[sailormanbigd]

hi, first post so please be nice.
I bought a boat 1 year ago, its been in the shop for almost the entire one year. Problem: motor runs and idles on muffs but when in the water it won't stay running, starts hard-have to use the fast idle lever. The mechanic has pulled the carbs three times, the lower unit a couple times, the intermediate unit-to clean it, replaced the main wirring harness, the timming base, one cylinder head and gasket(leaking) and it still does the same thing, wont run in the water. He said the next step is to dismantle the power head and go through it to see if they can find anything wrong. When i bought the boat the po said it was a rebuilt motor. the plate on the mounting bracket say's mod#140943R and ser #j0002840, on top of one side of the engine is a freeze plug thing that has 391227RPH stamped on it. From the mod # i would gues its a 140 hp 1979 evinrude. But, how do i be sure? could be a whole new power head and left the old tag? Anyway, I don't have the money to repower, or have someone else rebuild the motor. The boat goes good once you get it moving forward and running 1000 rpm or so, but slow down less than that and it acts like it wants to stall, rpm flucktuates, goes like hell after 1500rpm and reaches-if i can remenber, about 5500 rpm at wot.
i'm not a mechanic, but can take anything apart, and most of the time back together. Any help would be soooo apreciated. oh, the commpression is good in all cylinders. Any ideas what is wrong, or any wizard mech. near New Port Richey, Fl. ? Thanks

[ezeke]

The model number is in fact for a 1979 140 hp motor. The freeze plug may be for a replacement engine.

There is little about your engine that is beyond your skills if you have a model-specific factory service manual, time and some good tools.

http://cgi.ebay.com/ebaymotors/Evinr...spagenameZWD1V

Your motor does not have a high enough resale value to warrant continued service from a mechanic who cannot fix it.

[tashasdaddy]

to start, fast idle lever all the way up, pump primer bulb till hard. turn key to on, engage choke button and hold, turn key to start, engine should start. release choke, then you may have to bump choke button several times until the motor settles.

also the slow speed idle has to be set with the motor in the water and IN GEAR.

also what are your compression numbers.

[Dhadley]

391227 is the part number (it superceeds to 394451) for a factory replacement powerhead, hence the RPH. It's actually for a Sea Drive but it is basically the same.

Your smyptoms indicate a fuel delivery problem, possibly a air leak issue as a kicker. If compression and a leakdown test indicate a basically healtyh powerhead there is no reason to take the motor apart. In fact if he replaced all those things trying to solve this issue, those things were (obviously) not needed either.

Since it seems he's into changing parts rather than diagonosing the problem I'd try a known good set of carbs. If that's not it he might look at the reeds. Specifically the reed block gaskets to make sure they're on correctly.

[JB]

Typical of a V4 with an air leak into the crankcase(s). Check the gaskets, as Daddy advises, including bypass covers.

[sailormanbigd]

thanks all for the advice, if my motor is a repalcement power head what manual do i get? for what motor? I went out and tried to find a omc manual for 140hp 1979, but not at the auto parts stores i visited. The manual would be a significant help since i am having trouble with tech jargon in some of the replys. What is a leak down check? how is iot done? hoocked to what? I presume it is a vacuum or pressure test similar to chcking a radiator system for leaks?
My mechanic is a reputable one and is my long time friend. the problem is he has no time for my little repair...he's busy with the big dollar stuff in the water. he said my motor is basic and simple as did his son, both are graduates of a well known mech school.
they told me that they tried to set idle in the water for over 30 minutews.
I know the motor is old, or is it (rebuilt power head). And it has been the topic of my feeble mind and the loss of substantial sleep. I would like it fixed, but can't push the mech, cuz i can't aford a tear down for diagnosis bill. Thanks for the help, i must attempt to fix it myself, big learning curve.

[sailormanbigd]

i don't know the actual compression numbers, but they told me theey were good and plenty of compression, i think around 135? it was almost a year ago. why, or how is it that it runs good on muffs but not in the water? Back pressure on the exhaust?

[sailormanbigd]

EZEKE, THANKS FOR THE LINK, just bought and payed for the manual, hope it is easier to follow than the "SELOC" or haynes/chilton mans.

[Nandy]

Sounds like a mechanic that dont know what he is doing or is tryign to go to hawaii with your money. I had the same problem in a Mercury 500. It was a blown reed valve. In my opinion pulling the carbs one was ok, but most everything else he did seems to be unecesary. When it is runing in the muff check if any of the carbs are "spitting" gas. Either way, you need to get it fix yourself or take it somewhere else.
Good luck.

PS - I originaly posted this before reading the guy is your friend. If he is really your friend and would not rip you off then i think he is not such a good mechanic. I dont mean to be rude, but pulling a lowe unit for a obvious combustion problem? maybe he is just telling you he is doing that rather than tell you he have had no time to work on it...

[sailormanbigd]

ok (i keep rereadin reply's) what is a "kicker", and how do you check the gaskets, "especially the bypass gasket" I need help from a "cadet" standpoint. I only have experience with kickers for my sailboats, and i hated them, couldn't wait to turn them off and no peace-until i neede to start them up again. I searched throught 1146 items for evinrude on ebay and looks like i can get a reed block for around 100$, then i guess i will have to get the gaskets too? sorry bout so many questions but i am an obsessed person, been waiting for a year to take my family fishing, boating, wake boarding, etc.
oh, by the way the motor is pushing a 1984 Mckeecraft 18

[HighTrim]

The backpressure on the exhaust is the exact reason that there is a difference between the water and on muffs. The original manual is much better than the Seloc version. Set the throttle in gear under load like stated to 650. A leakdown test is also sometimes called a cylinder differential test . A leak down test pinpoints where you are losing compression and exactly how much. Doing a leak-down test diagnoses where you're losing compression before you open up your engine. You can do this yourself, but you need some specialty tools. You need to have compressed air available, as well as the special gauge. The gauge looks like this:

One face of the gauge measures the pressure of the compressed air
that you are forcing into the cylinder, and the other face measures the
percentage of this pressure that is being lost. There is a knob on the
gauge that lets you control the pressure going in so you get even results.

[metriccrescentwrench]

Additionally, a leak-down tester has a calibrated orifice such that a known amount of compressed air is going into the cylinder. Leak-down testers are routinely used in servicing piston aircraft engines. They're more accurate than a compression test because you can, for instance, detect a cylinder that's scuffed near the bottom which might not show up on a compression test. Somewhere not to long ago I saw an article on a simple home-made leak down tester. A quick google should turn it up.

[sailormanbigd]

ok, i have knowledge regarding a leakdown test. The info i have garnered suggest that the test is more definative when a compression test has indicated a problem,ie. low compression in omne or more cylinders. by listenning for where the air leaks you can determine the cause. But my compression check was good. Can an airleak test be performed on the fuel delivery system and detect a leaky fitting or gasket that way?
How do you set the idle in gear under load if the engine won't idle?

[F_R]

There is more than just compression involved with a two-stroke. Compression and leakdown is all about pressure above the piston rings. A two stroke also needs compression BELOW the rings (crankcase pressure). Some of the things affecting that have already been mentioned. Reeds, seals, gaskets. But the biggie is piston fit. The piston skirts are the "valves". If loose or scored/scuffed, the seal is broken and it is more or less allowing exhaust to blow by into the crankcase and/or allowing crankcase pressure to blow by out the exhaust.

You say the powerhead has been replaced. But what has happened to it since it was replaced? Has it been run hot? That will kill it in a heartbeat. Correct oil mix? Properly broken in?

I am not thrilled with the idea of working on a salt water motor that has dumfounded a qualified mechanic, but am in Sarasota if you want to talk.

[sailormanbigd]

talked to the mechanic this am. He says you can't do a leakdown test on a 2 stroke. There is .010 clearence of the rings/cylinders. he says it won't show nothing and how do you get pistons to tdc. Anyway he is letting me borrow his shop manual until mine arrives in the mail. I am going to remove the powr head and dismantle it to figure out what the problem is. He says that whoever rebuit it did a lousy job. Used worn out heads(i replaced one.) and the wirring harness was crap(replaced it too) and if they sent a motor out that way then the could have used mismatched parts inside. or something like that.

[Silvertip]

If what you are telling us is really what your mechanic is telling you, you really do need a different mechanic. You will also not find a decent manual for your engine at an auto parts store. Order one on-line. Your engine is an internal combustion engine and can indeed have a leakdown test performed. And lastly, there is not .010 clearance between rings and cylinders. If there was the engine would rattle like it had a handful of marbles in it and it would have zero compression. DO NOT TEAR THIS ENGINE DOWN. Diagnose the problem. You have been given a number of things to check -- check them. Cylinder heads don't "wear out". They warp due to overheating, get plugged up due to corrosion, plugged with sand/silt, or they get beat up as a piston or ring disintigrates but they don't "wear out". If the engine runs fine off idle to wide open then you simply have an idle issue that can be resolved with some diagnostic work rather than just thowing parts at the problem.

[Dhadley]

Ditto.

Especially if he doesn't know how to get a piston to tdc.

[Esox]

sailormanbigd,

Do yourself a favor and take the advice thats been given above. Some of the most knowledgeable guys here have given you great advice.

[Joe Reeves]

Your 1979 140hp Evinrude is no doubt a 20" shaft engine. You can check that by simply measuring from the underside of the transom brackets, where they sit on the transom, down to the cavitation plate (plate just above the propeller). That should measure roughly 20".

The idle rpm for that engine, running on a flushette, should be 1000 rpm or just slightly higher but not to exceed 1100 rpm. If it is idling lower than that on a flushette, in all likelyhood it will noit idle and will have a tendency to stall out when in the water due to exhaust back pressure.

The linkage between the craburetors should be set so that the throttle butterflies open and close at the same time. If set so that one butterfly is closed and the other slightly open, weird happenings will take place.

Is there any possibility that someone has been experimenting and had installed improper carburetors or jets?

The high speed jets should be marked 65C meaning that the inside diameter is .065. The slow speed jets should be marked 30 meaning that the inside diameter is .030.

The high speed jets are located in the bottom center of the float chamber, 2 to a carburetor. The slow speed jets are located in the side of the upper carburetor body, near the flange portion that connects to the intake manifold, behind those small aluminum screws. If the slow speed jet is not at that location, the craburetors are most likely from some other engine.

The throats of the carburetors must be a specific size and are usually marked on the front lower right side portion of the upper body. Memory fails me as to what the proper size is but I'm sure somone else can fill that bit of information in.

Let us know what you find.

[sailormanbigd]

hello again, thanks for the replies. Yes it is a 20 inch shaft. I really don't want to tear the motor apart, its my feeling that it is something minor, but not easy. I have had faith in my mechanics until now. They replaced the timming base and removed the carbs-cleaned them three times. If there was something amiss with the carbs then i would think that they would have found it.
WHen i first launched it and it wouldn't idle-i turned the idle stop screw all the way in and it didn't change the idle rpm at all. Like it wasn;t even touching the stop.
I don't know how to do a leakdown, even though several people have instructed me to do one. What if I found one cylinder low-or a higher percentage of pressure loss-then what would that tell me?
I did get a reluctant offer to check it out, but that is a fairlt long way from me.
What the mechanic also says that i should look for a used motor- a freshwater one, before spending the money to rebuild mine. The cost of gaskets, broken mounting bolts and having to heli-coil them, not to mention 100$ a piston, etc, etc.
I just want to take my kids fishing before there too old (now16 and 13)
I am divorced and child support(paying my ex's bills) has not left me too much "toy money". I have a 1990 chevy silverado for sale/trade for a motor or work on it?

[HighTrim]

If the information you are providing is correct, I wouldnt use that mechanic anymore. This surely does sound like an air leak into the crankcase, but dont go ripping apart the motor until you do some more investigating as advised. I would take FR up on his offer and talk to him. You may very well need some adjustments, including the throttle cam. Im not 100 percent, and others will be able to verify for me, but does your throttle cam have "START " marked on it? If so, when the warm up lever on your control box is moved to the START position, the START mark on the throttle cam should center on the cam roller. If it does not, turn the stop screw in the control box in or out to obtain proper adjustment. I say this because this needs to be done when the engine idle speed is changed enough to require throttle cable trunnion adjustment, and it sounds like you have been playing with the idle speed screw. You will then need to do a link n sync. This is to ensure proper spark advance at all throttle settings. Open the throttle to wide open and adjust WOT stop screw so that throttle valves are full open without strain on throttle shafts. Then connect a timing light to #1 cylinder. Start motor and advance warm up lever to show 5 deg advance timing. Stop motor and adjust throttle cam yoke to align embossed mark on throttle cam with the center of the throttle cam roller. Open throttle to WOT. Adjust full throttle adjustment screw to prevent strain on throttle shaft. A thin strip of paper between the roll pin and stop should pull out with just a slight drag. With timing light still connected, start motor and check timing as per your manual. Adjust the idle adjustment screw so the motor will idle at 650 max rpm in gear and under load, or about 1000 of the muffs like Joe said. If the timing pointer has been disturbed, you should also check it as per your manual. Joe Reeves will be able to guide you with checking your timing, he has a good guide for it.

[Joe Reeves]

It's unlikely that the mechanic meant there would be a clearance between the piston rings and the cylinder walls. I would assume he was speaking of the ring gap that must exist between the ends of the rings when compressed within the cylinder which is between a minimum gap of .007 with the maximum gap being .017.

No offense intended to anyone here but personally I have never performed a leakdown test. The compression test was most important to me, and if faulty, the engine was torn down completely to correct that problem.

[sailormanbigd]

update: yes motor does have a "start" marked on the throttle arm thing with two adjacent lines. I fired it up-after charging two new batteries and ran it. The idle was eratic, fluctuating from 900-1100 rpm. I sprayed carb cleaner around at different gaskets and found that if i sprayed the lower part of the intake gasket it would slow down and stall. It did this on both sides of the engine. Also, i sprits alittle in the carb throats-the upper would cause immediate drop in rpm, but i could give a much more stronger spray into the lower carb and hardly had any effect? Does this mean that the lower intake manifold gasket is loose/leaking? or just coincidence? thanks all for all the advice. Patrick

[sailormanbigd]

hi yall, i just started the motor, after charging my new batteries from sitting for 6 months. I sprayed gumout around the gaskets and found what i feel is a leak. When i sprayed the botoom of both sides of the intake manifold gasket it would drop rpm;s and stall the motor. Also, if i when i would put just alittle sprits in the upper carb throat it would stall immediately. But i could spray alot more in the lower carb and it wouldn;t hardly change rpms. Is this from leaking air at the intake base gasket?
Where is a reliable, honest, and reasonable parts source for my old omc. 1979 140hp 20"shaft with pt&t. thanks everyone. Patrick

Ps. I will be very upset if after they had my boat for 6 months it turns out to be a simple gasket-intake. Patrick

[R.Johnson]

You most certainly have a leak. Start with a compression test before you start taking thing's apart. Spraying into lower carb's without a change could be same problem, or something else. A compression test will save both time, and money.