MacGregorSailors.com

So - if there's a shear pin, would it be #14? They call it a clutch pin.

Check to see if the engine can be shifted between forward and reverse, the pin and the part it holds on the shaft is part of the shifting mechanism - it holds either gears 2 or 4 (forward and reverse) in contact with the pinion drive gear 3.
I do not see anything I identify as a shear pin although if pin 14 were bad, things would not work and you may experience loss of power (thus the question about shifting between F and R).
I spun the hub on my engine and had similar no-power results, in my case I could manage no more than 6 knots with my ETEC 60.
(This same event also resulted in a $2600 repair to the lower end of my ETEC 60, new propeller, prop shaft, all gears, and all bearings.)

BTW, I notice several bits of advise about only using premium gas. To my understanding, this may have been true 30 years or so ago but for a long time, Federal law in the USA has mandated that all grades of gas have the same level of detergent and similar additives. The only thing premium gas has is a higher octane rating - this does not have any performance differences except it is not as combustible as lower octane fuel from the point of view it resists pre-detonation longer. Unless the engine has a compression ratio and timing that requires premium to resist pre-detonation, using premium is a waste of money.

NavySailor wrote:So - if there's a shear pin, would it be #14? They call it a clutch pin.

If that pin sheared, it would cause the symptoms you cite, but a shear pin traditionally sits outside the gear case where it can be easily replaced. I happen to have been inside my Nissan 4HP case to replace ground up gears when I hit a wire fish bait mooring at speed. That pin (14) is holding the clutch onto the prop shaft. If it is the only thing that went, it's easy to replace.

So I opened up the lower part of my motor last night. First I drained the oil. About 3/4 of it was blackish. The other 1/4 was this nasty brown muck. Assuming outboard oil shouldn't do that? Your guess is as good as mine about when the oil was done last. Yuck.


Next I took the lower assembly off. Thankfully all the linkages and gears looked OK (at least to my unprofessional eye). I opened up the water pump and discovered my impeller looked like a badly mangled ferris wheel after a tornado ripped all the cars off of it!


All the debris from the impeller had built up in this little cavity below the impeller.


My question to you all is this - would this faulty impeller have kept the motor from producing thrust? Remember my prop was spinning, cooling water was coming out, but no thrust. (I'm surprised cooling water was coming out at all. Wow!)

Assuming that this is all that I need to fix it? http://www.boats.net/parts/detail/nissa ... 322-1.html

Bump... Anybody??

No, the water pump impeller failure will prevent the engine from operating within its normal range, but unless the engine is overheated, it has nothing to do with thrust from the prop. Some small OBs have a shear pin instead of spline for the prop, but yours appears to have thru-hub exhaust and a splined connection, so no shear pin.

If the engine runs full speed but you get no thrust, there's a mechanical disconnect somewhere between the engine crank shaft and the propeller, which includes the rubber connection inside the prop between the splined billet and the prop itself.

If the engine isn't getting up to full speed, it's fuel, or overheating, or ignition, or something like that relating to engine (rather than drivetrain) performance.

Which avenue to pursue depends on whether or not the engine can get to full speed, or close to it.

And you need new gear oil. And you possibly also have impeller bits in the engine cooling passages.

Thanks very much for the info. I thought the same but not knowing much about OBs was hoping there was something simple that I wasn't thinking of.

I'm going to replace the water pump and am hoping that when I reassemble the unit that it will work properly... maybe something wasn't connected properly before. The engine runs just fine and responds to the throttle.

When I connect the vertical driveshaft to the lower gear case, I can manually rotate it, and thus the propeller shaft in return. I can also manually rotate the propeller shaft and the vertical driveshaft rotates as well. I've inspected all the gear teeth and the linkages all appear to be ok.

I cannot figure out how to get the propeller shaft and related parts out of the lower unit. I've removed the propeller nut and propeller, but nothing else will come out. I don't see any other screws.

When you manually rotate the shafts, apply resistance to them at the same time (like a vice grip and a rag) to make sure there is no slipping, instead of just turning them. Then you can be certain they're solidly connecting.

From the diagramme it looks like one source of slippage could be between part 8 (what material is it made from?), which appears to engage the spline, and part 7 (prop) which appears to have a cone, or releasing taper that engages a mating face on 8.

Maybe the prop nut was not tight enough (?) or was bottomed out(?) before, if it relies on this tension for torque and shock absorption. That would give you the symptoms you're having (among other things).

Not to discourage you, but depending on how long there was water in the gear oil (that's what the brown “mousse” is, rust, probably the bottom layer) the bearings might be bad, or ready to fail. How “lucky” do you feel?

Spin the prop while applying hand thrust one way and then the other to see if you can feel any roughness in them, if you can't inspect them visually. That can also be an indication that the seal(s)also need(s) replacing; they're letting water in.

The parts diagramme really doesn't give enough detail to tell too much more. There are different ways the shaft could be contained, circlip or other retaining ring, or a threaded ring needing a pin spanner...? But it will have to withstand the thrust when in reverse.

Good luck!

BTW, I notice several bits of advise about only using premium gas. To my understanding, this may have been true 30 years or so ago but for a long time, Federal law in the USA has mandated that all grades of gas have the same level of detergent and similar additives. The only thing premium gas has is a higher octane rating - this does not have any performance differences except it is not as combustible as lower octane fuel from the point of view it resists pre-detonation longer. Unless the engine has a compression ratio and timing that requires premium to resist pre-detonation, using premium is a waste of money.

A very good question.

The higher octane rating of premium gas can come from the addition of ethanol (bad- the politician's choice) which has a high octane rating itself, or from other additives and ingredients (good- the chemist's choice), or a combination of both (meh)!

If the increased octane rating comes from the addition of ethanol, then as we all know or have discovered, the shelf life of the gasoline is shortened, because the mixture is inherently less stable. As gasoline ages many things happen to it, among them, the octane rating drops over time. Every engine has a design octane rating at which it performs best, and using fuel with a rating higher than this is certainly a waste of money, because the engine cannot take advantage of it (usually because its compression ratio is not high enough – and higher compression ratio mean higher efficiency- the compression ratio of autos has been escalating).

If you use gasoline with a lower rating than this, sophisticated engines can adapt to it (eg. knock sensors in the engine block, in early Corvettes, and modern engines, such as by retarding the ignition timing (in individual, or all cylinders), valve timing, valve lift, injector pulsing, etc) so that no engine damage is done, but at the cost of efficiency, performance, and fuel mileage.

If you go much lower than the design octane number of an engine that can't adapt, or go much lower than what it can adapt to, performance starts to suffer, and if the fuel octane rating drops too low you get catastrophic engine damage.

So the train of thought that leads to my recommendation of using premium gas in certain situations stems partly from the reduced shelf life that ethylated premium fuels have*. If the fuel in the tank starts at 93 octane it will last a longer period in storage (even with fuel stabilizer added) than fuel in the tank that starts out at 89 octane rating, before dropping to below acceptable levels. You are less likely to have starting troubles and/ or engine damage after a period of inactivity or storage.

If there is already questionable fuel in the tank that might have dropped to below what the engine requires, then mixing in high-octane premium will bring the octane rating of the mixed fuel to what the engine requires to run well. It's important to realize that burning fuel with too low an octane rating can destroy a small engine quickly, and adding higher-octane fuel minimizes the probability of this happening.

The octane demands of an engine can also go up whenever it is doing higher than normal work, such as when towing a heavy trailer over hilly terrain under high ambient temperature. So under situations like this a higher than usual octane fuel can be appropriate for an engine that would not normally otherwise require it.

Also note that the octane needs for an engine can increase as the engine ages. Contaminants, impurities from combustion by-products can build up in the top of the pistons and the combustion chamber, reducing the unswept volume and therefore increasing the compression ratio. Particularly noticeable in older cars that are well-maintained.

-B.

*note that there are other negative implications of ethanol in fuel, such as phase separation (water and ethanol “dropout”) which results in lowered octane in the remaining fuel. While not a panacea, mixing higher octane fuel into this fuel can raise the net octane rating to within acceptable limits to get you by.

ps. the easiest way to understand the effects of octane rating is to think of high octane fuel as pushing the top of the piston down the cylinder, such as with your hand, and low octane fuel as hitting the piston down the cylinder, such as with a hammer (ouch)! The higher the octane, the slower-burning the fuel is, and the more energy it can efficiently divert toward pushing, instead of hitting the piston.

seahouse wrote:When you manually rotate the shafts, apply resistance to them at the same time (like a vice grip and a rag) to make sure there is no slipping, instead of just turning them. Then you can be certain they're solidly connecting.

From the diagramme it looks like one source of slippage could be between part 8 (what material is it made from?), which appears to engage the spline, and part 7 (prop) which appears to have a cone, or releasing taper that engages a mating face on 8.

Maybe the prop nut was not tight enough (?) or was bottomed out(?) before, if it relies on this tension for torque and shock absorption. That would give you the symptoms you're having (among other things).

Not to discourage you, but depending on how long there was water in the gear oil (that's what the brown “mousse” is, rust, probably the bottom layer) the bearings might be bad, or ready to fail. How “lucky” do you feel?

Spin the prop while applying hand thrust one way and then the other to see if you can feel any roughness in them, if you can't inspect them visually. That can also be an indication that the seal(s)also need(s) replacing; they're letting water in.

The parts diagramme really doesn't give enough detail to tell too much more. There are different ways the shaft could be contained, circlip or other retaining ring, or a threaded ring needing a pin spanner...? But it will have to withstand the thrust when in reverse.

Good luck!

Thanks very much for the info - and I always feel lucky!

I'll try everything you suggested and let you know how it goes.

I'm working from memory but the gearbox comes apart by releasing the plate in front of the prop. Four screws I think

Your gearbox bearings will fine, but you probably need to change the seals since they are letting water into the gearbox

This link is much better than my memory

http://www.macgregorsailors.com/forum/v ... ar#p192124

If you are ordering and replacing the seals, I suggest replacing the bearings at the same time because you already have gone to the trouble to take the whole shebang apart, so most of the labour is already done, and bearings are cheap.

The bearings will be available from the same place the seals (and gaskets?) come from, so the ordering, handling, your driving (and shipping if applicable) etc. time and costs will be little more if all done at the same time.

It is also very difficult to judge the exact level of degradation from wear, flaking, spalling, or pitting of the old bearings without a very thorough cleaning and close inspection. The brown colour of the oil the bearings were immersed in comes from the presence of iron oxide, or rust (before that, it was the colour of mousse), and iron oxide is used in industry as an abrasive! (crocus cloth).

And all assuming that the origin of the rust was not from the bearings themselves ! (Yes, a layer can come off bearing contact surfaces and expose the more rust-prone ferrous metal below).

But, of course, it's your decision, and you know how much longer you expect to have the engine, and the level of inconvenience another breakdown might be.

Mod note - moved to REPAIRS forum

seahouse wrote:

BTW, I notice several bits of advise about only using premium gas. To my understanding, this may have been true 30 years or so ago but for a long time, Federal law in the USA has mandated that all grades of gas have the same level of detergent and similar additives. The only thing premium gas has is a higher octane rating - this does not have any performance differences except it is not as combustible as lower octane fuel from the point of view it resists pre-detonation longer. Unless the engine has a compression ratio and timing that requires premium to resist pre-detonation, using premium is a waste of money.

A very good question.

The higher octane rating of premium gas can come from the addition of ethanol (bad- the politician's choice) which has a high octane rating itself, or from other additives and ingredients (good- the chemist's choice), or a combination of both (meh)!
-
-
-
-

Interesting - I never asked a question

Interesting - I never asked a question

Either A)

The question was implied by the apparent ambiguity of the statement, which the answer addresses. The quality of being "good" is imparted to the question by the somewhat arcane nature of the information in the answer. I think there might be others on the forum who are curious about the same topic, particularly since some have experienced engine problems that are low octane related.

Or B)

This is Jeopardy and I should have posed the answer in the form of a question, so that the original statement did not need to be a question at all.
- B.