So close, so far away, merc 1150

[biggjohnjeremy]

OK so I'm starting a new thread. I had some I'm put from yall on my 1978 mercury 1150 115hp online 6. I bought it not running, they said it needed a carb rebuild. So I rebuilt the carbs with some input and the manual and also replaced water pump and impeller. Along with some fuel lines.. anyways it started last night on the hose and sounded great. I decided to take it out to the water today to see what happened and it started in water with little trouble. I put it in drive and took off!! Everything was great and it was running like a dream, then after about 5 mins, sit started losing power and subsequently died. I had a really hard time starting it back up and when I did I had to use neutral throttle.. once it started I could normally keep it in neutral and it sounded like is was struggling to stay running. After it was running it would die every time when I put it in gear. I could only get it to go if I revved it high and dropped it in gear. And it ran terribly. I was hoping someone could give me ideas on where to start. Thanks

 

[Chris1956]

First take a spark test and a compression test. If those are good, I suspect you have dirty fuel. clogging up those clean carbs you had.

 

[biggjohnjeremy]

Ok, I will give that a try. When doing compression test, do you need to remove all housing to get to number 6? I couldn't even get my spark plug wrench down there. Or it there a trick in not sure of?

I just dont understand how it could have been running so great and then it just starter falling on its face. It seemed to me that it started missing on 1 or 2 cylinders.

 

[biggjohnjeremy]

I just dont understand how it could have been running so great and then it just started falling on its face. [/QUOTE]

 

[racerone]

Serial # of your motor must be posted.-----There are many simple things that will stop a powerful motor.---------Hole in a fuel pump diaphragm-------Cheap plastic tanks.----Water in the fuel.-----------No oil mixed with the gasoline.-----Bad / leaky hoses.----------Dirt in a distributor cap if so equipped.-------I can not inspect all these things for you , I am too far away.

 

[biggjohnjeremy]

Thanks for your response, my serial is 4857753. I think it's a 78 merc 1150. It has a blue distributor that I haven't looked into or tested. I just got fuel pump rebuild kit in today, so I will get that installed this evening. I bought some gas from a gas station I don't normally use and mixed 50:1 right before I took it out. As a side note I just ran the fuel line into a regular gas can because I wasn't done cleaning the one that came with the boat. It worked fine on muffs and also ran great for about 200 yards Before running like hell

 

[racerone]

They all sound powerfull and really nice when running on muffs.----Bark, bark , just wonderful.

 

[merc850]

Who said "all it needs is carb work"? Some sketchy owner or a young mechanic who wasn't born when the motor was made! People say all kinds of things when they're selling - anyway- check the distributor cap for center contact and corrosion/water and if you suspect the ignition (which I am) put a timing light on a wire when it stops and see if you have spark. You use a 13/16 open/box end wrench to access the lower plug.

 

[biggjohnjeremy]

OK so I have some things I did today and was hoping to get yalls feedback on. Since the half successful trip yesterday I installed a new gaskets and diaphragm to the water pump and gave it a good cleaning. Then I went through and did a cold compression check with wide open throttle. I got a reading of almost exactly 80 across all 6 cylinders. So then I put about 4 ounces of seafoam in a gallon of 90 octane non ethanol gad mixed at 50:1 and ran the motor for approx 10 mins. This motor normally smokes a little, but was much more smoky as it ran that gas. It also didn't idle great, it would vary rpms (I think due to what sounded like certain cylinders chiming in and out) but regardless it ran in neutral. So then I shut it down and pulled all plugs and grounded them to the block and took another compression test. It came back with about 86 psi across all cylinders.

I don't know what to take from it. I borrowed the compression tester from my local auto zone. Could it be just inaccurate because it is more suited towards automobile use? Or is 85 psi across the board a symptom or something? From what I've read on here is that it should be 100 or more. .
Also when I had the plugs grounded on the block I saw decent spark from all of the plugs.

Merc850, could you elaborate on what you meant earlier about the distributor test and timing light test?

Any ideas would be much appreciated!!

 

[biggjohnjeremy]

I didn't mean to say water pump earlier,.. I meant fuel pump. Also I have a video of it running from today I want to post here for imput. YouTube link the best method?

 

[wn6ngp]

Compression auto vs marine gauge is no different. Your reading sounds low but it is consistent across the cylinders so I'd think its ok. Are your plugs fouled? If they are not dark oily black then I don't think that you have an ignition problem. I know you rebuilt the fuel pump but you should recheck. It is possible to put those fuel pumps back together incorrectly and the motor will kinda run. I know I did that on my 90hp. I got one gasket and a diaphram out of order and I got similar results to what you are describing. Does the bulb pump up and stay firm? Once I got the fuel pump gaskets/diaphrams in the correct order it ran like a scalded dog.

Be careful about reving up in neutral and slamming into gear. My friend did that and twisted off the tail end of the crankshaft.

Good luck and keep us posted.

 

[biggjohnjeremy]

Well I'm hoping that the gauge was just a little inaccurate because it was only showing compression in increments of 10psi per tick mark. But the plugs looks pretty good and clean. They where just a little wet when I first pulled them and had a little brownish stuff on them on one side of them. I can take pics later and post them. From what I saw when I opened the fuel pump there was a diaphragm sandwiched between 2 gaskets. And only one orientation. So I put new ones on as they were take off and cleaned gasket surfaces. The ball is decently firm when running and squeezing it doesn't affect the way it runs. Lemme see if I can upload this video to YouTube and post link here. Thanks

 

[merc850]

When the motor dies put a timing light on Nr.1 wire and turn the motor over and see if the light lights, if not then this could be a trigger problem; if it flashes then it could be fuel related. Take the band off and look at the condition of the cap because you say that "I think due to what sounded like certain cylinders chiming in and out", if I have a condition like that I run it at night and look for arcing plug wires. I bought a motor last year and the carbon contact in the cap was missing and the lead from the coil looked good but was jumping the spark to the carb! You have to go over an older motor thoroughly and address all the potential PO "repairs".

 

[biggjohnjeremy]

https://youtu.be/x1DhwzYBWuc
There is the video of it. Lemme know what you think. Thanks

 

[wn6ngp]

It does sound like one cyl in missing periodically. Does it have a distributor? Good suggestion mentioned before, start it up at night and then look for arcing. I am surprised the plugs aren't fouling. Other thing you can try is disconnect or ground each plug one at a time and find the one where it makes no difference whether its connected or not. Then trace that wire back to the distributor, power pac or whateve.

 

[merc850]

The tilt is too high for proper idling - put it vertical and run again.