A little help

[mill686]

It's been a while, because I have had no problems until now. I was out on the water the other day when I noticed my outboard started sounding like she was running improperly. Turned around and noticed no tell-tale. immediately shut it down and paddled home.

I dropped the lower unit and inspected the impeller. The impeller, which I replaced back in May when I repainted the lower unit, appeared fine a first. All vanes were soft and pliable. I then noticed that the entire body was split. Has anyone ever seen this? Could t be a defective impeller? I replaced it with a new one and cranked her up. Spitting water fine, but not idling like she did. After further inspection, I noticed a trickle of water from around the top spark plug. Don't ever remember this, but it cannot be good.

It is a 1984 50hp #6487117.

Thanks,
Greg

 

[b521]

I just had the waterjacket cover off of a different motor, but it may relate to your problem, as it deals with the area that seals right around the spark plugs. The cover around my plugs is a water jacket cover. It has two holes in it (as mine is a2 cylinder) that allow the plugs to come through. When you take that cover off you do not go directly into the combustion chamber. You go into the water jacket chamber. As a guess you got some impeller particles that went up through into your water jacket areas, probably restricting a drain hole or the pee tube (for the rooster tail etc., so being your pump is pumping good as you are (thankfully) getting water up to the powerhead and it is coming out a weak point (around the spark area gasket) , because enough of the water is not escaping from the end (downflow of where your water returns to where it came from,(the lake, either through the pee hole or the exhaust drainage area under your power head. then it may be a normal leak whereas all you may need to do is tighten that entire cover down , or first blow some air down the pee hole tube to see if you can dislodge some of those fragments ..then tighten it down.

 

[mill686]

Thanks b521,

I had no vanes come off. The entire thing was in tact, just split and no longer attached to the bronze inner ring. After removing that and putting in a new impeller, it pees water just like it used to, with force that increases or decreases with the throttle.

I wonder if during that time span that I made a 3 minute trek from a point on the river to where I noticed it, if it got hot enough to damage that gasket under the cover where the plugs screw in. Do you know if it is a metal reinforced gasket? I believe it is noted as the "cylinder block cover assembly" and its corresponding gasket. Could something have failed with that gasket around that plug? With water trickling from it, I would guess that proper combustion is not happening there and would explain the rough idle.

If I removed that cover and cleaned the old gasket material off, would I need to sand that cover to assure it is flat, or would a new gasket suffice?

Does this sound like reasonable explanation and fix?

 

[b521]

On mine it may be different. But lets assume they are the same, (as in yours is the same as mine) and it probably is cause you are describing it as a cylinder block cover. not a cylinder head) when you take that cover off as I described in my previous post, you do not get into the combustion chamber where the pistons are. as a matter of fact if you took those cover bolts off you could still leave your spark plugs screwed in and the cover will lift off right over them. Mine is a water jacket cover. when the cover comes off it looks like a shoe box with two halves of an orange in there with the plugs screwed into them. It is not like a 4 cycle car motor that has a detachable head. Why, because a 2 cycle has no valves in their head, it does not have any valves at all. It is not uncommon for a 2 cycle engine to not have the conventional detachable head like the head on a 4 cycle automobile head. All that cover is is a waterjacket cover that has holes in it that allow access for the spark plugs to be screwed into the top of the 2 cycle cylinder chamber. Very similar to the perverbial HEMI engine (mopar chrysler 426 HEMI) where as you can screw the spark plugs into the center of the valve cover , but if you take the valve covers off you are not entering the combustion chamber.
Now my disclaimer is if you got something different than I am not responsible if you tear it down and find yours to be a different configuration. So look at an engine diagram or wait till someone else chimes in.
Yes there is an expensive gasket under my cover and it gaskets the boarder of that cover and it spider webs gasket material over to the center holes. Do you need to purchase a new gasket, well that gasket only holds about a couple pounds (PSI). It would be like putting your finger over the rooster tail. really not a lot of pressure cause if your rooster tail clogs water will escape under a tad bit more pressure flow out the downstream of your cooling systen somewhere else water jacket system drain holes exhaust etc. I am working on other things on my engine so when I opened it up my gasket only ripped a tad so I coated it with black RTV. Cause I have other issues to solve with it and can’t be running out the door every time a need a disrelated expensive part.
1. Some people don't like rtv on marine engines, I believe they are correct to a point but in this situation there is nothing wrong with it.
I will tell you about RTV. I worked at a speed shop in the early 70's It was sponsored by General Motors . These cars are worth a gazillion of dollars today. RTV was just developed. What we did was take our intake manifolds off, grease coat the ports, put rtv on the heads and put manifold back on half tight, then tighten it down the next day. then when we had to change manifolds for different events or in the pitts we would take the old one off like a suction cup and the rtv stayed there glued to the intake ports of the heads and across the front and rear milled surfaces of the block and we never had to change a gasket and there is a lot of heat on the head of an automobile engine, (you don’t want to be scraping gasket off of a hot engine when you have to change from a 4 to a 3 barrel manifold etc in under 10 minutes and sometimes we would get like 10 changes before we would damage the RTV, So for a few pounds of pressure on that inspection cover of this area on an outboard bouat motor cooling system in the downstream(after the impeller) rtv ain't gonna hurt nuttin. so if your curious you may want to pop it off and pick out any debrie corrision residue etc then do the RTV in the correct procedure (there is a procedure ) then decide if you want to spend a gazillion dollars on that gasket cause I would bet it is expensive
Did you try tightening down the bolts on that cover. Aluminum is funny cause it expands and contracts in different places every time it heats up, So it in essence will sooner or later wiggle some bolts loose, Therefore is why sometimes you have to use lock tite on aluminum and all aluminum engines need re-torqued again after they sit overnight.. (the torque setting will change on aluminum engines when sitting overnight without being run and any heat up of the unit, (just sitting cold roomm temp. sometimes this is needed to do for several times over a couple days like on an extreme high performance highly sophticated high revving 12, 14, 16,000 rpm motorcycle engine. (sorry to bore you but was also a Honda Motorcycle mech when working my way through school). (also this is the primary reason that torque to yeild bolts were invented)and I hate them. But they have their purpose in this new garbach that auto manufacturers put out today .
for that cover you can use RTV, at least temporarily to satisfy your curiosity and learning curve. (It's really knowing whats under the hood that counts)
2. What pizzes me off is I was not smart enough to buy stock in RTV 50 years ago. It is sold every where including wall mart for 50 years, back then you could only get it at a big time speed shop and it cost 5 times as much back then as the shelf price today. (same as saying you really had to have a need to go out with todays money of like a 100 dollars to buy an 8 ounce tube of rtv, I think back then it was like 24 dollars a tube

 

[fastjeff]

Chinese impellers!


Jeff

 

[b521]

Chinese impellers!


Jeff

When I get to my good motors during the winter where can I buy good impellers, I have mercs and johnnyrudes.

 

[mill686]

I decided to remove the cylinder block cover assembly and inspect the gasket. This is what I found. The gasket around the top plug was almost entirely gone, and in many places you could see it was weak. This is an '84 and looks like this piece has never been off as no paint was even scratched on the bolts or around them. I also took a shot of the outboard below that cover and gasket. Does water flow around all of the cylinders in that cavity? Is that the water jacket? BTW, only broke 3 heads off.

The newer gasket is beefier and provides full coverage (27-43777 on this site).

 

[b521]

yes you are looking at the water jacket. Like I told you it will look like 4 boobs in a shoebox. Its hard to tell from the outside that the plug does not indeed screw into that cover, (ain't it).
also important to note , that is not your entire system up in the power head, there is side covers, called inspection covers where it directs water to different places in your powerhead, it is like a rats maze and puts the proper amounts of water flor to the proper arears, first and second and third, in short it kind of makes sure some water gets pre heated in other areas before it dumps cold water right onto the cylinder head like if you were on a cold lake in winter so you don't crack anything, at least merc does this on their smaller engines there by eliminating the need for a thermostap. It's pretty ingenious.

 

[mill686]

That is really ingenious. Always wondered why there was no thermostat. So what do you think...is that bad gasket the reason for that trickle from the top plug?

 

[b521]

Ha HA , I hope so, I am not familiar with your exact engine so I could be way off in my thinking. Unless you have a crack somewhere in the block casting. which if you do would be a serious problem, first put on a new gasket, clean everything up and wire brush and oil those thread bolts. then every once in a while grab a 1/4 inch ratchet , with a 2 inch extention the proper size socket and and grab the ratchet up at the head of the ratchet and act like you are tightening down your outside water spigot for your garden hose. (twisting motion, not putting your hand down on the end of the ratchet which will give you too much leverage same as force. ( you are babysitting here for awhile not necessarily doing your final tightening , ) all this may not be necessary, but it seems you are concerned. so its your call, somewhere betweer if it ain't perfect then make it better or leave well enough alone, your call. )you know twist about 5 pounds of force, so as not enough to disturbe the bolt's sett but to see if there is any slack that developed that you want to make up for. But to add my 2 cents, I would say it is a good bet the age of the gasket along with the bolts loosening up, I know you indicated they were tight, but were any sort of loose to come out, They could be tight coming out but the reason for that could be the reaction of the bolts to the aluminum threads in the casting (engine block) ( a reaction called Dis-similar metal reaction) (if they are steel, zinc plated whatever, I can't say I have run into any aluminum bolts on this engine, But that is why the bolts would be tight seem tight but they actually corroded in place after they did their natural wiggle loosening which as posted before, aluminum is famous for. Doesn't matter because it is an easy to get at job, and there is really no pressure there unless your impeller is a very fast flowing pump.
now just cause there is not a lot of pressure thereby being weak to create a force leak.. thats only half the battle. if you have a system that needs to work, In this case create fresh cool water flow. and it is not designed to have a lot of pressure in the first place then a little leak will really drop it's effectiveness fast.

 

[mill686]

Thanks b.
Some were not very hard to get out. I did apply slow, steady pressure, but still managed to break 3. And yes, they were all corroded. I ordered new bolts and a new gasket. Do you know what they are supposed to be torqued at exactly? If not, I will cinch them up like you mentioned. I always thought torqued bolts should be done in thirds. Is that true?

 

[b521]

yes thirds is good. However this is not a critical torque area, you can be a little off per bolt ( some human varience) because it is not feeling the explosion like a cylinder head (on a 4 cycle auto engine ) nor the trauma of the explosion and vibration of a crank bearing or a conn rod bearing, nor the heat of any of these forementioned areas, I will try to find a spec as i have an old merc manual, it leaves a lot to be desired. it is probably going to be in inch pounds, which you need a pretty good instrument to do inch pounds, you can really do inch pounds in this area, by feel. I like to use the twist motion as mentioned up above on inch pounds cause it is scaled down so much grabbing at the center it is , well the best way I can explain it , it is "precision" (more precise) so if you want do it by feel , let it sit for some time maybe a day, lets the gasket shrink down then cinch it up, then after the first few times you run it, cause the heat will change it again. (maybe maybe not, but probably. See what happens, I have done a lot of aluminum notorcycles on a bwork bench and checked them the next day and have found more often times than not it was like i only snugged them and forgot to do a final tighten. Problem with them is you have to try and stay from a thread locker as the covers are all philips screws and you can only get so much out of a hand impact hammer. I would not use a thread locker where you are working, you should also cinch up those side inspection covers while you are at, it is part of the system you are working on, and I am sure you want to come out of this completely perfect. good mad
ttul

 

[b521]

The torque for my block cover is 70 inch pounds. It has 1/4-28 bolt and nut set-up. (Quarter 28). If you heve 5/16th bolts then the book says it is 90 inch pounds. I do not know what your 50 HP would be. Mine is a in the 10 hp generation, so maybe you can use that as a minimum amount of torque to use. 50 h.p. may be the same, duno.

 

[mill686]

1/4-20. I thought I read something once about 80 inch/pounds for mine, but not sure. Thanks for your input.

 

[mill686]

I did purchase new bolts, but I will heed your advice. Thanks .

 

[b521]

1/4-20. I thought I read something once about 80 inch/pounds for mine, but not sure. Thanks for your input.

as stated above My cover bolts are 1/4, 28, . same as saying Quarter 28, (note it is a fine threads have the power to strip faster under the same pressure as say a quarter 20, ((don't confuse anything I am saying here with crossthreading , that is a totally different animal)) why ? cause they are in essence geared down,, they would be like dumping your clutch in low gear as compared to dumping your clutch in third gear,, powerfull car, you blow a rear end, or tranny, or u joint, you dump it in high gear you may just stall out, whatever,, always heed your thread power on an aluminum appllication. (another trait , a good trait is fine thread, they have is they hold better under different applications such as a vibrating motor of which is aluminum. (aluminum sucks as a motor , but you have to use for boat motors, motorcycles, airplanes etc cause it is lght weight. as previously said my cover bolts are all a nut and bolt set up. Another little piece of trivea is that when you run into a nut and bolt set-up , When loosening them, the nut is where you are suppose to loosen, the bolt head is preferred just to hold the bolt when you loosen the nut first. You cannot always access the nuts in some situations, then your stuck working on the bolt head. It goes a little bit further in design as that is why you find a lot of nut and bolt assemblies having the bolt having a Phillips head or a splined head (a.k.a. wrongly called but currently accepted everybody calls them Torx head fastener. ) (why cause Torx is a brand trade name that stuck) These types of fasteners have been around in heavy metal manufacturing since the turn of the 20 th century. All they called the tool to take them out was a spline wrench. very similar to the front of a manual transmission on an automobile where it goes through-the through bearing and into your clutch anf finally the flywheel. "it is called a SPLINE' not atorx shaft..
summary that cover is not a part of the rocket science of your motor, what I did there on mine (and i am pretty particular when it is necessary, in this case, not necessary to be ) was re-use the old gasket with RTV ) cinched them up, made sure I did not get faked out and overtighten them by holding the center of the ratchet. Ba Ta Bing. It's dome. I have a guy down the street who can't do anything on a car except wax them, after he gells his tires he will grab his hydraulic jack and make sure all the RWL tire insigneia's are at the same place for all fout tires. I told him that if he don't make the equal number of turns in his driving all the time , then he won't be lined up and nobody is going to notice anyhow, He don't care, he likes doing it,, enough said. then he goes in and watches the NASCAR farces. typical oil changer that wants to be a mechanic. Boy am I going to take flack on this. Just let me tell you one more thing. did you know that the car that won Daytona in 1959 , had a 1 mph average lep time faster than the guy who won it in 2007, in his lightweight tube dune buggie plastic gocart. back then they had to be finate on their details, today it is just plug and play.
ttul (don't sweat the details here) on this particular job, save it for when you need it.

 

[mill686]

Good stuff B. I'll let you know what I find when I get the new gasket installed and the outboard buttoned up.

 

[mill686]

Put the gasket on yesterday and cranked her up. Seemed to be running just fine. Dropped her in the water and tied her to the pier. Went back later to find she wouldn't crank. Intermittent and weak activation of both the push choke/primer and the starter. Could my ignition switch be bad? Solenoid is less than a year old.

 

[fastjeff]

Bad connections at the battery?

Jeff

 

[mill686]

Checked battery connections and both were good an very clean. Purchased a new switch today. Switch was about 3 years old on a boat that sits in the water from April through December. All is well again. Thanks for everyone's input.