1979 Mariner 90hp Inline 6 - No Start, no fuel

[rcwannab]

I picked up a project boat, motor and trailer for a self-education learning experience. It appears that the previous owner was in the midst of rigging this 1979 Mariner 90 hp in-line six engine to the boat and was far from done. I installed a fuel line from the gas tank to engine, purchased an installed cables from battery to starter, teased out and connected the control box wiring to the engine and installed new plugs. I can prime the fuel line and see some fuel drip out carbs. I advance the high idle and choke like crazy while trying to start. The engine spins like crazy, but will not fire. I took out the plugs and it seems that they are not getting fuel. I'm looking for suggestions on where to begin as I want see if this engine runs at all before I dig into repairing other issues.

 

[rcwannab]

The fuel line from the fuel pump tees in above the bottom carb (see pic) Is this correct? I found a parts drawing online that shows it teeing in at the top carb.
Would this have any impact on the issue? Thinking of rebuilding fuel pump and carbs?

 

[Chris1956]

Well that engine needs compression, spark and fuel to operate. I would check the compression first followed by checking for spark at the plugs. Does that motor have six coils or 1 coil and a distributor? The ignitions work differently, and 1979 was the changeover from distributor to six coil ignition.

 

[CharlieB]

If compression is good then the motor is worth taking care of. Spark test, if no spark then follow the directions in the CDI Troubleshooting gide for your ignition type, it contains both.

CDI Troubleshooting-Guide-Inside-Pages.pdf

 

[rcwannab]

Spark tester shows spark on all six. Will check compression. Thanks for the direction.

 

[rcwannab]

This engine is six coils.
Inline spark tester shows spark at all six plugs. Compression is 117 to 120 on all six.
Primed bulb, high idled and choked substantially, but it doesn't want to fire.

 

[Chris1956]

Check timing,. Set throttle to just open the carbs, ign key on. Remove prop and jumper solenoid, and read timing. Timing should be 2-9* ATDC.

 

[rcwannab]

Haven't had much time to work on it this week. I did remove the plugs and used syringe to inject mixed fuel directly. Turns over and fires, but won't run.

 

[rcwannab]

Had a busy couple months unable to work on engine. I did pull it out today as I have a bit of free time and noticed gas leak at bottom of the top carb. Appears to be fuel leak from the brass plug for the main fuel nozzle. What is best way to seal this?

 

[Chris1956]

Is the leak from the brass plug on the bottom of the carb? If so tighten it with a large screwdriver and clean it with a solvent and put some nail polish over it to seal it.

 

[rcwannab]

Yes. After disassembling and cleaning carbs and replacing gaskets, the brass plug on bottom of top carb is leaking fuel. Never would have thought of nail polish to seal.

 

[Chris1956]

Actually, the brass plug is a taper fit. It will seal the fuel in, when tightened. The nail polish will help (just help) to seal the air out.

 

[CharlieB]

When cleaning the carbs did you use spray can carb cleaner and spray through the idle passages of each carb? This is critical as they are very small and can clog quite easily, preventing a motor from starting. Carb soak type cleaners can often fail to clear these smaller passages. They do a greeat job cleaning everything else, but the spray type works well for these small passages. Best followed by compressed air but this is not an absolute as the better spray cleaners are very light solvents and evaporate readily.

I do NOT recommend any of the water based cleaners.

The old stacked 6 loves the choke to start. Some people keep pre-mixed fuel in a spray bottle and give each carb a squirt prior to cold starts to speed starting.

 

[rcwannab]

Soaked most and sprayed cleaner through passages followed by blowing with compressed air. Still doesn't want to start unless I spray premix in each cylinder, then it fires but no more...

 

[Chris1956]

Well, you still have dirty carbs, or the choke circuit is not working Are the two choke shutters closing when the choke button is pushed? Is the motor cranking at least 300 RPM? You need that RPM to help choke function correctly and make a good spark.

 

[rcwannab]

Thanks for the continued assistance. Yes, the two shutters are closing. Not sure how tight they are supposed to be.

The battery is brand new purchased a few weeks ago; group 27 with 750 marine cranking amps.

 

[rcwannab]

No Title

I am now getting back to the engine after a month away. I torn down the carbs again only to find them with gel/goo. I soaked and blew everything clean. Ordered new floats, needles and seats. Old needles were four sided (square) and new are much more round... I also removed the aluminum gas tank, dumped gas and cleaned as best I could.

I reinstalled the carbs and just pulled fuel directly from a small plastic can, pumped the bulb and noticed some gas coming from carb overflows then the engine fired for a bit and really pumped fuel out top and bottom carb overflows. Why is fuel pumping out the carb overflows when it fires? I'm thinking reinstall old needles? Or is it adjustment of the float, etc?

 

[Chris1956]

Stick with the new needles, seats and floats. The new needles and seats were a pair right? It is important not to mix new and old needles and seats, as they have changed over the years and are incompatable.

​I think you need to adjust the float height. Do you know how to do that?

 

[rcwannab]

Yes. 3 new sets of needles and seats (pairs).

No. I do not know how to adjust float height. Any input would be appreciated.

 

[jimmbo]

One thing you should do, That yellow hose... Plug it with a small ball. It is part of what Mercury called Back-drag carburation. It used metered intake vacuum to lower the atmospheric air pressure in the carb bowl, leaning the mixture under part throttle high rpm cruise. It worked wonderfully to help the part throttle fuel economy in the late 70s and early 80s using gasoline from that era. Gas today is different and with the oxygenators that are blended in the resulting mixture is too lean and can lead to engine damage. Plug it with a small ball. What you were calling "the overflow"... That is a metering jet that metered/controlled the backdrag feature. It can be left alone when the hose is plugged. It will ensure full atmospheric pressure is in the fuel bowl of the carb.

Adjusting the floats on those carbs has got to be the goofiest thing I have ever seen. Here is a link to how it's done

http://www.boatinfo.no/lib/mercury/manuals/mercury_1965-1989_40-115.html#/112