Can I save my 72 Merc 115 with scored cyl walls??

[willienelsonjr]

Long story short: my, new to me, 1972 Merc 115 (1150) is cutting out at top end after running for 30-45 seconds. Starts hesitating and sputtering. Will run at 1/2 -2/3 throttle ok. Jumps back when bulb is pumped. Both fuel pumps have been rebuilt. Mechanic scoped #1 cylinder, said the walls are scored. Past owner "hurt" it at some point. Says I need to rebuild, or just get a newer 4 stroke. He says it will not get worse, but will not get better. Seems like a very knowledgable mechanic.
Can I salvage this motor? Is there and addative that will reduce the scoring (i know it is a 2 stroke, and that may be a 4 stroke thing)?

The max motor on my boat plate is a 115. The boat is a 24' pontoon. I am in Colorado and run the boat at 5700 feet elevation.

 

[jimg984]

Re: Can I save my 72 Merc 115 with scored cyl walls??

you say good mechanic,, did he do a compersion test on all cyls? all cyls should be within 10-15 lbs of each other low end of comp 90 high end 140 if all are with the range 10-15 low end 90 up use it and enjoy it

 

[jimg984]

Re: Can I save my 72 Merc 115 with scored cyl walls??

sounds like a fuel supply problem (dont think that motor has 2 fuel pumps) could be a clogged screen on the pickup tube in the gas tank, bad fuel lines. fuel lines is one of the cheapest thing a boat owner can do for them selves and most often overlooked,,, if 1 hose is bad replace all of them.

 

[willienelsonjr]

Re: Can I save my 72 Merc 115 with scored cyl walls??

Thanks for the input jimg984. I meant fuel pump, he had me buy only one rebuild kit.
He did not do a compression test. The boat is moored and he was working on the water. I gave the benefit of the doubt. Sounds like I should do a compression test before giving up on the motor.??
I replaced the main fuel line last week, do you mean the fuel lines under the cover?
He said the scoring would reduce the compression, which affects the fuel pump as it works off the "down stroke." He used a different term. That sound right?
Again, thanks.

 

[willienelsonjr]

Re: Can I save my 72 Merc 115 with scored cyl walls??

Update--ran it this weekend. Ran ok with full tank at start of day. as day went on and take ran down, it lost all power. could not make RPM's and maybe 5mph. Ran a little better if i pumped the bulb. bottom line, runs worse and the tank lowers and the day goes on. Limping back to the marina. HELP!!!

 

[Chris1956]

Re: Can I save my 72 Merc 115 with scored cyl walls??

If pumping the fuel primer bulb helps, you have a weak fuel pump(or pumps), slightly clogged fuel filters or a clogged vent in the gas tank.

Does that motor have the round paper filters under the carb top covers? Does it indeed have the two small fuel pumps on the transfer covers, and the "round robin" fuel line? or does it have the single fuel screen and pump unit on the bottom starboard side of the lower cowling? the single fuel pump was marginal at best. make sure all the gaskets are new and airtight.

A compression test will tell you if you need a rebuild. it may be cost prohibitive, if you cannot do the work yourself.

 

[willienelsonjr]

Re: Can I save my 72 Merc 115 with scored cyl walls??

Update-Took it to another mechanic. He did say a compression leak down will ID the problem for sure, but not fix anything.
Two small fuel pumps on the side, one halfway down, second at bottom lined up with #6.
The carbs were rebuilt last summer, boat fires right off, stalls when choked (not running lean) and runs best cold, full tank, or if bulb is hand pumped.

Mechanic #2, whos is well known around here, recommended just cutting to the chase and installing an electric fuel pump. He is backed up for 2 weeks, but took time to show me how to do it.

-bought a small low pressure electric pump at NAPA 1.5-4psi
-installed by fuel pumps on right side, before the pumps, in-line
-ground to existing screw
-Powered to white lead on the power pack, on with engine power
-mounted pump to side of motor on existing bolt
-runs great now, lake testing in am.

Seems like a jerry-rigged fix, but for the $50 and 2 hours install, it seems like a great solution. Hell, if it runs, why worry? According to the mechanics, the motor will not get worse (unless i abuse it), so now it can have the fuel it needs.
Will give update after lake test.