1975 Mercury 7.5 progress report

[bob1340]

Re: Funny thing just happened..

Re: Funny thing just happened..

Yes. There is also a seal on the intake grate. So one end of the intake tube goes into that and another on the water pump. Then another on the Top of the water pump which holds the long part of the water tube which sends water up to the motor. Those seals. Whats the purpose of the rubber "oil seal" that just sits on the top of the water pump around the drive shaft? THere isn't even any oil in that part of the lower unit...

Okay.

I think the idea behind the top seal is to prevent any hot water from the motor entering the pump.

 

[Wingedwheel]

Re: 1975 Mercury 7.5 progress report

I believe your asking about the "slinger" seal. Its just to keep any muck from running down the shaft and accumulating at the base.

 

[MassillonBuckeye]

Re: 1975 Mercury 7.5 progress report

I believe your asking about the "slinger" seal. Its just to keep any muck from running down the shaft and accumulating at the base.

Ok good info on that one, but more wondering about the water tube guide seals. Should you be able to pull the tubes out of the seals? I couldn't. I had to pull the whole seal, still attached to the tubes, out of their respective housings. Then cram back into housings still attached to the tubes. Seemed like those seals were glued onto the water tubes.

 

[MassillonBuckeye]

Re: 1975 Mercury 7.5 progress report

Inspected and cleaned the carb with compressed air. New fuel strainer gasket and cleaned the plugs and she ran like a champ tonight. No symptoms from before. New issue I addressed in another thread, but had some water/milky oil atop the water pump when I checked it earlier. I relubed LU and reseated/tightened water pump housing before going out tonight. Will check LU again tomorrow evening for more oil. Going to use some silicone on the exhaust divider as J_Marting recommended.

 

[MassillonBuckeye]

Re: 1975 Mercury 7.5 progress report

Well 1 year later and its still a dog at WOT. Surges a little bit while rolling with waves. Seems orientation of motor is affecting it slightly. Last year I could feather the choke a bit to get it to cooperate, but now, even the slightest amount of choke kills the motor. One guy says Coils, another says Carbs/jets. Any advice? One other thing, as the day went on(starting and stopping motor), it got harder to start. It wouldn't start in Neutral in the "start" throttle setting. I'd have to put it in gear to open the throttle more to get it to start. Thanks for the input guys

 

[MassillonBuckeye]

Re: 1975 Mercury 7.5 progress report

Was also advised to clean the one inaccessible jet by drilling into the cap to remove. Is this ever necessary? Was going to do needles/jets/float tonight when I get home from the Ohio State Fair. Weee!! New tank/line as of last year. I don't think this engine was run enough on ethanol for it to have rotted and varnished the lines. This thing looks like new actually. Any advice?

 

[MassillonBuckeye]

Re: 1975 Mercury 7.5 progress report

The Venturi was broken. Was missing one of the tabs on the side. Replaced and now runs great! Now to just get the new float adjusted.. Its taking a lot more pulls to start and smells of gas. I'm assuming its flooding? I tried to make the bowl level with the carb body when hanging upside down.

 

[bgc]

Re: 1975 Mercury 7.5 progress report

The Venturi was broken. Was missing one of the tabs on the side. Replaced and now runs great! Now to just get the new float adjusted.. Its taking a lot more pulls to start and smells of gas. I'm assuming its flooding? I tried to make the bowl level with the carb body when hanging upside down.

Can you post a photo of the broken venturi?

 

[MassillonBuckeye]

Re: 1975 Mercury 7.5 progress report

Can you post a photo of the broken venturi?

Will do when I get home. Can anyone advise on setting the float properly? I'm having trouble finding exact measurements and how-to. Im assuming its not adjusted properly because its now hard to start and smells of fuel after a few pulls. When upside down, the bottom of the float looks parallel with the carb body. Any other adjustments to make?

 

[MassillonBuckeye]

Re: 1975 Mercury 7.5 progress report

A serious nap session overtook me yesterday after work so I did not post a pic of the venturi, but its basically a short round tubular piece of plastic with two wings that hold it centered in the carb. If one of those wings break, the thing can basically spin sideways Greatly restricting flow through the carb. So essentially, instead of a nice "donut hole" for stuff to flow through, you have a "wall" which it has to then flow around.

Part#19 in the diagram below. 2 "wings". One wing breaks and it can then spin freely and wreak havoc on your fuel flow.

View attachment 108512

http://www.boats.net/images/diagrams/Merc2/MERMAR/13716/7.png

Someone mind helping with the float adjustment?

 

[merc850]

Re: 1975 Mercury 7.5 progress report

Here's a page from the 1975 Manual

soon the whole manual will be on this site!

 

[MassillonBuckeye]

Re: 1975 Mercury 7.5 progress report

Here's a page from the 1975 Manual
View attachment 108577
soon the whole manual will be on this site!

Ahh, thank you very much. Although this little card I have advises: .280/ .320 float setting WMA/WMB carb and.320/.360 float setting BA/BB Carb. .320 milimeters? Im so confused. I set the float even with the carb body which is what I've seen most people advise. But I've also come across some info on this carb where the float has to be high, which to some didn't look right.
I'm so confused. I'm about to just put the old float back in and see. But different floats require different settings soooo. Ack.

Is my carb WMA/WMB or BA/BB? Its tillotson.

I think I understand. What was confusing me was noone really referenced setting the float Drop as well. Just making it even with with body. Which I did but obviously wasn't enough.

1/4" (plus or minus) 1/64" from top of float to casting of carb(carb held upside down) by bending float tab(plastic), then 1/16th-1/32nd" between bottom of float and main jet. Metal tang is used to adjust this. Sound about right?