1978 75 HP Chrysler outboard new piston

[charakel]

1978 75HP Chrysler outboard Model# 757H8D

Hello all. Well with the help of this group I have tore my motor apart and removed the bad piston. I have ordered my parts and should be coming today. When ordering I paid too much attention on the correct bore size than looks.. My question is my old piston is solid with no holes on the side, however the new piston that I ordered has 2 holes on the side of the piston??? What are the holes for? Will it work for me? Or should I just return it?? Thanks for all help!!

 

[charakel]

No Title

 

[Frank Acampora]

Well, your 75 should have a 3.3125 bore. I don't remember any of those skirt vented pistons being that bore. Also, the new piston has a semi-keystone top ring These rings do tend to occasionally catch in the exhaust ports and break. The holes in the side of the piston are vents for an older Chrysler 55, 60, 65 engine with a 3.375 bore, which had a packed block and no bypass covers. The manufacturer has simply not changed the tooling process. I have seen later Force 50s with these same pistons. Compare the wrist pin hole location and size.

If you have a choice, do not use the existing piston. All pistons I buy are Wiseco--a little more expensive but worth it in my opinion.

 

[charakel]

Thanks for the confirmation. I started a return and ordered the correct one. This group is a life saver!!!

 

[charakel]

Afternoon guys. All my correct rebuild parts should be here tomorrow. I have a pretty good idea on how to reassemble on all but the rod bearing halves. Is there a special trick? Do i use grease and put the bearings in the halves? It almost looks like the cage splits at a bearing hole, how do i line it up... Thanks

 

[Frank Acampora]

If you are using a stock piston with the press on wrist pin collars, you really need a press and a special tool to reassemble the small end of the con-rod. If you are using an after market piston with a slide-in wrist pin and circlip retainers it can be done by hand.

assuming you have the engine block apart: The big end of the con-rod is set on the crank. One bearing cage is set on the top of the crankpin. bearings are greased and inserted into the cage. The cage is "rolled" under the crankpin onto the big end of the rod. Repeat with the top cage and attach the big end rod cap. Bolts are torqued to 190 INCH pounds.

Caution. Install the rod with the correct orientation in the piston. Rod caps are not interchangeable and must go on the same rod. Additionally they must be installed the same way they were taken off. Because they are cracked cap rods, the caps can only go on one way. Before torqueing the cap screws. align the rod cap and with a pencil point or scribe, or even a small screwdriver, feel the ground flats to be certain the cap is aligned correctly. There should be no gap or catches. The pencil should glide over the break easily and smoothly.Before fully tightening the cap bolts, rotate the crankshaft several turns to be certain there is no binding. Do this again after torqueing the bolts.

 

[charakel]

I just having a hell of a time with parts. Got my new vertex piston today... poston pin will not work with stock piston pin bearing... wait on more parts.