I am not an engine guru, but I have met some model boaters and manufacturers that really know their way around an engine. I paid attention to what they had to say. Your engine will give you many years of service if you take the time to maintain it.
Many model boaters don't know some simple engine maintenance, such as replacing the crankshaft bearings. It is not difficult. Different boaters have different thoughts as to the best way to remove the old bearings and install new bearings. This is how I do it.
First disassemble the engine. If the engine uses needle bearings on the crankpin, count how many there are so you will replace the correct number of needles. When the engine is disassembled down to just the crankcase, crankshaft and bearings, I put it into a toaster oven at 350 degrees for 20 to 30 miniutes.
Many people heat their crankcase with a torch. This is fine if you know what your are doing. It is easy to heat the crankcase unevenly which can make the crankcase warp a tiny bit. Heating in an oven, heats the parts evenly. Never exceed 400 degrees F as a lot of aluminums begin moving around at 400 degrees F. So much depends on the what the manufacturer uses and how much silicon is in the aluminum itself.
After taking the crankcase out of the oven, the bearings normally fall out. If they do not, put them back in the oven for another 10 to 15 minutes. If the bearings still refuse to fall out. I rap the large end of the crankcase against a piece of wood. The big bearing should just pop out. If the small bearing does not want to fall out, I use a wooden dowl to push the bearing out. Normally with a rubber or plastic mallet. Remember that the crankcase is still very hot. I use heavy leather gloves to hold the hot crankcase.
Then let the crankcase cool as it is quite hot coming out of the oven. When it is cool, I use a toothbrush and lacquer thinner to clean the crankcase inside and outside. When it is clean and dry, I put it back into the oven at 200 to 250 degrees F for 20 to 30 minutes. The aluminum crankcase will expand evenly.
Now, it is time to install the new bearings. Again other people have their own ways of installing the new bearings. I first install the small bearing, using an arbor press. Some people use a vise, but I think it is too easy to damage the engine that way. Make certain that the small bearing is fully inserted. The K21 front bearing actually is inserted further into the crankcase than the edge of the crankcase.
Next, I press the big bearing into place on the crankshaft. Put a film of oil onto the crankshaft and slide the crankshaft into place, extending through the front bearing. Put the flywheel collet and flywheel onto the crankshaft and draw it tight. You can look through the crankcase to see if the big bearing has been drawn into place. If it isn't, I use my arbor press and a socket to press the big bearing fully into place. The crankshaft pin should be lined up in the center.
To make sure that the new bearings are perfectly aligned on the crankshaft, I hold the flywheel, and only the flywheel. Then using a wooden or plastic mallet, I strike the cable nut squarely in line with the crank shaft two or three times. The crankshaft should spin freely. Then I pour oil into the crankcase around the big bearing.
Holding the crankcase upright, the crankshaft should spin freely and always stop with the counter weight at the crankcase bottom.
If you are uncomfortable replacing the bearings, don't keep running with worn bearings. Your engine will not perform properly. There are several people on this forum that do work for other boaters, including replacing the bearings. Don't hesitate to contact them to get your engine back to peak performance.
Many model boaters don't know some simple engine maintenance, such as replacing the crankshaft bearings. It is not difficult. Different boaters have different thoughts as to the best way to remove the old bearings and install new bearings. This is how I do it.
First disassemble the engine. If the engine uses needle bearings on the crankpin, count how many there are so you will replace the correct number of needles. When the engine is disassembled down to just the crankcase, crankshaft and bearings, I put it into a toaster oven at 350 degrees for 20 to 30 miniutes.
Many people heat their crankcase with a torch. This is fine if you know what your are doing. It is easy to heat the crankcase unevenly which can make the crankcase warp a tiny bit. Heating in an oven, heats the parts evenly. Never exceed 400 degrees F as a lot of aluminums begin moving around at 400 degrees F. So much depends on the what the manufacturer uses and how much silicon is in the aluminum itself.
After taking the crankcase out of the oven, the bearings normally fall out. If they do not, put them back in the oven for another 10 to 15 minutes. If the bearings still refuse to fall out. I rap the large end of the crankcase against a piece of wood. The big bearing should just pop out. If the small bearing does not want to fall out, I use a wooden dowl to push the bearing out. Normally with a rubber or plastic mallet. Remember that the crankcase is still very hot. I use heavy leather gloves to hold the hot crankcase.
Then let the crankcase cool as it is quite hot coming out of the oven. When it is cool, I use a toothbrush and lacquer thinner to clean the crankcase inside and outside. When it is clean and dry, I put it back into the oven at 200 to 250 degrees F for 20 to 30 minutes. The aluminum crankcase will expand evenly.
Now, it is time to install the new bearings. Again other people have their own ways of installing the new bearings. I first install the small bearing, using an arbor press. Some people use a vise, but I think it is too easy to damage the engine that way. Make certain that the small bearing is fully inserted. The K21 front bearing actually is inserted further into the crankcase than the edge of the crankcase.
Next, I press the big bearing into place on the crankshaft. Put a film of oil onto the crankshaft and slide the crankshaft into place, extending through the front bearing. Put the flywheel collet and flywheel onto the crankshaft and draw it tight. You can look through the crankcase to see if the big bearing has been drawn into place. If it isn't, I use my arbor press and a socket to press the big bearing fully into place. The crankshaft pin should be lined up in the center.
To make sure that the new bearings are perfectly aligned on the crankshaft, I hold the flywheel, and only the flywheel. Then using a wooden or plastic mallet, I strike the cable nut squarely in line with the crank shaft two or three times. The crankshaft should spin freely. Then I pour oil into the crankcase around the big bearing.
Holding the crankcase upright, the crankshaft should spin freely and always stop with the counter weight at the crankcase bottom.
If you are uncomfortable replacing the bearings, don't keep running with worn bearings. Your engine will not perform properly. There are several people on this forum that do work for other boaters, including replacing the bearings. Don't hesitate to contact them to get your engine back to peak performance.
