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Repurpose your head bolts, and replace at least the rod bolts.
If you weigh the rods and pistons separate, you'll likely build a better balanced engine. The last one I built had 3 different brands of pistons in it, and worked out pretty good, as I had rods that were all different weights. I think I got each assembly within a couple grams, if I would have not known, I could have been 20++ grams off.
I also did this on my new 200 build. Weighed everything and match light pistons with heavier rods.
Does the factory do this with it's ordinary fish motors? Talking simple matching, not shaving metal...
-Peter
Couldn't tell ya, as I've never weighed the carnage, but can say,.. Merc could of done a better job selecting a weight matched set of rods. The factory pistons were real close in weight.
Fascinating, for a motor that is meant to run 6000 rpm all day long in box stock form.Quote:
Originally Posted by OnPad
-Peter
I just weighed all the pistons and rods. The three good pistons, I am not separating from the rods. All 3 of the piston rod/combinations weigh within 3 grams of each other. The 3 loose rods I am reusing weigh within 2 grams of each other. The three new pistons weigh within 4 grams of each other. That is not a big difference in weight. 1 gram is 5 pieces of Apple Jacks cereal. Attachment 527558
You got a good one. They ain't all like that.
I have been thinking about how and why this motor blew up the way it did. 3 pistons disintegrated pretty badly. 3 pistons are perfect, and I am reusing them. There are no signs of overheating or lack of lubrication. I think it had to be an ignition problem. It has the 1st generation CDM ignition where all the modules and switch boxes are built into one controller. I would hate to build this motor just to have a bad ignition controller blow it up again. I think I am going to switch the entire ignition system back to the older CD ignition. I have a complete ignition system with the flywheel and all the mounting brackets to switch it over. The block has the correct bosses to mount the ignition brackets. The coil bracket uses different bosses on the exhaust cover. But I took the exhaust cover from the 150. I can use that one. It is the same on the inside as the 200. That way I can disconnect the rev limiter/ Idle stabilizer and not worry about it.
now ya gettin' tha idea... tha 'lectronic junk puts a limit on all things electric/performance wise on these motors.. but that may be a good thing for tha "normal" boat guy.............. :reddevil:Quote:
Originally Posted by skialot2
also merc don't weigh nothin'.. think tha suppliers have tolerances they have ta meet so no tellin' what ya get as for tha "balancing" on tha parts...
I have seen massive differences in rod weights all in the same motor. Merc weighs nothing nor does any other "production" company.
Rock
I just weighed another full set of loose rods. There is a 15 gram difference between the lightest and heaviest rod.
I don't think it is uncommon to see up to a 30 gram difference in rods that come out of a factory built engine.
Definitely, I saw similar results when weighing mine.Quote:
Originally Posted by OnPad
I just weighed another set of rods that came out of the 1998 150 I took the ignition from. 5 out of 6 were within 4 grams of each other, 1 was 8 grams lighter than the lightest of the 5. 12 grams from the lightest to the heaviest.
I also put my new pistons on the rods and weighed all the assembly's. Even with 3 oversize pistons, the difference between the lightest and heaviest assembly is 4 grams even. I say this is going to be a balanced motor.
I started going through all the parts for this motor. Everything is very dirty. It must have been stored for a while before he gave it away. In with all the parts I found 2 new thermostats still in the bags. Along with a new poppet repair kit and he already bought a new head to replace the damaged one. Unfortunately, I found some mysterious damage to a reed. The reed stop is folded back on itself flat. Attachment 527887
I don't know how, but it must have been damaged when it was assembled originally. There is a very light mark in the case half where it got pinched. I don't see anything wrong with the reed itself. Anyone got a reed stop I can have?