Power loss 115 merc.....STILL....update!

[Madpole]

ie: No power past 1/2 throttle.

OK guys. (Laddies, Charlieb Lone Dove, etc.) You recommended a link and sync, but I don't have a timing light (yet). Just got back from lake. Disconnected the idle stabilizer and tried...still no improvement.
However,!!!! I was able to get the engine to rev up to full speed by working the enrichment valve. I really had to work it! When it finally got revved up it ran like a scalded dog and stayed that way until I throttled back to 1/2 and then back to same problem.....only 1/2 speed. I throttled up and tickled the enrich valve until it took off again, and ran fine for as long as I would keep the throttle at full speed. It appears the timing is fine as long as I can get it revved up and on plane.
I think I am real close.....fuel pump rebuild kit? New fuel connector? Old one sucking air???

C'mon guys....we can do it!

(thanks to you all)

Madpole

 

[Chris1956]

Re: Power loss 115 merc.....STILL....update!

Actually it is possible it is mis-adjusted idle mixture on carbs. Richen them up a bit (1/8 turn at a time, and test in between) and see if it improves. Normally the motor will bog and maybe stall when given throttle. Do you have that symptom?

 

[CharlieB]

Re: Power loss 115 merc.....STILL....update!

What Chris said.

Idle mixture must be adjusted RICHER than 'Best Idle' IN gear and IN the water to provide the additional fuel to accelerate.

Adjust each idle mixture screw OUT just the width of the screwdriver bladeslot and retest acceleration.

ANY hesitation, bog, lean miss, or cough, is indicate that it still needs more idle mixture, adjust out another width of the blade slot and retest acceleration.

Repeat to perfection.

You are getting pretty close now, just one or two small tweaks and you'll be there.

 

[Laddies]

Re: Power loss 115 merc.....STILL....update!

If your lean out at mid range try taking the back draft jets ( bowl jets) out of the carbs if they are to small they can cause a lean out.

 

[Madpole]

Re: Power loss 115 merc.....STILL....update!

Thanks guys! It looks like we have come full circle. the idle mix was one of the first things I started with (as per suggestions on this board.) But a lot has been done since then, so I will try that again as soon as I can get back on the water.
To answer Chris1956's question...No the engine does not bog down when throttle is pushed past 1/2. Nothing happens. Now, for some reason I can get the revs up and the boat on plane when I press the enrich. valve numerous times until it catches. It is not automatic. I really have to work at it. But, when it catches it runs great.

Incidentally, Apparently the idle stabilizer wasn't doing anything. The engine idle is actually faster without it and disconnecting it may have improved the whole situation, getting me to where I can actually make the engine rev.

I will keep you all posted. Thanks again.
Madpole

 

[wired247]

Re: Power loss 115 merc.....STILL....update!

Sounds to me like your float adjustment might be off a bit. Those carbs have terrible off idle transition vacuum signal and wont flow gas well enough to get into high speed mode if the float level isnt exactly where it needs to be. Some carbs have a high vacuum signal and float level doesnt matter for squat but not the inlines. Bumping the enricher gets you over the hump as you have found out.

 

[Madpole]

Re: Power loss 115 merc.....STILL....update!

Those carbs were reworked by a (so called) professional. One other thing, the last time I primed before starting, the last squeeze of the bulb produced fuel to flow from the top carb. Is this normal? I thought the floats were supposed to prevent flow when the bowl gets full? Maybe a symptom?

 

[wired247]

Re: Power loss 115 merc.....STILL....update!

Fuel pressure on those motors is ridiculously low. 1-2 lbs ish. Pumping the bulb you can easily build more pressure than that and overwhelm the needle and flow gas out the carbs.

"Professional" rebuild or not. I'd take a serious look at the float level. Then I'd make sure my timing was set right.

 

[Chris1956]

Re: Power loss 115 merc.....STILL....update!

A lot of the "professional" mechanics have no/limited experience with inline six motors. They do have some querks.....

 

[Madpole]

Re: Power loss 115 merc.....STILL....update!

EUREKA! I found the problem, and I fixed it with a RUBBER BAND!!!! the throttle advance unit at the top of the linkage was getting stuck at about 1/2 throttle. It appears the torsion spring is too weak to push the advance rod and it gets stuck in about the middle of its travel. The whole assembly is loose from wear. I put two large rubber bands on the linkage as a temp. fix and tried it at the lake.
Motor now runs like a cheating housewives lover....after hubby pulled in the driveway!

Thanks to all of you for the responses and suggestions. I completed the link and synch and carburetor float calibrations, before discovering the real problem. But all is now set to factory specs and it runs great.

Now my problem is finding replacement parts. most of this assembly is "obsolete" and cannot be found on the usual websites. Does anyone have a suggestion of where I can locate new or used parts for this assembly.? The rubber bands will only last a short time!

 

[mr 88]

Re: Power loss 115 merc.....STILL....update!

A bungy cord will out last the rubber band,just kidding. You can try ebay or search on here. I have seen many topics that have links to various used/nos suppliers.Parts are available,if no one chimes in send me a pm and I can give you a number of a guy in NY that will have said part.