My 1974 Mercury 150hp Hard Starting Issues

[Matt129]

Hello everyone, I have a 1974 Mercury tower of power 150 hp that is hard to start. Once it starts it runs beautifully but to make it start I have to squirt 2 stroke into the air intake of the carbs. This motor has been sitting for who knows how long and I still haven’t ran it much myself (only about 30 seconds to a minute at a time) because the impeller needs to be replaced so this issue might clear itself up once I’ve blown the cobwebs out of it so to speak lol, but if the issue doesn’t go away what in the carb would be causing it? Thanks.

 

[racerone]

Install an electric primer valve as found on Johnson / Evinrude motors from 1980 to 2005.----Simple and reliable.----Squirts fuel into the motor like you are doing now.----Does it at the push of a button.-----Lots of good used ones available.

 

[Chris1956]

Do the two choke plates close? You can adjust the plastic gratings a bit to help them seal the carb throats better. Not too tight so they bind however.

Make sure the battery cables are clean, as the faster the starter spins, the better choking action.

On that engine, pump primer hard, cold start all the way up, hold choke button down and crank until she fires. Once she starts, "feather" the choke until she runs well. Fresh 50::1 fuel helps idle quality, a lot.

Poor cold start is an idiosyncrasy of that motor, which is why later models went to enrichers.

 

[racerone]

The Johnson / Evinrude primer will make hard starting a thing of the past.----Time to take starter apart as well.----Slow cranking is also an issue on these wonderful motors.

 

[Matt129]

The Johnson / Evinrude primer will make hard starting a thing of the past.----Time to take starter apart as well.----Slow cranking is also an issue on these wonderful motors.

Oh the starter works fine and cranks good. This motor is going to be… interesting once I’m done with it to say the least . It’s going to have an Evinrude primer on it and a special ignition on/off toggle switch on it because for some reason the key won’t put power to the switch box but still cranks the motor, so I’m just going to wire a jumper switch in between those wires that goes to a toggle switch . I’ve already tested, it’s going to work. I just feel bad for whoever opens the engine someday in the future if I ever sell it and wonders what the heck is going on lol. Btw do you actually think these are wonderful motors or were you being sarcastic? I’ve heard it both ways, some people love ‘em, lot of people seem to hate ‘em . Also the choke does work just fine. How would I find a primer assembly that would fit this motor? Whenever I look it up all I get is primer solenoid rebuild kits lol.

 

[racerone]

The inline 6 is a wonderful motor if in good condition.----As stated some folks think they are junk !------So good luck with it.

 

[Scott Danforth]

Matt, have you taken care of the wiring issue you had in your other thread?

since this motor sat for a long time, did you clean the carbs and do a link-n-sync?

 

[Matt129]

Matt, have you taken care of the wiring issue you had in your other thread?

since this motor sat for a long time, did you clean the carbs and do a link-n-sync?

I’ve gotten it all taken care of, all it needs now is a water pump impeller and one of those Evinrude primer units and it’s out on the water! Does anyone know the specific gas oil ratio to use with these motors? I don’t want to burn it up lol. And where can I find one of those primer units? I can’t seem to find a complete assembly online.

 

[racerone]

Lots of those primers on E-bay.---I suppose I should list all the one I have on there.-----They are not hard to find.----And no I am not sarcastic at all.----I can be blunt and to the point.----Sometimes the simple stuff is not well understood.----Sorry.

 

[Matt129]

Lots of those primers on E-bay.---I suppose I should list all the one I have on there.-----They are not hard to find.----And no I am not sarcastic at all.----I can be blunt and to the point.----Sometimes the simple stuff is not well understood.----Sorry.

I have an old 12v inline car fuel pump, with a little bit of Jerry rigging do you think that would work? It’s not one of those types that sit down in the tank, it’s one of those old clicky clack types that would sit on the motor and suck from the tank.

 

[racerone]

The Johnson / Evinrude electric primer is a valve.----It is NOT a pump !!

 

[Scott Danforth]

I have an old 12v inline car fuel pump, with a little bit of Jerry rigging do you think that would work? It’s not one of those types that sit down in the tank, it’s one of those old clicky clack types that would sit on the motor and suck from the tank.

So you want to create a bomb?

 

[Matt129]

The Johnson / Evinrude electric primer is a valve.----It is NOT a pump !!

So you want to create a bomb?

I’m confused. I was under the impression that the primer would squirt fuel into the throat of the carb? At least that’s how my 8hp Evinrude works. If I wired it to a push button, let it squirt some fuel into the carb throat and then turn it off and start the motor, how would that be different then a primer? I wouldn’t have the actual pump in the motor casing, it would be mounted near the trim pump with a tube going to the carb throat, I don’t see how that would be different then me having to go back there with a squirt bottle and tearing off the cowling so I can get at the carbs like I have been doing to test it.

 

[Scott Danforth]

automotive fuel pumps do not need to meet SAE J1171

an electric primer only opens an orifice to allow the engine's existing fuel pump to put a really small amount of fuel into the air stream.

an automotive electric fuel pump will shoot way too much fuel into the carb, and either the back-fire from the engine will cause the boom, or the fact that the fuel pump isnt spark suppressed will cause the boom.

you still have not cleaned the carbs from the engine sitting for years.

 

[Chris1956]

That motor runs on a 50::1 gasoline to oil mixture. Mix 1 pint of TCW-III two cycle oil to 6 Gallons of gasoline.

Gee, those motors take a few extra seconds to start when cold. They start instantly after the initial start. Why do you want to change the choke to a primer? The choke worked adequately on millions of these motors for 20 years. Learn how to properly cold-start it and go boating.....