1983 115 Inline 6 running rough and slow

[RockotheNut]

Just purchased an old '92 Skeeter fish and ski with a '83 115hp Inline 6. Serial 6268368.<br /><br />Took the boat out and didn't really have a difficult time starting. Just did the usual, prime, choke, bit of throttle, etc. Seems to idle well. Run at high speed and rpm's wouldn't go over 4200-4500. Still seems pretty fast. After it was warmed up, it wouldn't start. Test pointed to the starter, so I tore it down and found a rebuilt piece of junk. Replaced starter. Starter issue fixed. Also when warm, it wouldn't idle well and died going into gear.<br /><br />Checked compression of first 5 cylinders. Any tips on how to access the 6th? First 5 cylinders all 130. 6th is probably ok as well.<br /><br />Pump primer bulb and fuel leaks from the 3rd Carb through a small opening (float overflow? ) as well as directly from carb intake. Start engine and let idle. Fuel still leaks from the 3rd carb.<br /><br />Pull spark plugs and engine tempo changes only on the first 4 plugs. 5 and 6 don't change.<br /><br />As a sanity check, does this just point to a carb rebuild? I figure I'd rebuild all three carbs and perhaps the fuel pump.

 

[phatmanmike]

Re: 1983 115 Inline 6 running rough and slow

yes, clean the carbs and rebuild the fuel pump. easy and cheap. these motors( inline mercs) need lots of fuel to get started, like its pouring out of the carbs. <br /><br />nature of the beasts.<br /><br />check your carbs that they open at WOT all the way, and check that the prop isnt too big. <br /><br />you absoluetly do NOT want to lug an inline. you should spin that thing up closer to 6K. mine spins 5700 at WOT

 

[Chris1956]

Re: 1983 115 Inline 6 running rough and slow

Rock, I was able to put a 90 degree elbow on my compression gauge, between the gauge itself and the rubber fitting. This allows me to check cylinder #6's compression. <br /><br />You need to fix/adjust the leaking carb. The way it is now, you may be fouling out one or two cylinders, causing your power problem. I would star with inspecting the float and inlet needle and seat. Sometimes those floats crack or deterioate (depending on whether they are hard plastic or foam). Replace float and inlet needle and seat, clean the plugs and see if things improve.

 

[Clams Canino]

Re: 1983 115 Inline 6 running rough and slow

Yes... clean the carbs and then search this board for my "timing and sync" post - and you outta be all set.<br /><br />-W

 

[RockotheNut]

Re: 1983 115 Inline 6 running rough and slow

Thanks all, I have gotten this far by all the great posts on this board.<br /><br />I did remove the carbs last night, and they and the head inlets are very clean. I'll get inside the 3rd carb to investigate further. Bad float would be my guess. We'll see.<br /><br />The 90* elbow idea sounds great. I'll have to work that up. <br /><br />I've seen the timing and sync post. I'll definitely follow that when I put her back together.

 

[RockotheNut]

Re: 1983 115 Inline 6 running rough and slow

Carb cleaned and rebuilt. Convinced carb is fine. Fuel runs out of throat when running. Although engine sounds good, it is only running on 1st 4 cylinders.<br /><br />Compression on cylinder 5 is good as is spark, but engine doesn't change when plug wire is pulled on 5. Haven't been able to get into 6 to check it. T<br /><br />Since compression is good and fuel is getting to the carb, my guess is fuel is not being "sucked" into the cylinder. Even if 6 was bad, would 5 still operate? What about the intake valves?<br /><br />If I can't fix myself, I can't see getting it pro repaired. This engine can't be worth more than several hundred. If I repower, perhaps a used engine a few years old? Does that make sense?

 

[Clams Canino]

Re: 1983 115 Inline 6 running rough and slow

You maybe need to replace the float needle and seat on the bottom carb and possibly the float. It's not running on the bottom two perhaps because it's flooding them out. Fuel should not run out of the bottom carb any more than it does the top two.<br /><br />When running at say 2000 RPM - can you feel a vacuum on the bottom carb? Does the idle needle on the bottom carb have an effect on it?<br /><br />Forget book value... you can't replace it with new stuff and get anything better than you've got. You'll be happier fixing it. If the compression is good all the way around (and yours is) than it's prolly an easy fix once you find it.<br /><br />-W

 

[tashasdaddy]

Re: 1983 115 Inline 6 running rough and slow

it's not worth fixing. send it to me and i'll dispose of it for you.

 

[jnewtonsem]

Re: 1983 115 Inline 6 running rough and slow

Rock go over to screamandfly.com lots of guys over there who've worked on inlines for years. They can give you some more good adive on where to look. good luck

 

[RockotheNut]

Re: 1983 115 Inline 6 running rough and slow

I did change the seat, needle and float during the rebuild. I'll check for suction as you suggested, Clams. Another thought hit me. I guess I could always just swap the 2nd and 3rd carbs to see if the problem moves. If it moves, I would still have a carb problem.

 

[RockotheNut]

Re: 1983 115 Inline 6 running rough and slow

Wrap up. It's fixed.<br /><br />Thanks Clams. Basically, during the rebuild, some gasketcinch must have broke loose somewhere and was causing the new needle to bind. DOH!!!<br /><br />I did go ahead and swap the 2nd and 3rd carbs, just in case, but after putting it back together, it fired right up with no fuel leakage and 5 & 6 were firing as well. Real nice.<br /><br />Lesson learned, be real clean and careful rebuilding the carbs.<br /><br />Thanks again.

 

[tashasdaddy]

Re: 1983 115 Inline 6 running rough and slow

darn i told you, it wasn't worth fixin'.

 

[Clams Canino]

Re: 1983 115 Inline 6 running rough and slow

Hey J (Issac) Newton.... there's a lot of guys HERE that have been working on inlines for years. When you get advice on S&F for inlines you need to be able to determine if it's race specific advice for a 6500 rpm screamer - or just good sence for a fishing motor. No need to filter the input here.<br /><br />-W

 

[jnewtonsem]

Re: 1983 115 Inline 6 running rough and slow

Sorry Clams, not trying to ruffle any feathers. It's becoming apparent that there are some guys on this board that are also familiar with inlines. Not been here very long-and you are right the guys on S&F are high performance guys. Although their conclusion with the inlines is that there is not much you can do to an inline to improve performance. Just maintain it. Once again- didn't mean to offend any one.

 

[jnewtonsem]

Re: 1983 115 Inline 6 running rough and slow

Also dealing with a motor that hasn't been made in 20 years and finding mechanics familiar with them is getting scarce.

 

[Clams Canino]

Re: 1983 115 Inline 6 running rough and slow

They are right too.... At it's best config (Merc 1500) the motors are about as tricked out as they can possibly get - and already a little unstable. 1.5 hp per cubic inch is asking a lot.<br /><br />-W