1982 15hp Johnson

Need some help. I have a 1982 15 horse Johnson that runs, but when I accereralte it stalls. The model number is J15RCNC. I thought it might be the prop. My thinking was maybe it hit a rock or something and broke the pin. But I found out it doesn't have a pin. I'm thinking there is some other part that protects the propeller shaft when this happens. I can't seem to find out what that is. I've looked in the repair maunal and it seems like it might be a thrust washer but I'm not sure. I don't even know what the thrust washer is for. I have done a compression check and one cylinder is 60psi and the other one is 70psi. I don't know if this is good or bad. I also checked the spark plugs, they look good to me. I have determined that there is a spark on both cylinders that jump a gap of 5/16". I tested the maunal fuel pump when the engine is running it doesn't change the performance of the engine, don't know if this is good or bad either. I don't know where to turn next. Any suggestions would be appreciated.

You may want to do the carb on it and be sure to check the high speed jet.

kimcrwbr1 said:

Pull the head your a little over 10% difference between cylinders. Inspect the cylinder walls especially around the exhaust ports. If no scoring is present get a new head gasket, lightly surface the head with 200grit on a glass table just enough to where it all shines the same in a figure 8 pattern. 70psi is ok for a pull start motor as long as it is even between cylinders. confirm compression is even and do a cylinder drop test. In a barrel of water at an idle pull a spark plug wire and put it back on. The engine should respond the same on either cylinder if it stalls the other cylinder is not firing. It could be a fuel supply issue but fix the know issue first the compression must be even to run good.

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Thanks for the reply, kimcrwbr1. I will order the head gasket and pull the head. If there is scoring in the cylinder how do I fix that? I have a plastic garbage can that I was planning on using to run the engine, can I leave the prop on to do the cylinder drop test? I am planning on testing the fuel pump before I order the head gasket incase I need a new one. Your reply would be appreciated.

It depends on your budget / mad money.----A fuel pump repair kit is much cheaper , and yes they are available.--Same pump was used for many models over many years.