me. The speedometer read about 38 mph. I would hit WOT & then back it off just a hair to play it safe. Ran that way close to about 60% of the time, the other 40% was at about half-throttle or less. I ran the motor for about 2 - 2 1/2 hours total. I wanted to decarb before I put it in the water but didn't take the time to do it. Boat's been sitting here for a week before I even tried to crank it to see if it ran and the wife & kids were getting anxious. Anyway, I was well pleased with the way it ran & handled but when I got home & checked the plugs all of them had what I would call "oil marks" on the ends of the threads & one even had a small pool of oil on the outside of the head, at the spark plug hole. The firing contacts were clean on all of them, though. I used 87 octane with Pennzoil Marine Premium Plus at a ratio of 28 ounces to 10 gallons, which I thought was a little heavy but wanted to be safe until I got to know the motor. I guess I'm asking ya'll to confirm my suspicion that I need to rebuild this thing. If that's the case, replace the rings or go all the way? I realize that a lot depends on the condition of the cylinder walls but in general, what usually needs to be done in such a case? One other thing: The prop says - 389512 and 12 3/4 X 21. Is this the right prop? I've heard that some people use a higher pitch to help on hole shots but it's bad for the lower unit. I'll be doing some skiing but want to protect my investment, too. I'm sorry for my ramblin' on, I'm trying to give you as much details as I can in one shot. You're help is greatly appreciated! HH

Solittle · Mar 13, 2005

Re: Oil On Plugs

HH - Before you go rippin it apart could you tell us your RPMs at WOT and the compression for each cyl?

HappyHillbilly · Mar 13, 2005

Re: Oil On Plugs

One of the things I forgot to add in my original post: Tach doesn't work. On the compression, I came a hair from buying a gauge the other day but thought I'd borrow one instead of spending $50 for something I don't know if I'll need but once or twice. I ordered a manual from here this morning (Premonition?), I'll trace down my tach problem & get a compression reading one way or another, this week. I've got too many irons in the fire already so I'll not be in too much of a hurry to tear her down. Thanks, SoLittle

HappyHillbilly · Mar 17, 2005

Re: Oil On Plugs

Okay, compression test results: Starboard-top cylinder - 135 Starboard-bottom - 132 Port-top - 125 Port-bottom - 122 (Sorry I don't know the cylinder #s) I was unable to get RPM at WOT due to the tach in the boat only has 1 - 4 settings and it doesn't appear to be connected. I'll get one the next day or so & will post that info ASAP. The oil deposits on the plugs are so heavy after only a few hours running time. The only thing I can think of is that there was about a gallon or so of gas already in the tank & I just added 10 gallons/28 ounces to it. I will drain all of the gas out, run Seafoam through it & start fresh to see if it makes a difference. I also tested my rectifier, I believe, by checking the battery voltage before cranking & then checked it while running. Before cranking, the battery read 12.84 volts. While running, I got 15 volts on a fast idle & it even went up to 16 when I slightly bumped the gas up to see if it made a difference. Is this OK?

Solittle · Mar 17, 2005

Re: Oil On Plugs

Don't rebuild that engine unless you have nothing better to do with your time & money. Compression is the best indicator of the condition of internals and yours is just fine. I would do the decarb when you get time. Charging system is OK. Post the RPMS when you get it. What have you done to the engine since you got it? Do you have the OMC shop & parts manual?

DHPMARINE · Mar 17, 2005

Re: Oil On Plugs

HappyHillbilly., Is the motor still running good? Oil on the threads,and even in a small pool outside the head is a sign of sparkplugs that have been reinstalled too many times,or I think in your case,never torqued tight enough.Buy a new set,install at 18 to 20 ft/lbs,and use it. Then we can address your other points. Sofar,I doubt you ned a 'ring job' DHP

HappyHillbilly · Mar 17, 2005

Re: Oil On Plugs

Hey, SoLittle and DHPMARINE! Thanks for taking the time to help! I haven't done anything but change the plugs, and that's all I want to do, if you know what I mean. I was surprised when I saw the compression results. I was wonderin' about the difference between the 135 & the 122, if that's something to keep an eye on or not. I repeated each test 3 times per cylinder & got same results each time. I've got the Seloc repair manual I ordered from here. I'm going to try to pick up a tach tomorrow afternoon and I should have the RPMs at least by Saturday evening, if not tomorrow. I put the QL77JC4 plugs in it before I took it out, but I didn't torque 'em. Truthfully, I didn't know I should. I snugged 'em down but didn't put a whole lot of pressure on 'em so I wouldn't strip the holes out. I've been known to overtighten things so I played it safe. That's a good point, DHP. I'll also try to pay close attention to see if the plug hole threads seem good or not. I thought it ran pretty good when we took it out. After we got it back home & I checked the plugs & saw the oil, I put 'em back in, without cleaning 'em, and I noticed it running a bit rough, & understandably so.

HappyHillbilly · Mar 20, 2005

Re: Oil On Plugs

I've hit a snag on getting my RPMs at WOT. I got a tach and I'm trying to hook it up. The old tach in the boat wasn't hooked up so there wasn't an obvious gray wire for me to use. There is a gray wire under the dash, (doesn't run through the switch box.) & it's hooked to the "Lights" switch. Am I to use this wire or should the tach have it's own direct circuit? At the terminal block on the motor there are 7 terminals and they are as follows: (Starting at the top & going down) T1 - Empty T2 - 2 Yellow wires T3 - 2 Yellow w/gray stripe wires T4 - 1 Gray wire (runs under flywheel & appears to go into boat) T5 - 2 Red wires T6 - 1 Brown (looks to be brown but could be gray) T7 - Empty With a tester, I get a "complete circuit" reading between T4 & T6. Also, there is a 3 prong plug that plugs into the switch box. Mine only has 2 wires in it, 1 is a ground & no reading on the other. Any thougts? This boat is only rated for an 85 HP, I believe, and I'm sure some mods have been done to be able to use this '79 Johnson 140. Thanks, again for your help! HH

Silvertip · Mar 21, 2005

Re: Oil On Plugs

In your first post you said the prop was a 21 pitch and that you were told higher pitch will help hole shot. Thats not true. Less pitch helps hole shot. Higher pitch increases speed. Before messing with props you need to know what your wide open throttle rpm is. If its in the correct operating range, you are already propped correctly.

HappyHillbilly · Mar 21, 2005

Re: Oil On Plugs

Thanks, Upinsmoke. I may've been told the right thing about the prop size but got it twisted 'round, myself. It's happened before.

Before messing with props you need to know what your wide open throttle rpm is.

Thus the reason for my last post. Thanks for taking the time to help keep me in the right direction.

I think I've got it figured out, now all I need is the time to do it. I've cleared my schedule for the rest of this week, after today, so I can get the things done to the boat I want/need to. Catch ya later! HH

HappyHillbilly · Mar 28, 2005

Re: Oil On Plugs

I finally got the RPMs at WOT. 5400 RPMs. Cruising at 45 MPH. I decarbed it and tightened the plugs a little more than I did the first time & everything seems fine. My manual (Seloc) lists 5000 RPMs at WOT. It doesn't list a range. I'm well pleased with the boat's performance so I'm not looking to increase speed or anything, I just want to keep it within safe operation. Should I try another prop or does this setup seem to be OK? Thanks! HH

rayjay · Mar 28, 2005

Re: Oil On Plugs

Usually there is a little plate on the starboard side of the motor { on the tilt bracket] that has the WOT rpm range on it. Your's is probably 5500 so you are perfect.

DHPMARINE · Mar 28, 2005

Re: Oil On Plugs

HappyHillbilly, Just reread some of these posts,and what I missed is the boat is rated ONLY for 85HP.To assume the boat has been modified to handle an additional 55HP is a long shot You seem to be dangerously overpowered. Sorry to say it,just don't want to see anyone hurt. DHP

HappyHillbilly · Mar 28, 2005

Re: Oil On Plugs

rayjay, You're right about the RPM range being on the motor's ID tag. Mine happens to be on port side but it does say 4500-5500, just like you said. I'm sorry to have wasted your time by overlooking it. DHPMARINE, You were right about me not having the plugs tightened down enough. As for the boat being dangerously overpowered, don't apologize for your concern, the world needs more people like you. Now that I know a little more about the boat & boats, in general, I'll research again & try to find out for sure what it's rated for. What are some of the dangers of too big a motor? Thank you, both! HH

HappyHillbilly · Mar 28, 2005

Re: Oil On Plugs

Okay, I goofed on the boat's HP rating. It's rated for a 115HP. I must've got the 85 from the year. I've been so busy the last month or so that I've been transposing a few numbers here & there. Been back & forth on the boat & motor years; like looking for parts for an '85 motor and thinking it's a '79 boat when it's vice-versa. I'll blame it on being busy but there's a good chance age might have a role in it.

llfish · Mar 28, 2005

Re: Oil On Plugs

There are a lot of us in the world that have the age problem but will not admit to it. Take a Coast Guard Auxiliary class and have a safe summer boating,

Oil On Plugs

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