77 Merc 850 - Water puddled on exhaust plate

[Bradmph]

The boat has not ran well, so I checked plugs and found tiny water droplets on plugs. Mostly on No.4 and just around the edge of the plug. I decided to remove powerhead to see if I can locate the problem. After removing the powerhead, I found water puddled in the exhaust plate in the driveshaft cavity. I included some photos of both the powerhead and exhaust plate sides. I need some good help on this one if anyone knows where it probably is coming from.

Comp Test:
1=115
2=120
3=115
4=120

The boat has only been hooked up to a hose so far because it would not idle for more than a minute and dies soon as it is put into gear when I went to the lake quite awhile ago. It takes a big squirt of fuel directly into carbs to start and then dies after it uses it up.

 

[chum1]

Re: 77 Merc 850 - Water puddled on exhaust plate

ahhh nice pics Bradmph,

Looks like you have some nice metal to work with, that powerhead looks like it has been removed in the not to distant past too.

have you been through the impeller waterpump already?

some possible sources of water leaks that i know of:

1) seals in lower crankcase cap

2) water jacket and exhaust plate on L/H side of engine

3) waterpump area on top of lower unit

The best way to fix an unknown motor from shade tree "i got some bailing twine that might work" thinking is to systematically go through each system.

download a manual so you know the specs and clearances

plan on replacing all gaskets,seals, hoses as you go, those things are over 30 years old if they haven't been refreshed.

if the stator/powerpack/trigger/rectifier are original assume they are shot they may be good but you have to prove it, the wires & insulation will probably be toast and are not worth messing with if you desire a reliable motor.

careful pulling the original steel bolts out of the aluminum case, i have about 18 helicoils in my old salty now.

ebay has been a real value on merc used parts for me theirs lots of them it just takes time to find.

It cost me about $900.00 in parts to get mine going really good (that is before i hit something and bent sh...t )

sure you could pick up another used engine for cheap but then you would have to dump another $900.00 into it and start all over so take your time and do it right the first time.

 

[coolguy147]

Re: 77 Merc 850 - Water puddled on exhaust plate

get some new gaskets. you don't want an exhaust leak! if you take the motor mounts apart make sure you seal the "U-cup seal" properly. motors mounts in good condition while you have the powerhead off.

my motor mounts started to show their wear after i got to running the motor on the boat.

900??? what??? i think ive probably put in less than 300 bucks to make my motor reliable???

 

[chum1]

Re: 77 Merc 850 - Water puddled on exhaust plate

yep about $900.00....taint cheap!, about $450.00 for sparky components from cdi, $120.00 for prop thats now a 2 1/2 blader, and the rest for a full water pump,gaskets, seals,paint, throttle/shift cable,etc......it adds up fast, runs very good though.

 

[Bradmph]

Re: 77 Merc 850 - Water puddled on exhaust plate

Well I found the issue on the water sitting in the shaft cavity. My mechanic is going to probably see my 850 mercury again and this time I hope he is sober. RRrrrrr!
The bottom end plate had a small crack on an edge though I gave my permission to put some cold weld glue on it and snap it back together. That part was fine and holding well. But, as I compared my 2 power heads between one another, I notice he did not put the seal on the end cap. Sheeesh! ya put your faith in a mechanic and darn, I am a trusting person that can overlook a simple mistake, but not this time. I am a bit angry and poop is going to roll up hill this time when I let him know what he did. I went to 2 mechanics to diagnose it for me and the first one was right on the money, the second one was still talking about a total rebuild as I was driving away. I wonder how it ended, lol. Sometimes you just have to find out for yourself who knows their stuff and who doesn't. I found out by getting my hands dirty and now I can change a power head like a Nascar pit crew. I am going to continue with the power head replacement that I was doing when I found the problem and run this used one for the rest of the good weather. Meanwhile I will dig into the first power head and make the repairs myself. I should have done that from the start if I would just stop underestimating my own mechanical abilities. (kicking myself).
Thanks all for responding, I appreciate all of you and I will always respond with my outcomes when I find my answers so all can get feedback from it.