1971 Merc.800 any good pointers

Is there an easy way to see if the bottom crank case seal is still Okay.I would also just out of curiosity like to know if it is normal for these motors to rattle alot (sounds like a bucket of bolts flying around).Dont get me wrong once you give it some fuel it sounds pretty sound.I realize its a 40 year old motor.I would like to give you folks here a run down of what I have done to get this running(but just cant get it to perform according to specs.).
1) Brand new switchbox 332-2986A27
2) Rebuilt 85hp carbs (done several times) (one thing I have noticed top carb is leaking a little where the linkage goes for the bottom carb).
3) Newer Trigger/Distributor New Distributor cap
4) New spark plug wires,new spark plugs NGK BUHW
5) new fuel pump Diaghram/gaskets
6) new fuel hoses all the way to the tank
7) Radioshack Recitifier
8)Newer lower unit 80's model with a 2.0 gear ratio had to drop down to a 13 1/4 13 pitch to accomadate the original 2.3 gear ratio
9)New impeller
10)Stator is in good shape good charging battery.
11) Set Timing Link/Synch.
12) At one time it would turn 5000 rpm and now I cant get 4600 rpm and would cruise 35 MPH with GPS and now down to 29 MPH GPS. Same boat 1972 15 foot trihull Starcraft.
13) Compression is at 1)115 2)125 3)125 4)125
Last time out I had to pump the bulb once and awhile to keep WOT.I am really thinking I am missing something here I am starting have sleepless nights on what else to fix LOL.
Any great Ideas before I start selling parts
Also new fuel tank..

Re: 1971 Merc.800 any good pointers

if its rattling that bad you may have lost some needle bearings. i would tear it down for a rebuild and you also have low compression on one cylinder

Re: 1971 Merc.800 any good pointers

It shouldn't rattle. Typical two-cycle rattles would be piston skirt to cylinder slapping at idle.

If the compression is good, you might as well run it.

Re: 1971 Merc.800 any good pointers

you may try to hook a timing light one spark plug at a time and see if its dropping a spark on one plug next time your out on the lake, lower end seals are fairly easy to change once you pull the power head and remove bottom cap (may need a puller but you can pull it without if your careful) requires one oring and two seals, water leaking in on bottom cyl's is usually a sign of bad lower seals.


here is a vid of my engine rattling.

Re: 1971 Merc.800 any good pointers

http://www.youtube.com/watch?v=9QsoOl9ZIPI&feature=related maybe this is what your talking about? i don't think that it's this bad though

btw in the video your motor sounds great. i read somewherre that merc tend to be a bit noisey at idle.