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1997 Mercury 115 ELPTO 2+2 wont rev over ~2500RPM

jaclark91

Member
I bought a 97 Triton tr17 with a 1997 Mercury 115 ELPTO (serial number: 0G52****) motor on it about a month ago and I'm having an issue where it doesn't want to rev up over 2500 RPMs. It doesn't shake or anything once it reaches 2500rpm and it idles good so I think it's just running on the top 2 idle cylinders and never switches over to run on all 4. So far I have checked compression, all fuel lines and fuel pickup, spark on all 4 cylinders, rebuilt fuel pump, replaced inline fuel filter, checked that all butterfly valves on carbs were fully opening and closing, & checked that gas was getting to all carburetors.

I noticed on it earlier that there was one purple wire and two blue wires one coming from a module at the bottom right side of the motor that were unplugged. Looking at a service manual to a similar model motor (the 1997 jet drive one, mine has a prop) I think it may be to the rev limiter or the oil safety system. I also noticed that when I turn the key on there is no beep from the safety system like the manual says should happen. Could my problem be that it is going into limp mode or something because of the oil safety system or rev limiter not being hooked up right? I couldn't find anything about such a mode in the manual. Also does anyone know where I can get the factory manual for this motor for a reasonable price? I haven't had any luck searching Google as they all seem to be for the jet drive model.

Any insight would be appreciated. Thanks
 
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Is the accelerator pump working? The only oil warning on that motor is a low oil sensor nothing else. That motor should not have a rev limiter that was pretty much a jet only thing.
 
Is the accelerator pump working? The only oil warning on that motor is a low oil sensor nothing else. That motor should not have a rev limiter that was pretty much a jet only thing.

Hi thanks for the help. Should my motor have 2 of these modules stacked on top of each other at the bottom then if there isn't supposed to be an RPM limiter? The Jet drive service manual I'm looking at has the 2 stacked and calls one of them the RPM limiter and the other the Warning Module. Looking at pics on google of the rpm limiter and warning module the inner one on mine looks like the rpm limiter and the outer one looks like the warning module. The outer one on mine is completely unplugged. I tried to post some pics but can't get them to upload.

I have not tested the accelerator pump, I will figure out how to test it tomorrow. This is my first boat so I'm learning as I go. Thanks.
 
Need the whole serial #. What is compression? Do you have a motor that was converted from a jet. If you know for sure it's an overevv module just disconnect it.
 
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Need the whole serial #. What is compression? Do you have a motor that was converted from a jet. If you know for sure it's an overevv module just disconnect it.

Whole serial number is 0G528047. Compression was between 120-130 on all cylinders. As far as I know it wasn't converted from a jet. I'll disconnect it and see if it makes any difference next time I go to the lake.
 
Your motor comes up as a jet. More than likely it has been converted to a prop at one time.

Huh. I wonder if the rev limiter is causing the problem then. It is hooked up but it also may not even be hooked up right, since the warning module is completely unplugged from anything. Looking at pictures online I think the purple wire from the warning module is supposed to plug into the purple wire on the rev limiter.
 
Just to update this post I am still trying to figure out this issue. I plugged/unplugged the rev limiter and tested it and it didn't seem to make any difference. I also noticed that when you turn the key on the tachometer on the boat goes crazy. It also goes crazy once you start the motor and leave it in neutral. Once you put it in gear it hovers around 1000rpm and seems to work right mostly, it does pop up to a high rpm every now and then though and it doesn't sound like the motor is reving up when that happens. I tried lowering the idle using the idle adjustment screw on the side of the motor but the tach won't go under 1000rpm even if you screw it out until the motor dies. Last time I took it to the lake the tach pegged out at 3500 rpm and the engine started shaking/acting like it was missing.

I took all the carbs off as well and cleaned them/replaced all the gaskets. I noticed that 3 of them had torn 'boss gaskets' inside the bowl. I don't know if that could be my issue. I haven't had a chance to test it yet since I replaced the torn gaskets. I got a large industrial size plastic storage tank and cut the top out of it so I could lower my outboard into it to set the idle and low speed carb mixture screws with it idling in gear since my local lake only has one dock/boat launch and it is usually kinda crowded. I purchased a hand held tachometer to use to set the idle and stuff since I don't trust the one on the boat, still waiting on that to come in. I will check the accelerator pump as well when I get the carbs and idle adjusted correctly. I guess if it still doesn't work after that I will get a dva tester and start checking out the stator.
 
..."I will get a dva tester and start checking out the stator. "|

My favorite tool! Just cranking over it will tell you what's going on.

Jeff
 
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