Will It Blow Up, Or Will It Not Blow Up, That Is The Question!


I've been doing allot of research on the Internet concerning what they call the Balance Assembly, which is found on all Yamaha F150 Four Stroke outboard motors.  It may be found on other four strokes as well but, I am only concerned with this unit as it is the motor I currently have.  The reason for this article is that I have seen many other boats in the Interior, and the Coast, with the same motor on them and no doubt there's another 100,000 plus out there somewhere.  There is a imminent time bomb in some of these motors, and it could cost you a good chunk of change if in fact your motor is one of those with the problem in it.

Pictures above is the Balance Assembly, and its located on the front of your motor (remember we're talking F150's here) and right behind the fuel filter.  I'll keep my terms "lamen-ish" to make it easier for non-mechanic kind of folks to understand.  Most four stroke engines in cars/trucks have what is called a Harmonic Balancer.  Basically its a big chunk of iron made into a circle that attaches to the end of the crankshaft of the motor.  Its purpose is to "balance" the crankshaft and reduce vibrations, hence smooth out the motor and make everything run true.  The Balancer on the F150 serves the same purpose, except its contact with the crankshaft is via a large gear on the crank that then turns the Balancer assembly and smooth's it out, making everything run true.

The problem Yamaha had with some of its earlier engines, and I can't give you dates as no one seems to know, is that they used some bad material in making the fiber gears that are on the shafts.  The newest motors of course have been updated with the new part that does not have the problem.  The teeth on the gears break down and shred, which of course then go into the engine, the oil pump, and oil holes in the motor and plug it all up, subsequently then blowing the powerhead right outta the motor!  Yamaha recognized some of the problems and repaired or replaced the faulty units however, many were not replaced as they were not recognized by Yamaha as having that problem.  Boaters went for years with no issues but then a funny whine started to be heard at the front of the motor, this whine can be heard on You Tube (http://www.youtube.com/watch?v=W36GhDLez8c) if you just type in F150 Balancer Whine, and you'll see how noticeable it is.  Unfortunately, many of these boaters were not aware of the problem and kept using the motor until that gear finally gave out and kabloom, motor was toast, and no warranty.  You can see on the assembly to the right the fiber gears and the different colors, I'm assuming different material and I have no idea why they use fiber against metal but there is obviously some reason for it.

Did I have the whine in my motor???????  Well, after reading all the disasters that boaters had with this issue, I developed "OCD Whineitis" and thought I started to hear it, maybe, I don't know.  What I do know is that the problem was always on my mind, "Is this thing gonna calve out here or what????" and subsequently, I took the proactive approach and replaced the danged thing anyways.

I did much searching on the Internet for the product, which of course is from Yamaha, no aftermarket stuff for this baby, and because it has the usual "Marine" stamp on it you can be sure it's not cheap.  Well, not cheap in Canada, with prices ranging from $490 to $600, plus tax, plus shops wanted 3-4 hours of labor to install it, citing all kinds of nightmares if you tried it yourself.  That's where the Internet again came into play, a search in the USA found me the Balance Assembly in Florida, delivery to Washington State included, for $300.00.  The decision to replace it was now even easier with a reasonable price AND, I found some very easy to follow instructions (http://www.simyamaha.com/category_s/2871.htm) on the Net as well.  Hey, we were planning a camping trip anyways, so we headed down to Washington, had a great time camping and picked up the part on the way home.  Speaking of cheap, diesel ranged anywhere from $30 to $40 cheaper a tank down there!!  Anyways, following are a couple of pic's with what was required to do the swap, took me 1.5 hrs and a few beer breaks.  No rocket science to replace it, a 10 and 12mm socket and your done!  There are some specific instructions on the document that can be downloaded to explain how to line up the timing gear and the appropriate marks on the Assembly,  for anyone doing this procedure read up on it there.

The Procedure:

The obvious first, take the cowling off, remove the "snap on" timing gear cover and the cover that is overtop of the spark plugs.  Take the plugs out, your going to have to turn the motor over by hand at one point and its muchhhhhhhhhhhh easier with the plugs out.  OK, now the 10mm socket, take off the fuel injection air box, that big black thing, you'll need an extension for some of the bolts.  When I'm taking stuff apart I put each part and associated bolts together in one pile, no need to be losing or getting them mixed up with other parts.  Airbox is off, next thing is to get that fuel filter assembly out of the way.  You don't have to be disconnecting the fuel lines or anything that difficult, just take out those two 10mm bolts you see and move the fuel filter down and off to the side, now you can see the Balance Assembly more clearly.                                            



The last thing to move a bit is the electrical panel, that's to the right of where the fuel filter was and is held on only by 3 bolts, yup, 10mm socket again will do the trick.  It won't move entirely out of the way but enough that you can get a socket on that bottom bolt on the Assembly.  Move that to the side and now the Assembly is fully exposed and ready to be removed.  I used to rebuild my own motors and those on my folks farm for many years so while this wrenching may seem a little scary to some, trust me, this particular procedure has to be one of the easiest I have ever done.  The neat thing is when you do remove the assembly, you wind up staring right into the bowels of the motor, crank, connecting rods, whoooooooppeeeee!!  If you look at the picture you can see a big gear near the top of the "hole", that's the gear that connects to the Assembly and turns it all.  I did a quick inspection while this cover was off, getting a flashlight in and down to the bottom of the "hole", just to see if everything was tickidyboo, and it was, all nice and clean and no fiber material seen anywhere that might have been from the fiber gear.

The nicest thing about putting new parts in rather than fixing the old one and putting it in is, minimal clean up.  Once I cleaned off any old gasket goo on the motor (hardly any!) I use brake cleaner to make sure the surface is clean of all oil.  I also clean the new surface with brake cleaner.  Something the instructions do not tell you but you should do anyways, is pour a little bit of engine oil onto all the gears and spin them, no point in having dry gears right from the get go.   The tolerances of these motors is extremely tight, and by tolerances I means the space between stuff.  The surfaces of the two mating surface, that big "hole" and the new Assembly, must be spick and span before reassembling them.  They fit so perfect together that any piece of junk that is on the surface and not removed will prevent a proper seal of the Assembly, and then you have an oil leak and that's not a good thing.  Although, it would still be better than the motor blowing up if you caught it in time!  The instructions I downloaded online are great, easy to follow, and give all the torque settings for the bolts when you put them back.  A torque wrench is a must, when building motors every bolt has a certain torque to ensure it fits the part on as tight as it can, without breaking anything.  The instructions call for a anaerobic sealant, I used Loctite 515.  This stuff is not really silicone but what it does is seal without exposure to air, in other words it doesn't need to "set up" in the air like silicone does.  You also use very little, and I mean very little, because you do not want extra sealant going into the motor when you torque everything down.  This sealant could get into the oil pump or oil journals and plug the holes that provide lubrication to the motor.  I put a very small amount on assembly surface (not on the main motor surface!) and then smeared it so there was just a small amount left.

When you put the new assembly back onto the motor, there are two small studs that stick out that make it very easy to align, then hold it in place and get a couple of bolts put in to hold it.  Once you get all the bolts back into their holes, and they're all the same size and length so its easy (well, there are two small bolts but you can't very well put them in the wrong holes!) then get your torque wrench and follow the tightening procedure and ft. lbs shown on the chart, very very very very very very important, and its very important too!  When your all done the assembly should look something like this picture, where you can just see a very small bead of the sealant coming out from the sides of the Assembly.  That's the red stuff you see just around the edge of the new Assembly.  The instructions that were online said to put it all together and then start it up to check for leaks BUT, DON'T DO THAT!  The sealant requires a certain length of time to cure, and although 6 hours was a figure given I went with 24 hours, I'll be danged if I'm going to rush starting it just to have it leak because I didn't wait a few hours more.  Put back all the stuff on you took off, in the reverse order, and then let 'er sit and cure.  I cranked the motor up the next day and its good to go, no leaks and hopefully trouble free for the remainder of its days!  When you consider I only have 520 hours on the motor and I've had it for nearly 10 years, and the fact a new motor would be around 16 grand, $300 is a pretty cheap upgrade to make the motor truly bulletproof.  If anyone has any questions on this send me some mail and I'd be more than happy to help you out should you do the same thing to your motor.  OK, I didn't say I'd do it for you, but just "help you" with it!!              Sherm


Old Assembly Report:

I took the old Assembly apart and inspected it all, because that's just what I do!  The gears were in extremely good shape, so good in fact that it appeared there was no wear at all on them.  However, what I did find reinforced my decision to check this problem out and go to an upgraded part.  The Assembly was not spinning as freely as the new one was.  In other words, if you "spun" those two arms that are in the Assembly, they would spin around but then stop at a certain point.  The new Assembly when "spun", would just keep flying around in a circle, it moved very easily.  I took the shafts apart and exposed the bearing races, these are the smooth surfaces that the shaft rides on.  They did show some wear at the tops of them, but even with the race caps taken off, the shafts still "stuck" in a certain spot and, when both shafts  were put back in the Assembly without the race caps on and spun, it was even harder to spin them.  What does this mean?  Well, short of having some engineer looking at it I would have to say there has been some misalignment between the shafts and the bearing races.  What this has done is made the tolerances between the fiber gear and the metal gear less than they should be, and therefore binding.  Long story short I do believe there would have been a problem down the road with this Assembly.  How long it would have lasted is anyone's guess but, I don't have to worry about that now do I!!