Mercury 850 Engine Rebuild Planning Stages

[wguttrid]

Hey guys planning on rebuilding engine during the off season and just researching the cheapest parts and kits and was wondering what the engine guys here would recommended I clean up and replace.

The engine I have is a Merc 850, compression is reading 140 +/-3 on all cylinders, have a newer lower unit installed on it that holds good pressure for 35 minutes.

What are some thoughts on items I should look at during the off season. Not looking at spending a fortune on it but at the same time not looking to cheap out.

 

[wguttrid]

Re: Mercury 850 Engine Rebuild Planning Stages

Also it is either a 73-74 and is not in bad shape but it is showing its age.

 

[buddyp]

Re: Mercury 850 Engine Rebuild Planning Stages

Why rebuild it does it run ok...comp looks good ...did you do a leak down to see how it is sealing?

 

[Faztbullet]

Re: Mercury 850 Engine Rebuild Planning Stages

If your going to the trouble of tearing it down, do the full rebuild. I have not seen but several inlines that did not need boring do to side thrust wear around ports. If it was mine I would:
1) bore .015 or .020
2) restricter mod
3) replace reed blocks with late models (less wear on labryth seals)
4) full carb,fuel pump and hose replacement/repair/rebuild
5) replace/repair any bad wiring internally and check/repair stator
6) full water pump kit and lower unit pressure testing/repair