1st boat 73 merc 850 wont rev.

[Ghost1958]

The top seal has to be replaced or the cylinder will run lean because there won't be enough pressure or suction to feed it; should be fixed before anymore running and what about the lower seals? You're going to be jury rigging this motor for however long it lasts and a lean piston won't last long. I bought an 850 and took it apart before I used it to check on all the seals bearings etc. it's been running hard for 6 summers and I get 8 mpg.
The seals can be replaced without opening the crankcase - seals are cheap and easy to replace.

I May have used the wrong term when I said leaking.

Its not actually leaking anything, no oil film no drips motor is clean enough to eat off of.

The mechanic sprayed I think starting fluid or the like up under the Orange I guess fly wheel on top while the motor was idleing on muffs. It sped up for a few seconds then slowed down again.
He said its losing enough vacuum that it can't operate the diaphragm on the pump to keep up at WOT.
He didn't believe the bottom seals were bad or leaking at all.

The seal itself is about ten bucks so that's no big thing. And I don't intend to run it a long time before changing it. Maybe a month. Couple of planned fishing trips at the local lake.


In just going on what he said. That as long as it wasn't showing any visual signs of actually leaking it wouldn't hurt it to run on a electric pump.
Is he wrong about that???
As far as the pump filter conversion I intended to do that anyway with a 3 low auto cut off at 5 psi Honda civic pump I have,,even when replacing the seals.

 

[Chris1956]

The crankshaft seals seal the fuel mixture in the crankcase, allowing efficient transfer to the combustion chamber. If the seal leaks, the cylinder will miss. When the mechanic sprayed the top seal, that cylinder started running.

You need to replace that seal. Also replace the oring that seals the end cap and check the bearing for wear.

Also, clean the brass fitting and check the hose, that allows lubricating oil to the bearing.

 

[Chris1956]

One more thing. The mechanical fuel pumps on that motor are perfectly adequate. An electric fuel pump is a real fire hazard. IMO, you will come out way ahead if you spend the money now to replace the seal and rebuild the fuel pumps.

 

[Ghost1958]

One more thing. The mechanical fuel pumps on that motor are perfectly adequate. An electric fuel pump is a real fire hazard. IMO, you will come out way ahead if you spend the money now to replace the seal and rebuild the fuel pumps.

Ok. I'll get him order the seal and pump diaphragm kit.

He may toss them in it for nothing or little labor.

Question. Folks keep saying " fuel pumps" plural.
I can only find one. Line runs from bulb to pump to filter to carbs.. I can see no other pump in the circuit.

Also just curious why an electric fuel pump would be a fire hazard if wired to stop if the motor dies like on a Goldwing?? Fuel flow would be stopped either way.

Not arguing , just trying to learn.

 

[merc850]

He means the factory engineered pumps are fine; they used to race Mercs always with factory pumps and won a hell of a lot of races. on that motor there's only one.

 

[Chris1956]

Gee, my 1973 Merc 850 had dual triangular fuel pumps, and a round-robin fuel line to feed both carbs. I am surprised they also came with one fuel pump.

Ghost, The fire hazard aspect of an electric fuel pump occurs if the motor stalls, and there is a leak in the fuel line/carbs etc. The boat would fill up with fuel. You would need some kind of safety relay to stop the electric fuel pump, when the motor stalls.

4 cycle motors can wire the oil pressure switch to the fuel pump. No oil pressure means the motor has stalled and the fuel pump can be turned off.

2 cycle motors cannot do that, and usually use the charging system to drive the fuel pump relay.

 

[Ghost1958]

Gee, my 1973 Merc 850 had dual triangular fuel pumps, and a round-robin fuel line to feed both carbs. I am surprised they also came with one fuel pump.

Ghost, The fire hazard aspect of an electric fuel pump occurs if the motor stalls, and there is a leak in the fuel line/carbs etc. The boat would fill up with fuel. You would need some kind of safety relay to stop the electric fuel pump, when the motor stalls.

4 cycle motors can wire the oil pressure switch to the fuel pump. No oil pressure means the motor has stalled and the fuel pump can be turned off.

2 cycle motors cannot do that, and usually use the charging system to drive the fuel pump relay.

That's how it's set up. Engine dies pump stops.
Its temporary anyway until we can figure out what's going on.
Had boat out today. Never really got away from the dock.

But I think I know why but not how it's occurring.
The last time it WOT for about a half mile was the day after I was messing with it. That day I took off the distributor cap and it had what looked like oil in it.

I wiped that out not thinking much of it. Next day it ran WOT for a good ways then bogged again.

From then it gradually got worse until today it wouldn't take throttle or idle in gear again.

And that oily stuff is inside the distributer again.

I know there are two grease fittings on the shaft. Is there a grease seal under them that could go bad and let melted grease in the distributer cap??

Wrong type grease??

Where could that oilly stuff come from to get INSIDE the distributer cap?????

 

[Chris1956]

The grease fittings should lube the distributor shaft in its housing and external linkage.

I am at a loss to help with the oily stuff that drips into the cap. It makes sense to remove the timing belt and make sure the distributor turns freely. Maybe some friction in the distributor bearings causes heat to melt the existing old dried grease around the distributor shaft? It is a guess.

 

[Ghost1958]

The grease fittings should lube the distributor shaft in its housing and external linkage.

I am at a loss to help with the oily stuff that drips into the cap. It makes sense to remove the timing belt and make sure the distributor turns freely. Maybe some friction in the distributor bearings causes heat to melt the existing old dried grease around the distributor shaft? It is a guess.

I'm almost tempted to say it's thinned out old axle grease. It has that color smell and feel. (I don't know nothin about boats but old farm boy here and seen and smelled a LOT of plain old grease.
I'm assuming it should be some type of marine grease??

 

[merc850]

There are 2 bearings in the distributor housing that are sealed - permanently lube ones 45 yrs ago, so maybe the bottom one is leaking (Nr.22 in diagram) if this is the case the bearing will seize and and the timing belt will break.

 

[Ghost1958]

There are 2 bearings in the distributor housing that are sealed - permanently lube ones 45 yrs ago, so maybe the bottom one is leaking (Nr.22 in diagram) if this is the case the bearing will seize and and the timing belt will break.

I'm guessing Replacing that bearing will require taking off the whole top of the motor.

I couldnt be lucky enough it can be got at from the bottom.

I've learned two things since getting this boat for certain

Don't matter if the seller runs you all over the lake and it runs perfect , you can still get ruined buying a boat.

And to listen when my brother in law says never buy a Mercury unless you know a Mercury mechanic.

I guess I should have expected to have to rebuild the whole motor but it ran perfectly and nothing wrong with it.
I signed the title and it starts falling apart.

The boat itself is nice though.

Just need a motor I can't afford for it.

Thanks for the help. It is very much appreciated.

 

[Chris1956]

Well, I think your brother shares a viewpoint with a lot of folks, just not me. Mercs are just as good as any other american production motor. Different models and years vary in quality. Your Merc is an excellent motor, for it's time. When it was new it was superior to many other equivalent makes, IMO.

Let's focus on the issue. Spin the distributor shaft and see if she spins freely. If not, you will need to pull the distributor off and replace the bearings. It is not a big or tough job, but you will need to read the procedure closely, as it is not straightforward. The dist. rotor is not removeable and will easily break. Treat it like glass, or pay the $200 to replace it.

 

[Ghost1958]

Well, I think your brother shares a viewpoint with a lot of folks, just not me. Mercs are just as good as any other american production motor. Different models and years vary in quality. Your Merc is an excellent motor, for it's time. When it was new it was superior to many other equivalent makes, IMO.

Let's focus on the issue. Spin the distributor shaft and see if she spins freely. If not, you will need to pull the distributor off and replace the bearings. It is not a big or tough job, but you will need to read the procedure closely, as it is not straightforward. The dist. rotor is not removeable and will easily break. Treat it like glass, or pay the $200 to replace it.

Thanks for the pep talk. I guess after wanting a fishing boat for 30 yrs but putting it off till almost 60 and getting a lemon right off had me kinda bummed.
So how do I spin the shaft?? What do I have to take loose to do so ??

Curious why greasing the shaft would not also grease the bearing if the seal is broken ?????

 

[merc850]

Could you post some pics. of the motor (180kb)? left - right - top; distributor at idle and full throttle and inside of cap. Don't attempt the distributor yet. Where do you live?

 

[Ghost1958]

Could you post some pics. of the motor (180kb)? left - right - top; distributor at idle and full throttle and inside of cap. Don't attempt the distributor yet. Where do you live?

I only have internet thru my phone so no resizeing photos but it seems to upload to other sites.

I can take the photos .
The inside of the distributer cap is clean now . I cleaned it out after last trip.
I'll have to get it on the water and run it a bit to dirty up the cap so you could see it.

Its too dark here now but I'll take the side pics etc tomorrow and try upload them.

If it throttles up like it should again until that oil or whatever gets in the cap again I'd say that's my problem.

Would greasing the shaft with marine grease not also put grease to that bearing if the seal side if it is kaput???

I live in NE Ky. About 30 mi from the Ky W.Vs line.

 

[Ghost1958]

Well was going to take pics when I got back from the lake so merc850 could see what was inside the distributer cap.

But at the lake it wouldn't even hit.
Its getting fuel, butterfliess are wide open, distributer travels from stop to stop.
I didnt get to check the spark as it got too late and honestly I need to step away from this motor before I hit with a sledge hammer.
I don't think it's getting a fire now .
First it's gas, then spark then it runs like it should for five min.

Then only idle then not all.

Im a fairly decent mechanic on motorcycles and cars.
I have to finish my sons motorcycle carb job then I can start fresh on this beast of a boat motor.

I've got muffs . I just have to get more hose so I can work on the thing without hauling it to a lake constantly


I'll get the pics up but since it never even sputtered the cap is still clean.

 

[Chris1956]

If you have no spark, I suggest you run the ign test as defined on the CDI Electronics web page. It will test all the ign components but the trigger.

 

[Ghost1958]

If you have no spark, I suggest you run the ign test as defined on the CDI Electronics web page. It will test all the ign components but the trigger.

Can't seem too find the webpage you mentioned.

 

[Mercurylips]

Link didn't work. Go to google and do CDI Electronics .com Scroll down to the troubleshooting page and choose Mercury.

 

[Ghost1958]

Link didn't work. Go to google and do CDI Electronics .com Scroll down to the troubleshooting page and choose Mercury.

Thanks much