A sliding clutch dog strip that’s flexible around a propeller shaft is the mechanism of a clutch dog. It has recesses on each end face.
The clutch, once engaged, reduces friction, slip and heat. It also provides a torque capacity similar to friction clutch but is/ cost-effective.
In this article, the symptoms of a bad crutch dog and ways of troubleshooting are described in detail. Read till the end to find out!
What Sign You Should Look for to Detect a Bad Clutch Dog?
A bad clutch dog can often be confusing. Clear signs do not often present themselves distinctively.
But the most distinguishable sign for a bad clutch dog is difficulty in shifting gears. Both forward and reverse. The engine seems to slip or bounce too in high speed or during acceleration.
What Are the Symptoms of a Bad Clutch Dog?
The symptoms of a bad clutch dog are given below:
The engine motor kicking means violent jerking. It may also jump slightly up and down its mount. You may notice that the motor clunks against the transom while trying to reach the WOT (Wide Open Throttle). It revs up and catches again.
You may notice this happening when you run the engine for too long. Way longer than regular runs.
It may feel like the engine actually sped up a bit while kicking. You may notice the jerkings happening in between every 10-120 seconds. This happens frequently as more there is more throttle.
Moreover, if you troubleshoot but the problem persists, then it is a symptom of a bad clutch dog. Troubleshooting may include filling up the tank with fuel and checking the cylinders to be normal.
Jumping Out of Gear
The clutch dog is usually splined to the prop shaft. This is seen in OMC manual shift outboard engines.
From the dog, a minimum of two lobes protrudes at both ends that face both the forward and reverse gears. These two gears also have built-in lobes in their central position.
The gears spin constantly when the engine runs in neutral. This happens through the driveshaft that is directly connected to the powerhead crankshaft. However, the propeller doesn’t turn as the dog is centered between two gears and its lobes don’t touch either of the gear lobes.
The shift linkages force the dog and lobes to engage when the unit is put into gear.
The gear lobes grab the dog and the splining of the dog to the shaft turns the propeller.
Dogs that are installed in one direction can immediately jump out of gear when reversed, despite being new. You can hear the clutch dogs clattering before going into gear.
When the dogs get worn out or damaged, it frequently jumps out of the gear because of losing shape and functionality. This is because the sharp edges of intricate machinery wear down. And the more you throttle up, the more the kicking increases.
Clutch tends to jump out more with load. Shifting the gears is also difficult.
But remember gear shifting should always take place in lower RPMs.
Do not take the RPMs to as high as 600 and then complain that your gear is bad because it jerks.
Evidence of Slipping of GearBox
The clutch dog slips, that is the engine slips when at high speed.
Mark a line across the end of the shaft and the prop. Then take the boat out for a spin. When you come back, check the lines.
If the lines do not align, then the hub is slipping.
Problem While Acceleration
With the case of a bad clutch dog, speed becomes an issue. As said before, speed seems to increase while the gearbox slips.
But when you start increasing the speed, the engine may seem to be hesitating to take up to that speed.
A simple yet effective test to check for a bad clutch dog is the torque test. It is as follows-
Between the prop and anti vent plate, put a 2×4 while the gear selection is at F. With a torque wrench, get on the flywheel nut. Then in the CW direction, apply around 50-60 ft-lbs of torque on the nut.
The clutch dog will be able to take this amount of torque if it is in perfect shape. If it is not, then you will see some movement.
The ideal prop nut torque is 55 ft-lbs and for flywheel nut, it is 120 ft-lbs. So this test is not going to loosen up anything.
How Should You React If You Detect a Bad Clutch Dog?
You can try to fix the clutch dog yourself.
As discussed, a bad clutch dog jumps out of gear because of the rounded edges of its pawl.
So you can just get rid of the worn-out ramps in the mating side of the pawl. You can manually try filing the perpendicular edges of the pawl.
But do remember not to overdo it. Because the engine requires a certain thickness of the pawl to feed power through them.
You may also try flipping the clutch dog around the other side. But it’s probably best if you get rid of the ramp and mate the gear with the forward gear.
Moreover, when you detect a bad dog clutch, be careful about shifting gears at a low speed when boating. Fix or replace it as soon as possible. Notice any bad cables and replace them as well.
Is Replacing a Bad Clutch Dog Typically Expensive?
Replacing a bad cutch dog holds expenses starting from the cost of the clutch dog, a whole gear set and services.
People seem to be tending towards $110 bad dogs, found both offline and in stores. They also prefer gearsets that cost around $300.
The Mercury Mariner Force Clutch Dog 11062 52-823174T, 78959, 823174, 18-2237 costs $69.66 on eBay. This quite a proper clutch dog.
As gears need replacement too when the clutch dog goes bad, you need to buy them too. Replacing gears can cost around $150 for both forward and reverse ones. This is in the case of one set of gears
For more than one set of gears, a whopping $600-800 easily slips. So, replacing more than one gear set is a bit expensive.
The cost of the course varies according to the model of your boat.
How Often Should You Inspect or Service the Clutch Dog?
The shift system should be regularly checked and adjusted. This regularity can be once a week or once 10 days.
Shifting fork wear should also be checked regularly.
Clutch dogs can last from 10,000 – 30,000 miles. It is advised to replace clutch dogs after every 60,000 miles of usage.
Clutch dog replacement can be quite expensive, so prevention is the key here.
Shifting gears need to be done gently and at low RPMs. Moreover, regular inspection of worn-out cables is also necessary.
Replacement of clutch after the advised duration is necessary. Moreover, fixing manually, the clutch dog should be tread with care as well.
With that saying, clutch dogs make your sailing easy, so a little bit of awareness can save you a lot of bucks!