wmk0002
Well-known member
I have a 1967 Evinrude Sportwin 9.5 hp which I believe has an exhaust leak and I was looking for some help on the matter. This motor is new to me and this is my first time working on this particular model. I have a running post on the matter on another forum but it has fallen through the cracks to the knowledgeable members. I was thinking plenty of guys on this board would have the same model motor due to it's suitability for small jon boats. Any help is appreciated.
What I know about the motor:
The motor has 65 psi in each cylinder. New and properly gapped spark plugs. I cleaned and gapped the points and the spark jumps well over a 1/4" gap. The LU is good and has fresh oil. The impeller is new and it is pumping good water. The thermostat is functioning per a bench, err... stovetop, test. I cleaned and rebuilt the carb. New fuel line from fuel pump to carb.
How it performs:
The motor starts and runs well in a barrel or on a boat with the cowl off. I water tested it last weekend and, with the cowl off and low speed needle at about 1 1/2 turns out, it ran about 15 mph and was turning about 4800 rpms (WOT range is 4000-5000) so it seems that it is running like it should.
When I put the cowl on it would not idle down very low without dying. It accelerated pretty good though and did push the boat about 13 mph but it was only turning about 4000 rpms and it seemed to fluctuate a little more than it should. The farther in I turned the low speed needle, the better and faster it ran. With the low speed needle all the way in, it was running about 14 mph and turning maybe 4400 rpms. For most motors, any less than 3/4 turn out is too lean so I only did that briefly.
Questions:
Am I correct to believe that this is likely an exhaust leak? A previous owner had drilled a bunch of holes in the cowl directly above the carb to likely try correct the same issue. But there also appears to be ample ventilation spots for fresh air to come in, primarily around the sides of the front plate where the pull starter handle, choke, and low speed knob is. This leads me to believe that it is getting fresh air but that it also has contamination from exhaust gasses present.
If it is a leak, I am aware of the 4 potential locations. So far I checked the seal on top of the water pump which looked good and attempted to check the shift rod boot. I say attempted because I couldn't figure out how to get the retaining plate off as the bend in the water tube prevents it from sliding down and off the shift rod. Would this require powerhead removal? If so, I will just go for it and replace it plus that other large main seal between the powerhead and case while at it. I also haven't check the overboard water tube yet, which is the easiest, so I will do that in the meantime.
Thanks in advance for any advice you guys can give!
What I know about the motor:
The motor has 65 psi in each cylinder. New and properly gapped spark plugs. I cleaned and gapped the points and the spark jumps well over a 1/4" gap. The LU is good and has fresh oil. The impeller is new and it is pumping good water. The thermostat is functioning per a bench, err... stovetop, test. I cleaned and rebuilt the carb. New fuel line from fuel pump to carb.
How it performs:
The motor starts and runs well in a barrel or on a boat with the cowl off. I water tested it last weekend and, with the cowl off and low speed needle at about 1 1/2 turns out, it ran about 15 mph and was turning about 4800 rpms (WOT range is 4000-5000) so it seems that it is running like it should.
When I put the cowl on it would not idle down very low without dying. It accelerated pretty good though and did push the boat about 13 mph but it was only turning about 4000 rpms and it seemed to fluctuate a little more than it should. The farther in I turned the low speed needle, the better and faster it ran. With the low speed needle all the way in, it was running about 14 mph and turning maybe 4400 rpms. For most motors, any less than 3/4 turn out is too lean so I only did that briefly.
Questions:
Am I correct to believe that this is likely an exhaust leak? A previous owner had drilled a bunch of holes in the cowl directly above the carb to likely try correct the same issue. But there also appears to be ample ventilation spots for fresh air to come in, primarily around the sides of the front plate where the pull starter handle, choke, and low speed knob is. This leads me to believe that it is getting fresh air but that it also has contamination from exhaust gasses present.
If it is a leak, I am aware of the 4 potential locations. So far I checked the seal on top of the water pump which looked good and attempted to check the shift rod boot. I say attempted because I couldn't figure out how to get the retaining plate off as the bend in the water tube prevents it from sliding down and off the shift rod. Would this require powerhead removal? If so, I will just go for it and replace it plus that other large main seal between the powerhead and case while at it. I also haven't check the overboard water tube yet, which is the easiest, so I will do that in the meantime.
Thanks in advance for any advice you guys can give!
