Reply To: Power Head Cross Reference for 1958 Evinrude Fisherman 5516

[Don]

OK, if the gear lube was relatively clean and impeller was replaced, then there is no need to disassemble the gearcase for sure.

Sounds like the powerhead is definitely stiff for some reason.  Does it feel the same as it did before you disassembled it?  You mentioned the pistons seem to move up and down easily and are not obviously damaged.  Did it look as though the powerhead had been split apart before you disassembled it?  We definitely need to sort out this issue before you spend anymore time and money to rebuild it.  Frank has stayed awake thinking about this, so rest assured we will help you figure it out.

Let’s begin with some basic things, and please don’t be offended if I ask some obvious questions, we just have to start at the beginning.  The connecting rod caps are unique to each individual rod, so the rods will definitely bind if the caps have been inadvertently swapped between the two rods.  Furthermore, rod cap orientation is critical also, it will only fit properly when oriented correctly.  There are line up marks on the caps and rods, but they are not that easy to see unfortunately.  But, the rods will definitely bind if the caps are not oriented properly as well.

Frank mentioned a bent crank, surely possible.  So, we need to isolate the rods from the crank, reassembled the crankcase halves, then spin it over again.  Before we do that, I need to point out the two crankcase alignment taper/ dowel pins that help keep the crankcase halves aligned correctly.  These pins should have been driven out (before loosening the crankcase screws, driven out from the cylinder side towards the intake side).  During reassembly, the pins are reinstalled (from the intake side toward the cylinders once the main six crankcase screws have been lightly secured) before actually snugging up/torquing the screws.  This ensures the two halves are properly aligned.  It should also be mentioned that crankcase halves are unique pieces and can not be swapped between different powerheads, but this condition doesn’t seem likely here unless there was evidence the powerhead had been apart before you diassembled it .

So let’s do this slowly to help isolate the actual problem.  I guess I would start by driving the taper pins back out then just loosening the crankcase screws slightly to see if the engine frees up.  If it does, then this would indicate some sort of crankcase fit/alignment issue, or a possible bent crank.  If rotation is still stiff, then I would suspect a problem with rod cap fit/orientation.  Remove the front crankcase half, then try to rotate again.  If it is still stiff, we will move on to the rods.  First, check to see that the alignment marks on the rod halves are properly lined up.  If not, well this issue will be resolved with new rods.  If the alignment marks are properly oriented, then we will loosen one rod cap at a time and retest/rotate.  Loosen one rod cap, then try to rotate again.  If it frees up, then we have isolated that there is a fit issue.  If it is still stiff, then try loosening the other rod, a fit issue should be suspected  on that rod.  Perhaps there is a fit issue on both rods.  Again, there is no way of knowing if the rod caps have been swapped between rods, but you should be able to tell if cap orientation was messed up by looking at the line up marks and the two halves.

Finally, if nothing seems resolved by loosening the rod caps, then I would disconnect one rod at a time, push its piston out of the cylinder (please mark the pistons), then try to rotate.  Then remove the other piston and try to rotate again.  If nothing seems resolved, then we can suspect some sort of crank issue like Frank spoke of.  If rotation frees up with either one/both of the rods separated from the crank, then there is a rod fit issue, or perhaps a bent rod or binding piston.    At this point, I would reassemble the crankcase halves/taper pins with just the crank installed.  Does it spin freely with the crankcase screws lightly snugged up?  If so, try tightening/torquing them.  A bent crank, or crankcase alignment issues should be suspected if rotating the crank is difficult with the crankcase screwed tightened up.

Sorry, I realize words can be confusing, feel free to ask questions for clarification.  Nonetheless, we have to isolate the issue before you go ahead with this project.