1981 Merc 115 i6 issues

[Tripp Halbert]

Hello all! It has been years since I have been on here but man I love this website and community! Today I need help!

I bought a 1982 18’ Glastron Carlson with a tower of power 1981 Mercury 115hp inline 6 mounted on the back.

At first glance this engine looks to shiny to be 40 years old and I was very excited to learn it was in full mechanical working order (after some hours of coarse).

So to date the issues I have addressed.

-3/6 cylinders fired (replaced firing boxes and now all 6 work)
-Tested compression (120psi on all six)
- Rebuilt all 3 carbs
-rebuilt impeller
-cleaned out fuel pump (gasket slightly torn and filter heavily clogged, awaiting parts to rebuild)
-idle stabilizer red wire was completely rusted to the unit itself (cannot find replacement, bypassed/wired without and to my knowledge the timing needs to be adjusted??)

So the engine I have had running good on the ears (idle 950 rpm’s, will idle 30 minutes if I let it) and in water (gets on plane and runs WOT) but I constantly am adjusting the carb idle air screws to do so between different scenarios. Any ideas ????

 

[racerone]

Checked for missing bleed inserts ??---Low speed MIXTURE screws are to be adjusted with boat in the water and idling in gear.----Adjust ( rich ) till bogging goes away.

 

[Tripp Halbert]

Hey Racerone,

I have adjusted the mixture carb screws both in and out of water to maintain consistency. I feel like the screws themselves are rattling loose but I don’t know if that possible?

What are bleed inserts?

Thanks!

 

[racerone]

There are 5 bleed inserts.----Found when removing transfer port covers.----Not found on the bottom cylinder.----Tiny nylon inserts.----Often have gone missing.-----It should not be hard to set low speed mixture screws.

 

[Tripp Halbert]

Racerone,

Digging into this info and I don’t see a transfer port cover for my engine. I do see them for earlier models (1979). Maybe I’m mistaken?

Are these bleed inserts external or internal?

Setting low mixture screws has been challenging, it seems to be changing its needs when setting on hose vs in water

 

[racerone]

Good luck with your motor.

 

[Chris1956]

You cannot adjust idle mixture on a flusher device. It must be done in the water, in gear with motor warm.

Initial mixture setting is 1-1/2 turn open from seated. Run motor in water, in gear and warm it up. Now adjust mixture screws 1/8 turn open, to allow acceleration, one screw at a time, starting with the top screw. Test acceleration after each adjustment. You will need 6 or more "tests" to get mixture close to optimum.

As you richen mixture, idle quality will decline a bit. The goal is to get smooth acceleration, with a reasonable idle. If she idles well, you are likely set too lean.

 

[Tripp Halbert]

Thanks Chris, I will give this a try today.

 

[Tripp Halbert]

UPDATE: Hello all, so the maiden voyage was a success. I was able to get the carb mix screws tuned in good and we idled down the creek for roughly 10 minutes at 1000 rpms. We slowly started to get on plane and the engine began to bog. I had my lady pump the primer ball and the ol Tower of Power came to life! We ran it mid-range and hit WOT (during which primer ball went flat??) a couple of brief moments, ending the journey with a 2 hour boat ride as we idled alot just to let it run and enjoy the day.

I am going to get the fuel pump kit in and test again to ensure that is an issue as suspected. I will check back with updates.

 

[racerone]

If the bulb goes flat you have and issue from bulb to the fuel tank.----Problem with tank venting.----Or issue inside fuel tank.---Or issue with anti siphon valve if there is one.

 

[merc850]

Some tanks have filter on the pickup which might be clogged.

 

[Tripp Halbert]

Hello all! Sorry it has been some time but i finally got a chance to test ride everything. I installed a new fuel pump kit and the permanent 19 gallon gas tank at bow. Overall the ol' Tower of Power ran like a bat out of hell !!!!!!!!! (no ball pumping required by my lady this time around ) Low, mid, and high range running was all very smooth.

Only small issue i noticed was at long-term idle; the engine puttered nicely around 8-900 rpms but after letting it idle a while talking to a neighbor as well as getting the truck to the ramp, i would go to put in gear and it would sputter a bit and stall. Cranked right back up though no problem. Could it have just been loading up a bit due to conditions listed below??

Notes:

1. I previously set the 3 idle screws (successfully) but have since installed new fuel pump kit. Perhaps the new pump has changed the needs of the carb (different from current idle setting)??
2. I put 9.5 gals of non-ethanol fuel in (prepay) but accidentally put 10 gallons worth of oil in prior. Figured i would run it a little heavy anyways for the test.

 

[Tripp Halbert]

Edit for Admin: double post here please delete.

 

[racerone]

The wee little bit of extra oil makes no difference.-----Did you install a new impeller ?----Revisit low speed mixture adjustment.-----I do not believe there is a thermostat on these.---So local water temperature changes idle.

 

[Tripp Halbert]

Racerone, Yes new impeller a while back before ever setting her in the water (pee stream currently very strong). No T-stat on this model correct. Interesting point about the local water temp! Currently in Jax FL. it is around 60 degrees, could that be a factor? Will look into low speed adj. again, would you guess spin clockwise or counter ?

 

[racerone]

Have you found the transfer port covers on your motor ????----If not then good luck with it.