1974' Mercury 150 hp inline 6 wont start - has at least spark

Hey guys, so my motor has spark and from what i can tell it has fuel as if i prime it i can see fuel dripping out of the carbs (the fact its doing that may well be a problem aswell??!! - maybe the carbs need a clean for a start, could squirt some carb cleaner into them?)

So when i turn it over its almost like theres not enough battery power to get up enough revs to actually fire - it comes across as very laboured (and thats using a fairly new 12v heavy duty), but if i take the plugs out and turn it over it turns alot more freely (which is to be expected as theres no compression without the plugs - but all pistons move freely)

im wondering if the carbs are blocked or fuel pump isnt working, coz if i squirt enginestart into the cynlinder and then turn it over it, you can hear if fire then its like the battery runs outa juice adn it goes back to sounding laboured....

another question, does it have to be in neutral before it will start??

To start it i pull the choke lever all the way forward (advance timing lever on the controller), then hold down the choke button adn then turn it over???

as my controller was in bits (i put it back together with a parts diagram), it never seems to go into neutral, without the controller whats the easiest way to get it into neutral?? just

I know this is alot to take in, and very vague, but any ideas as to where to go next would be great, been a 2stroke there cant be that much wrong - or im doing something wrong, theyre fairly simple motors, any help would be appreciated

Re: 74' Mercury 150hp inline 6 wont start - has at least spark

First report the compression #'s---------------------Will spark jump a gap of 7/16" on all six??.--------------Is the timing belt on correctly ???--------Is the starter motor in good shape ( tested and inspected)--------------Spraying a bit of carburetor cleaner into an outboard is a complete waste of time , they need to come apart to clean all the passages and jets INSIDE the carburetor !!

Re: 74' Mercury 150hp inline 6 wont start - has at least spark

The other item you need to check is ALL of your electrical connections. What may appear tight could be corroded. I would remove each power connection, lightly sand the contact and re-install.

It is not beyond the thought that the starter may be going south too. I have had that happen that a starter would spin-up w/o load and die when plugs were installed. The solution is a starter re-build or replacement.

The easiest way to insure you are in neutral since you are in the early stages is to remove the shift linkage and do it manually.

A secret to starting an inline is to have it mounted on the stand or transom and have it fullt tucked in. The fuel if it leaks from the carbs should flow back into the block. You can get a small pump oil can and fill it with 50:1 fuel and squirt a shot into each carb. Yes, forget the carb cleaner and NEVER starter fluid.

If you get to whits end, send me a PM and I will give you the contact info for one of the best inline people I have ever encountered.

Re: 74' Mercury 150hp inline 6 wont start - has at least spark

The OMC built ----" primer injection unit " ----------can be installed on the early inline 6 and guarantees an end to troublesome starting on some of them.------Slow cranking may mean a no spark condition.