1979 Mercury 150hp intermitent poor running issue.

[BRIdaho]

Greetings to all, I'm the proud owner of my first river boat, WHAT A HOOT..... Engine is a 150hp V6 Mercury with a jet foot. I'm having two problems that are frustrating. The first is a hard start cold issue. Ive flushed both fuel tanks, tank vents are clear, Replaced all fuel lines on vessel. replaced fuel bulb, added a fuel filter system. The first start of every trip is tough, after that it fires every time during the day with no issues. Second issue is intermitent poor performance. It feels like the motor is starving for fuel, I have done nothing with the fuel pump and have no idea of its current psi output. I have heard that old Mercury's, 140 hp and up can experience fuel starvation issues. I have been told to add and elecric fuel pump in place of the fuel bulb. I have located an electric pump that puts out a steady 7psi. Any thoughts on the fuel pump and any ideas on the starting issue. Thanks for any advise...

BR
Idaho

 

[checkmate150]

Re: 1979 Mercury 150hp intermitent poor running issue.

Join the club... Mines an inline 150 with similar problems. I put an electirc pump in mine rated at 4-7 psi over the weekend and the boat wouldnt even rev up. Like it had just enough to idle. Put the old mechanical back on and it would rev just fine. Mines at the marina getting fixed right now. I think mine has an electrical issue, ive been through the entire fuel system and can't seem to fix it. When I find out my damage i'll let you know what they find.

Neil

 

[ENSIGN]

Re: 1979 Mercury 150hp intermitent poor running issue.

Try squezing the primer bulb when it runs bad and see if it smooths out.

 

[j_martin]

Re: 1979 Mercury 150hp intermitent poor running issue.

Don't try to run it when it's starving for fuel. The most common reason for a merc v6 burning down is fuel starvation.
That said, I got an XR4 discounted because it had problems. I'm an engineer, so I went after it with instrumentation, so I verified each fault and it's repair. They were:
Chit in the tank
Plugged filter (not visible, but several times)
undersized brand new aftermarket fuel line and primer
undersized brand new aftermarket bayonet fittings
fuel pump rebuilt with obsolete parts after current modification (disks were rubber, loose, and curly.)
floats set wrong
bad gaskets in carbs (had been "rebuilt" without all gaskets.)
timing off
linkage synchronization off.

All of the misadjustment and wrong parts problems were introduced by a "certified" mercury mechanic at a large dealership that shall go unnamed.

To be fair, I introduced one myself. When I changed the fuel lines to tygon, I put a tygon pulse line on the fuel pump. It won't work. It has to be fairly hard rubber hose.

That encouraged me to get educated, get the proper manuals, and go at it. Now this thing runs like a scalded dog.

hope it helps
John

 

[BRIdaho]

Re: 1979 Mercury 150hp intermitent poor running issue.

Thanks for the information.

Neil, Ive been told I may have electrical issues, I guess I don't want to believe it at this point.... electrical??..Let me know what they come up with..

John, I have purchased the SELOC manuel that relates to this engine, I have often wondered if the timing and adjustemnts on all linkages could be causing some of the issues. I'm worried about finding a Tech. that truly knows his business. Heard to many bad stories?

Happy boating and good luck to all..

BR

 

[Jacket4life]

Re: 1979 Mercury 150hp intermitent poor running issue.

BR-

They just got through lecturing me over buying the Clymer manual, they'll get you next I bet! LOL.

I'm shopping for a Merc manual now!

Will say that I used my Clymer manual to do my first lower unit yesterday, and it was pretty helpful. I don't think the specs are nearly as exhaustive as in the Merc maunual, though.

Can't help with your problem, good luck!

 

[j_martin]

Re: 1979 Mercury 150hp intermitent poor running issue.

Thanks for the information.

Neil, Ive been told I may have electrical issues, I guess I don't want to believe it at this point.... electrical??..Let me know what they come up with..

John, I have purchased the SELOC manuel that relates to this engine, I have often wondered if the timing and adjustemnts on all linkages could be causing some of the issues. I'm worried about finding a Tech. that truly knows his business. Heard to many bad stories?

Happy boating and good luck to all..

BR

Would I yell at you about your manual?

Might help to know who and where you are. Then you could either get direct help or a good reference.

Would also help if you would describe the symptoms you see in detail.

The starting problem might just be operator trouble. Took me awhile to figure out what mine wanted. Now, if after the song and dance it doesn't hit within 3 seconds, I check the kill switch. \

Link n sync is critical. It's a bit intimidating the first time through, and then you figure out what's what, and it makes sense.

 

[BRIdaho]

Re: 1979 Mercury 150hp intermitent poor running issue.

Learned today that I do have an ignition problem. Not getting spark out of plug wires on cylinder 3,4,5 at idle. Checked all plug wires and they have same Ohm readings, 10-12. What are the chances that both modules are bad. Top module runs cylinders 2,4,6. Bottom module runs Cylinders 1,3,5. In the automotive world, typically when a module goes out you loose all cylinders operated by that module.
My outdated Ohm meeter doesn't have the capability to perform suggested tests on coils...

Strange part to this problem is this.. While operating I have felt the motor either gain or loose performance intermitently. Have not been able to narrow it down to warm engine or cold engine operation. Today upon first starting with boat on trailer I learned the above. I have in the past put the boat in the water and ran it at low throttle until I hear and feel the motor start running on all cylinders, it will run fine for a while and then start sputting again. It comes and goes...?

I'm contemplating replacing Coils... atleast for the three cylinders that are not functioning.

BR
Blackfoot, Idaho

Update: Decided to swap coil #4 with Coil #2 to see if problem followed the coils. The problem did not follow the percieved bad coil. It worked fine on #2. After doing so and using an HEI automotive spark tester I have a bright blue spark on cylinder #2 during cranking. No spark at all on other 5 cylinders. I don't understand why I have spark on 3 cylinders at idle when I finally get it to start??? I do notice that while attempting to start it does act as though it fires/pops on one cylinder for some time before starting?

At this point I'm assuming my modules are bad or an issue with the triggering system....?????

Any thoughts??

Frustrated....
BR