175 Mercury Black Max cuts out on acceleration

[Crest990]

I'm brand new to the forum, and am in need of help from all of you "experts". I have a 1977 175 Black Max on a Crestliner 990. The engine starts and runs great. With muffs, the engine will rev and seems to be working great. The problem I'm having is this:<br /> After sarting and running about 1200 RPM, when I advance the throttle past about 1/4 the engine kills completly, and then I have to restart. I've already tried the small gas tank at the back and ckecked fuel pump, changed plugs, etc. If I "baby" the engine with the choke until it almost dies, then punch it to WOT, the engine bogs a little, and then takes off up to about 42 MPH. Any help is appreciated. (overpropped?, jets too small?)<br /><br />Thanks for your help.

 

[Laddies]

Re: 175 Mercury Black Max cuts out on acceleration

Sounds like dirty carbs, the reason it revs on muffs is there is no load on the engine

 

[andy6374]

Re: 175 Mercury Black Max cuts out on acceleration

Agree with Laddies, time for a carb cleaning. <br /><br />-andy

 

[LubeDude]

Re: 175 Mercury Black Max cuts out on acceleration

Well, I will be watching this one, my 150 has done this from the time I bought it and I have done everything imaginable to no avail. Sure seems to be a lean problem as I can get past it like you say by using the inrichment button. Dies when I come off plane also unless I push the key in just before stopping.

 

[andy6374]

Re: 175 Mercury Black Max cuts out on acceleration

LubeDude-<br />Silly question perhaps..<br />Have you completely rebuilt the carbs, not just cleaned them.<br /><br />If you have a nice friend who has the same motor, try taking off his carbs and using them on your merc to see what happens.<br /><br />-andy

 

[Crest990]

Re: 175 Mercury Black Max cuts out on acceleration

I have not completely rebuilt the carbs recently, however, they were completely rebuilt a few years ago by a pro shop before it was parked. The previous owner described the same problem. This is what he had done. Gas tank removed, inspected, and cleaned. Carbs rebuilt. Fuel pump rebuilt. I have cleaned the carbs, but maybe need to try another rebuild... What about the high speed jets or something? Could that be a problem? Could anyone help me with the proper jetting charts (about 5000 ft).

 

[LubeDude]

Re: 175 Mercury Black Max cuts out on acceleration

Originally posted by andy6374:<br /> LubeDude-<br />Silly question perhaps..<br />Have you completely rebuilt the carbs, not just cleaned them.<br /><br /><br />-andy

The only thing there is that I can see between the two would be needles and seats, and they were replaced also. New gasket kits were used both times. Ive tried two different float settings also. The only thing I did that helped just a bit was rejetting the Idle curcuits. Am I missing something as to "A total rebuild",that I dont know about?

 

[Laddies]

Re: 175 Mercury Black Max cuts out on acceleration

 

[Calabrio]

Re: 175 Mercury Black Max cuts out on acceleration

How complicated is it to rebuild the the three carbs?

 

[andy6374]

Re: 175 Mercury Black Max cuts out on acceleration

Not very. Usually a rebuild involves new gaskets, needles and seats. Sometimes new floats and even less frequently new jets.

 

[LubeDude]

Re: 175 Mercury Black Max cuts out on acceleration

It will take you a whole day if you havnt done it before and are a pretty decent mechanic. Get a manual and take a lot of notes on the wireing you will have to disconnect. The average mechanically inclined person can do it.

 

[Crest990]

Re: 175 Mercury Black Max cuts out on acceleration

All,<br /> Thanks for all the advice and help with this one. I've got the boat to where it's OK now. All it took was some different jets and another rebuilt fuel pump including checkvalves, a new bulb, a new fuel line, and a new tank pickup tube. I don't really know what it was that finally solved the problem, but it works now. It will ocassionally cut out, but that doesn't happen like it used to. <br /> Happy boating this summer!