1987 80 hp 2k idle and soft misses???

[cobia186]

Its 8pm here in the cold Fl Panhandle. I just rebuilt the carbs on my 1989 merc 80 ENG# OB174624. It is running the same darn way???? On a cold start- starts right up and idles pretty smooth and slow. Then after 30-60 sec's it rev's to about 2k or a bit higher, and periodically misses. I have checked and rechecked the carb adjustments. I have looked for any leaks in the lines. What am i missing? The timing is dead on, I just don't uderstand. I physically heard this engine run last yr on my buddy's 17' skiff. She purred like a kitten all day. All he did was remove the oil injection because the oil tank cracked. Is there a vacume line that is already gone that might have hooked up to the oiler? I cant find a good diagram in my manual. Any input/opinions would be greatly appreciated. It would appear to act like a major air leak. Thanks again-

 

[cobia186]

Re: 1987 80 hp 2k idle and soft misses???

Oops!! I thought this was the Merc corner????? I must be on the wrong forum??

 

[cobia186]

Re: 1987 80 hp 2k idle and soft misses???

Ok- could a leaking/faulty fuel pump cause an engine to increase its rpm? That is the only thing left to replace- I do notice a drip every no and then from the fuel pump.

 

[Faztbullet]

Re: 1987 80 hp 2k idle and soft misses???

Thats a gravity feed oil system on that engine so it has no connections to engine block. From what you posted it could be several thing: (1)Double check your sync & link as it sounds like a carb throttle is cracked open. The misses are lean idle spits and if it does it enough times it could split the diaphram in fuel pump. (2) This could cause low fuel supply and make engine run lean(high rev) and spit, keep the primer bulb pumped tight and it it idles correctly the fuel pump diaphram is shot or the rubber checks valves have degraded and not closing.

 

[cobia186]

Re: 1987 80 hp 2k idle and soft misses???

Thanks for the input Faztbullet. I ordered a pump kit today. So when I get it Sat, I will rebuild it. As regards to the carbs, they are all closed, and the synk and link- it is spot on. FYI- this engine has been taken to 3 repair shops today. 1st said the removal of the oil tank has caused the issue. If I payed him $450.00, he would get me another tank and install it-(yeah-right). 2nd told me after a $95.00 fee that the synk & link is perfect, reeds appear good, and compression was good. He also told me the spark was good etc,etc. He couldn't tell me what the problem was, and he would need a 3hr min to find it. (Hwy robbery anyone??). the 3rd one told me my fuel pump was "more than likely" the problem. As he explained it- the fuel diaphram is ruptured allowing exccess fuel to enter the engine. Thus cause the engine to have a high idle??? SO Faztbullet, I am gonna run with the 3rd guy, after all, he was the only one caught the small leak from the fuel pump. I sure hope that is the problem. Thanks again-

 

[cobia186]

Re: 1987 80 hp 2k idle and soft misses???

OK- What the heck???? This engine is gonna be a reef addition this weekend!!! SO far- rebuilt carbs to spec, rebuilt fuel pump, synk and link has been checked and rechecked- I cant get this engine to idle below 1500-1600 rpms!! No vacum leaks anywhere. We have sprayed starting fluid around every crack-crevice-hose etc. no bogging or accelleration. Just the same 1500-1600. The engine has wonderful response. Put it in the water and the dam thing flies @ wot. While idling for 20 mins at 1500-1600 rpm the engine smokes alot. Not a lean condition by any means. The carbs are not flooding out due to float settings. This thing has been to 3 merc repair shops- no one can tell me why its doing this. I also adjusted down the timing while itr was running at 1500-1600 rpm- the idle does NOT change. I can turn the low timing darn near all the way out and it wont change the speed or the sound of the engine. I physically make sure that all the linkage is working/moving as it should. I watch the timing components move-no change. Compression test are within 4%. The engine passed all leak down test. I am at a loss as of now.

 

[cobia186]

Re: 1987 80 hp 2k idle and soft misses???

problem solved- found a burned wire on the trigger, wht/blk to be exact. replaced burned portion of the wire, and now the engine runs perfect.