[Kar_Man]

I'm new to boating, but somewhat experienced with cars. A couple years ago I bought a 17' boat with a 115 merc with only 630 hours on it. I bought it in mid-fall and I let it sit over the winter without doing much to it, then ran it a bunch last summer. I was probably out in it twice a week for wakeboarding and it was great. I had a 15 pitch prop to keep the revs up during wakeboarding ~23 mph and the performance was crisp, it shot out of the hole with 3 people in the boat and a boarder on the back and with 2 guys in it, would do 45mph. It has single barrel carbs with the distributorless thunderbolt ignition (2 switchboxes).

It has always had trouble idling, I usually start it in neutral with throttle, pull it back quickly to engage the forward gear and then quickly forward to get it some throttle before it dies. This season that problem is still there. Also, when a boarder falls and I back off to 1/2 throttle, the engine usually wants to die. It usually catches itself if I back off the throttle all the way (fuel delivery/float level issue?)

At the end of last year I attempted winterizing it but spraying storage seal into it as it shut down and then put some into the combustion chambers by pulling the plugs, I also did the leg oil. This year, it has been running with less power. It used to do 45 mph with the torquer prop, but now it can only get to 40 at best and it takes much longer to plane unless it's trimmed just right.

Things I am contemplating:
- de-carb? Would a carboned engine have reduced performance? I think that's an obvious answer... but just to confirm
- timing sync. I have never done this, but I didn't think it would work itself out of sync over the winter.
- Should the impeller be replaced? The tattle-tale shoots out... not super forcefully at idle, but it's also not a trickle - it's definitely a continuous stream.
- I did a compression test and 1-5 were all within 5 lbs, I couldn't get the gauge into #6... BUT I did an idle test where I pulled each plug wire one-by-one and the engine lowered it's speed everytime, so #6 is firing.. just not sure of the compression though.
- When I had them out, the plugs looked ok, but they're center fire ones and I'm not totally sure what I was looking for. They were wet, if that means anything, but not discolored like they were carboned up.
- I'm considering pulling the fuel pump to look at it, as I've read that pin hole leaks can cause wet fouling and stalling at idle speeds (which is what I have) and then stalling at 1/2 throttle after running at full throttle issue makes me think that maybe the pump isn't delivering enough gas.
- just recently I did the primer bulb/visible fuel line from transom to the motor and put hose clamps on all of the fuel lines on the tank side of the pump under the engine cover. Previously the lines were held on with zap straps... but that didn't help at all, no effect there.

It pulls smooth, it's just low on power compared to last year and I'm scared I've wrecked something... but I don't know what would cause this. I could start throwing fuel pumps, carb rebuilds

Thanks in advance! I have already got a ton of information from these forums, I appreciate everyone's input.

[Plainsman]

Welcome to iboats!!!

To see if it's the fuel pump, try priming the bulb and see if that helps.

Plugs should be a bit wet and tanned looking.

[OldMercsRule]

My son also has an 1981 inline 115 that I'm now gettin' all the bugs out of! (Too bad we don't have the 1982 115s that were the same as the 1981 140s)!!

It would be nice to know the compression of #6 to know fer sure. One bad hole could cause the loss of power problem yer havin'. They make testers that will fit the hole with a flexable line to the gauge, (I have one).

I don't think it is a good idea to pull the plugwires when running on those girls, (not positive about my potentially irrational fear of the Merc electronics), n' I only have one functional brain cell. Try an automotive spark tester instead. Ya never know when ya strain the electronics enough ta cause another failure especially on those six coil motors. (Most of my inlines are earlier ones with distributors, which I prefer.)

The decarb could solve yer problem. My son's motor starts, idles n' runs fairly good, but does not have the same snap outa the hole me other inlines do. Hope I don't have ta rebuild the carbs.

Try a decarb where ya spray it in the carbs n' let it sit fer a few days n' then fire it up n' run it fairly hard fer 30 minutes or so. N' maybe some Seafoam with some fresh mid grade, (89 octane), n' without alcohol if possible.

Good luck! JR

[Kar_Man]

thanks guys... I took a look at it today and when I tried the link & sync procedure, I noticed that the primary pickup wasn't bottoming out and that the advance linkage wasn't really connected to the throttle. It's connect with a sprint right at the top of the shaft/assembly and the spring had fallen off, so I don't think the advance was working, which would definitely explain some of the lost power.

The plugs were carboned up a bit too, so I cleaned them off. I will put new ones in and do a de-carb later on.

Thanks everyone.

[tashasdaddy]

do the decarb with the old plugs, it is hard on plugs, and recommended to replace them after a decarb.

[Kar_Man]

ok, thanks for the heads up.

how often should the impeller be replaced? the local shop says every year, but my book says every 50-60 hours of use.

like I said, the tattle tale isn't very strong, but I don't know when it was done last.