1997 Merc 175 offshore

[1997mercury]

I have a 1997 Mercury 175 offshore. I changed the fuel lines and spark plugs as I just bought the boat. Has aluminum tank and lots of fuel ran in it, I do not think its an eth issue. Problem: After traveling through a no wake zone for a bit it requiers me to throttle up as it starts to spudder out but will idle in the driveway all day, also it is hard starting only after running for a while. I have to wide open throttle and choke it to start it. But in the driveway it fires right up. ??? It runs great at 1/4 plus throttle with no issue, just the starting and low speed travel I have issues. Also I am not sure if this is an issue but the fuel ball goes soft after running it for a while but is hard in the driveway. I checked the lines and have no visible line leak/air leaks. I was told it sounds like a carb adjustment issue, I have no idea. What say you?

 

[j_martin]

Re: 1997 Merc 175 offshore

It's a bone. Bring it over and I will dispose of it for you.

Actually, not knowing where you are or what the weather is, it's hard to tell much. That engine can be a little cold blooded, and in cold weather what you describe isn't too far off norm.

I consider fuel pump rebuild an annual maintenance item. Some don't, but I do.
If they are questionable, it is well worthwhile to go through the carbs. Needles and seats are usually good. Gaskets seem to wear out or get old. The main problem is usually a little dirt or debris in them. Gasket kits are pretty cheap, and the carbs are pretty simple to work on, just be neat, careful, and methodical.

At idle, the engine might do better if trimmed out a bit from minimum. The carbs when properly adjusted could tend to flood a bit when the engine is tucked under.

hope it helps
John

 

[1997mercury]

Re: 1997 Merc 175 offshore

Roger all, I appreciate the response. I am in Sunny SW Florida so not the cold. Probably just gonna go thru the carbs and pump. I did notice what appears to be a PCV type valve on the head with no line hooked to it and when I plug it with my finger it idles dwn and smooths out, but there is no line in sight that appears to have fallen off. I do not have experience with boat motors Thanks.

Adam

 

[Fl_Richard]

Re: 1997 Merc 175 offshore

Adam,
Try looking for it here. Good diagrams if nothing else!

http://www.boats.net/parts/search/Merc2/Mercury/parts.html

You should be able to find your parts and what there called as well as hose routing. On my Johnsons that part would be a pulse limiter that hooks to the VRO fuel pump.

Dales neighbor Richard

 

[Dukedog]

Re: 1997 Merc 175 offshore

Look on tha starboard side of tha carbs. They should have fittings and 1/4 tubing tying them together. Tha bottom carb should have a "t" with a tube going up to tha middle carb and probably nothing on tha bottom of the "t". There should have been a 1/4" tube going from tha bottom of this "t" to either barb on tha thing you found on tha starboard head. One barb stays open. That is an air sensor that as a bearing on tha air/fuel mixture.......

Don't confuse this with tha fuel lines that are on tha same side.

 

[1997mercury]

Re: 1997 Merc 175 offshore

Thanks Dales Neighbor! and Dukedog your right, one is going to a carb and the other must/is a breather, I was wondering bout that as I did not find any lines laying loose as I mentioned. Thanks will figure this out soon.

Adam

 

[Dukedog]

Re: 1997 Merc 175 offshore

Don't think any of tha diagrams will show tha fittings in tha carburators that I'm talkin' about. Don't know why. They only show tha fuel line fittings. They will show tha air sensor in tha head though. Sometimes tha tube gets remover/disreguarded for what ever reason.............

 

[1997mercury]

Re: 1997 Merc 175 offshore

Dukedog....I been a car guy my whole life, and know the motor needs to breathe somewhere, but with that said plugging the breather off on a car motor would not change the behaving of an engine. This is my concern with this port, when I block it off with my finger it seems to smooth out and respond properly. Can't seem to find any decent diagrams...maybe I will head to West Marine and pick up a Chiltons manual. Does anyone know where there is decent digrams of this 1997 175 Merc???

Out Here

 

[Dukedog]

Re: 1997 Merc 175 offshore

Tha only place you will find it is in a MERCURY service manual that covers your motor. You will have to get it from Mercury (dealer) Its not available on line. It will not show up in any parts break down other than that of a "thermal air valve".

Its kinda like tha old thermal operated automatic choke of tha good 'ole days but instead of operating butterflies it varies tha air/fuel mixture in tha idle circuit. With it hooked up to tha carburators it should make a difference if tha carbs are in good shape. But with it not hooked up you are right about it shouldn't change anything by puttin' your finger over either/or both ports.

 

[Dukedog]

Re: 1997 Merc 175 offshore

I block it off with my finger it seems to smooth out and respond properly.


Tha port on tha sensor or tha port on tha carb?

 

[j_martin]

Re: 1997 Merc 175 offshore

Mercury lists the book as a part number in their parts lists. Once you have that number, you can sometimes score a used one on eBay or Amazon.

 

[1997mercury]

Re: 1997 Merc 175 offshore

All,

I think we figured it out with the help you guys and of a new neighbor who happened to be a Marine mechanic for 12 years. God send in the least, I did pick up a Mercury Manual for 30 bucks at West Marine...good investment to me for future issues. We pulled the air cleaner while running and we both immedately noticed a little too much fuel comming out the bottom/third carb. He seems to think it is nothing more than a stuck float or perhaps a little to much debris or just the right amount to cause the issue I am having. So tomorrow I am pulling it off, inspect it, hopefully just be able to clean/soak it in some engine cleaner and slap it back together and on and see what happens. Worst case I will rebuild it. I really appreciate all the responses and good intel. You guys know your stuff and am a first time Iboats forum guy. Great site. I will be in touch with the results tomorrow night.

Semper Fi

 

[1997mercury]

Re: Carb misting fuel Issues 1997 Merc 175 2 stroke

Re: Carb misting fuel Issues 1997 Merc 175 2 stroke

Well I pulled the bottom carb dismantled it completely and inspected it. I cleaned the jets and ports and valve body with Mercury Engine tuner/carb cleaner. Everything looked great, re-installed it and started it up and I still think there is more than usual fuel coming out of the port side bottom carb...more than any other, and when I throttle it up its the only port that sprays a mist of fuel out. What could this be from? It seems to be loading up or overfueling a bit and clears out with a quick throttle up and back. Any ideas?

Thanks

 

[j_martin]

Re: Carb misting fuel Issues 1997 Merc 175 2 stroke

Re: Carb misting fuel Issues 1997 Merc 175 2 stroke

Well I pulled the bottom carb dismantled it completely and inspected it. I cleaned the jets and ports and valve body with Mercury Engine tuner/carb cleaner. Everything looked great, re-installed it and started it up and I still think there is more than usual fuel coming out of the port side bottom carb...more than any other, and when I throttle it up its the only port that sprays a mist of fuel out. What could this be from? It seems to be loading up or overfueling a bit and clears out with a quick throttle up and back. Any ideas?

Thanks

Squeeze the primer bulb with a firm handshake (not white knuckle) and hold it. If fuel runs out of that carb, the needle, float, seat gasket, or casting is bad.

If it doesn't, and fuel spits out of that one at idle, look to the reeds.

hope it helps
John

 

[Faztbullet]

Re: 1997 Merc 175 offshore

Here is the thermal valve diagram..