Multiple questions for first time boat owner regarding tune up of an 87 115hp ELTPO

[BrianSmithFishn]

MERCURY

1987

115 ELPTO

Model Number 1115727

Serial number B182713

I bought this old bass boat off a buddy for $1200 and this is the motor that is on it. It runs, but not as good as I would like it to do to his lack of maintenance. He owned it for about 4 years in college and never did anything to it besides change gear oil and spark plugs. I cleaned out the gas tank, bought gasket kits for the carbs along with new floats and valve seats. New fuel filter, and water pump kit. Is there anything else I am missing to get this running reliably? I am a first time boat owner, I do not know much about mechanical stuff but I know enough to watch videos read up on forums and turn a wrench to figure it out. Any info or help you could give me to get me out on the water will be greatly appreciated! Thanks for your time and responses in advance!

1 - What gear oil to use.

2 - What spark plug model # do I need.

3 - Any suggestions or help on cleaning/ rebuilding the carbs, leave them on or take them off? Also suggested screw settings after rebuild and clean.

4 - Previous owner mixed oil into the gas tank at I believe 50-1 is that correct and also suggested brand oil to use.

5 - Im curious about the gear box and bearing carrier / prop shaft oil seals. The health of them all. There are 2 grease fittings on the bearing carrier, Just curious proper maintenance of that whole unit. Also what ever grease fittings on the motor and the proper grease to use on them.

I compression tested the motor several times. Im getting in psi:
Cyl 1 - 80
Cyl 2 - 70
Cyl 3 - 80
Cyl 4 - 80
Cyl 5 - 80
Cyl 6 - 80

6 - Is this ok? Are they good readings, i.e. healthy and ok to run. What should they be reading at and when should I be concerned?

7 - The engine is missing the front cover with the knob and the sound seal/ blanket. I have the wrap around cover and the top piece. Is it ok to run like this or does that whole front system act as an air box to the carburetors? I ask because as it looks to me they do not run air filters or a box and I was concerned about water or debris getting in the carbs.

 

[ondarvr]

Isn't a 1987 115 ELPTO a 4 cylinder.


Just checked, it's a 6 cylinder.

 

[jimmbo]

TE=BrianSmithFishn;n10231948]

MERCURY

1987

115 ELPTO

Model Number 1115727

Serial number B182713

I bought this old bass boat off a buddy for $1200 and this is the motor that is on it. It runs, but not as good as I would like it to do to his lack of maintenance. He owned it for about 4 years in college and never did anything to it besides change gear oil and spark plugs. I cleaned out the gas tank, bought gasket kits for the carbs along with new floats and valve seats. New fuel filter, and water pump kit. Is there anything else I am missing to get this running reliably? I am a first time boat owner, I do not know much about mechanical stuff but I know enough to watch videos read up on forums and turn a wrench to figure it out. Any info or help you could give me to get me out on the water will be greatly appreciated! Thanks for your time and responses in advance!

1 - What gear oil to use.

A marine grade SAE 90 gear oil

2 - What spark plug model # do I need.

NGK BUHW

3 - Any suggestions or help on cleaning/ rebuilding the carbs, leave them on or take them off? Also suggested screw settings after rebuild and clean.

Best cleaning is done off. Idle mixture screw - 1 1/2 turns counter clockwise from barely seated. Final adjustment to be done running and under load

4 - Previous owner mixed oil into the gas tank at I believe 50-1 is that correct and also suggested brand oil to use.

50:1 is correct. Can't go wrong using Mercury 2 stoke oil. Others will insist any TCW-3 oil is fine

5 - Im curious about the gear box and bearing carrier / prop shaft oil seals. The health of them all. There are 2 grease fittings on the bearing carrier, Just curious proper maintenance of that whole unit. Also what ever grease fittings on the motor and the proper grease to use on them.

When their health is bad they leak. The grease nipples are there to keep the bearing carrier greased so it will slide out easier when removal is needed

I compression tested the motor several times. Im getting in psi:
Cyl 1 - 80
Cyl 2 - 70
Cyl 3 - 80
Cyl 4 - 80
Cyl 5 - 80
Cyl 6 - 80

6 - Is this ok? Are they good readings, i.e. healthy and ok to run. What should they be reading at and when should I be concerned?

All are evenly low except #2 and it looks like it is within 15% of the rest. I suspect an inaccurate compression tester

7 - The engine does not have the front cover with the knob or and any sound seal/ blanket. Just the wrap around cover and the top piece. Is it ok to run like this or does that whole front system act as an air box to the carburetors as it looks to me they do not run air filters or box.

It looks ugly, but it doesn't hurt to run like that. It will be a little louder. The sound liner was discontinued when the switchbgoxes were moved to the starboard side of the engine. Trapping heat was the reason. That engine does not use silencers on the carbs. Air filters generally aren't used on Marine engines

[/QUOTE]

 

[BrianSmithFishn]

Cyl 1 - 80
Cyl 2 - 70
Cyl 3 - 80
Cyl 4 - 80
Cyl 5 - 80
Cyl 6 - 80

6 - Is this ok? Are they good readings, i.e. healthy and ok to run. What should they be reading at and when should I be concerned?

All are evenly low except #2 and it looks like it is within 15% of the rest. I suspect an inaccurate compression tester




Ok, thank you so much for the help! Someone else has told me they think the compression tester is janky too. I just purchased the tester from harbor freight this is the first thing out of the package it was used on, I will try and see if I can borrow a buddies to compare. Also you say they are low, do you know what they should be around and or when I should be concerned? This is about my only concern at this point. is the health of the motor. I really don't want to have to tear it apart. At least not this year.

 

[jimmbo]

See what the second compression gauge reveals.

 

[DavidMoore]

I think with compression that low would give starting and running issues, so I don't believe the readings.
You should be concerned when the readings are uneven, rule of thumb is they should be within 15% of each other. The good news is yours are even and the low values are most likely to do with the gauge / test procedure.

Are the readings being done with all fully charged battery, plugs removed and grounded, and the throttle plates wide open?

 

[BrianSmithFishn]

I think with compression that low would give starting and running issues, so I don't believe the readings.
You should be concerned when the readings are uneven, rule of thumb is they should be within 15% of each other. The good news is yours are even and the low values are most likely to do with the gauge / test procedure.

Are the readings being done with all fully charged battery, plugs removed and grounded, and the throttle plates wide open?

Yes how ever I do not have the engine hooked up to the gas tank and it has been sitting for a long time, would that contribute to low numbers?

 

[DavidMoore]

I don't think so.
variables will be the accuracy of the gauge (can be very inaccurate which is why you concentrate on the spread of the reading rather than the value indicated)
The amount of air the engine can breathe (throttle plates open)
Rotational speed (fully charged battery, all plugs removed)

I would wager you don't have much of a problem and doing the readings again with a different gauge will give you more confidence in this.
Don't get too hooked up on numbers, it's consistency you want. The lowest value should be with 15% of the highest value.

 

[racerone]

Throttle plates do NOT need to be open when doing compression test on this motor !