Check the electric choke

 

I had a 350 once that was hard starting and it turned out to be a problem with the mechanical advance in the distributor.

 

I replaced the Mercury Thunderbolt Ignition with the Davis Unified Ignition from Performance Distributors in Memphis, TN earlier this year and noticed faster starts on my boat. It was easy to install, and greatly simplified the boats ignition system.

 

If you're running a QuadraJet....they leak some fuel while sitting. After sitting a week, the fuel pump needs to fill the carb so you'll crank for that long before she fires. After sitting only an hour or so (after a run), it will leak enough that it is easy to flood the engine. Don't add fuel when trying to start....leave in neutral and don't pump the throttle. My 1990 454 acts like this and it's not a real big deal but can be fixed when rebuilding the carb, Mike.

 

all sound like reasonable reasons, as it fires best when I DONT pump the throttle before starting.

Patokapirate-
Do you have any additional information about that ignition system (where did you purchase, how expensive, how intensive of a job to do?). I was thinking about going through the ignition system at the end of the season (wires, distributor, etc.) but never heard of the Davis system????

Thanks for the replies guys

 

The entire system was about 350 bucks. You order from the company. They set the unit up for your specific application. They will ask what your boat weighs, grade of gas you use, if the engine is stock or has performance mods. Answer the questions and make sure you tell them it's for a boat. They have a website and there are several stories on the web about people installing them. I found out about them on a different boating site. Google "Davis Unified Ignition".

As for the install it was as easy as switching distributors. Their system is all in the distributor. I hooked up the purple ignition wire from the + side of the coil to the power terminal of the Davis unit. The grey wire on the - side of the coil gets hooked to the Davis unit's tach connector. I switched to autolite 145 plugs, gapped at .055 and used the stock plug wires. I trimmed off about half an inch of the plug boot at the distributor end to make them go on the new distributor better. If your wires are old though consider replacing them as well.

 

I just ran into same problem with my 7.4. rebuilt carb. Thought maybe bleeding over as other post said.Thought ethanol was boiling out nope.Had good fuel pressure. Went to ignition pickup in distributer was corroded .Even though boat ran fine once started it looked terrible cheap to replace nope.Mine ended up being starter just not spinning hard enough to really fire motor once hot.I got a brand new with warranty off eBay for 55$ couldn't believe it.Starts like fuel injection now.

 

My previous boat ('89 340DB with Gen IV 7.4s with Rochester Quadrajets) had the same problem. I replaced all the ignition components - coil, wires, dist caps, plugs, ignition amplifier (thing inside the dist). Didn't make much of a difference. After rebuilding the top end on the stbd engine (heads redone, carb rebuilt), some impvt but not much. Just a quirk of the motors I guess. BTW, you probably don't have electric choke. A small coil on top of the exhaust manifold heats up as the intake manifold warms and opens the choke.

Difference btwn your problem and mine is that you get hard starts when warm too. Both motors started with the slightest touch of the ignition switch when warm. Replace all the ignition components to establish a baseline and go boating!

 

Try this. When your boat is cold start it. As soon as it starts shut it off and restart it. If it starts right away it is a fuel problem. Most likely empty bowls.

Pete

 

Sounds odd to have a hard cold and warm start issue being fuel. Do you notice that is smokes alot when you first start it both warm and cold?
Generally the Qjet well plug leak takes some time to leak enough fuel to create an extended crank problem. Ron is right that you shouldnt have an electric choke, but a thermal spring located on the SB side of the carb mounted to the intake manifold.
I can say that my 7.4s take around 15 revolutions to finally fire after about 5 throttle pumps.
Idle mixture screws can cause a rich running carb which you should notice smoking and fuel smell on start up. When was the last carb rebuild? If it's been a while, thats where I would start after I verified that the cranking speed was sufficient.
Is it the Thunderbolt 4?

 

I don't know if it is a Thunderbolt IV or not. I have only had the boat since last Sept, and it runs great, no lapse in throttle response, idles fine, and I can troll in various small increments of throttle positions without the motor skipping a beat. The only issue is when I go to start it, it behaves as though it is flooded and it doesn't seem to make a difference if it's hot or cold, both instances take mulitple tries to get it to turn over. Smells of gas at first start, and if I do try to manually engage the choke throttle, it starts even harder. The best way is for me to give it one initial "squirt" of fuel, back it to the neutral position, then crank on the starter for usually 2 to 3 times, but each time I have to keep the starter engaged to the point the motor is practically turning over/running before I can go to the "on" position on the key. Im afraid I am going to burn out my starter. It sounds like the starter is engaging with a good speed (cranking), but I don't know how to measure/verify for sure. Both batteries are new and don't notice any noticiable difference when starting with shore power vs. batteries only (to rule that out). Thanks for the ideas

 

If I wanted to have the carb rebuilt at the end of the season, is there a place I can send it to to have it done (remove carb and ship to have it rebuilt)?

 

Find a shop near you and take it in. It'll run prob btwn $150 and $250. No need to ship it off. If you have those boat shopper magazines you find in supermarkets look in the ads in the back. You'll find a guy.

 

Is this something new, or did this always happen? Have you ever tried starting without pumping? In theory, if there is fuel leaking into the intake manifold, you shouldn't need the initial "squirt" to get it to start.
You can also read your spark plugs to see if they are black and sooty on the tips. If they are, chances are that it's a really rich mixture.
Quadrajet is very easy to rebuild, with few special tools. I'm not sure what someone would charge ( I do my own), but I would bet that if you checked around with folks at your marina someone can rebuild it. You can buy a kit for about $30 and Berryman chem dip at a number of location to soak the carb.
Make sure to inform whoever rebuilds it about the issues you are having, so they can be sure to check for leaking well plugs.

 

I paid $225 to have mine built...then the boat sunk :.-(