7.4L 454 Engine Start-up... Is this Normal?

[Sea_Ray_Seattle]

I purchased a '96 270 Sundancer a few weeks ago and it has a 7.4L motor in it with low hours (about 300 original hours). I'm curious to hear your feedback on these two questions:

(a) What is the "proper" start-up procedure for a big ol' carbureted V8 with electronic ignition?

(b) How long should it take to get the engine fired-up after having sat for a day or week?

The previous owner (and his shady mechanic) swore up and down that the following is the proper start-up procedure and how long it *should* take.

1. Full throttle down pump to open up choke
2. A couple 1/4 pumps
3. Then turn over engine while doing lots of 1/4 pumps
4. Let engine warm up around 1,500 RPM

It takes me about 20-30 seconds of solid starter motor to get some garbled starts out of the motor when doing the above. I do this 3 times and it finally starts-up, dies, and then finally stays on.

Is this normal? Any insight, tips, tricks are appreciated.

I've called a number of mechanics (albeit over the phone) they have said: Carburetor might need tuning, bad gas (gas is 6 months old), or carb needs a complete rebuild. The engine had a "tune up" when I bought it, but it was really just replacing spark plugs and changing filters and oil from what I can tell.

Last question - when under way, at 5 mph, I can sense very slight hesitations with the motor. Motor will run clean and smooth for a minute or so, then very subtle hesitations and RPM will dip from 1,100 down to 900. Is this normal? At cruising speed it's hard to notice it.

 

[Quint4]

The motor probably needs a tune-up. I have heard 7.4s like to eat spark plugs and I am starting to believe it. I just changed my 2 year old plugs and it made a difference (at least throw in some plugs). They are a little cold natured but not quite as bad as you are describing. A carb rebuild may also be in order. Perfect motor for your boat though...lots of torque.

 

[mwph]

I'm no expert and others will chime in with detailed suggestions for a fix but no way this is normal. 20-30 seconds is a long freakin time. Even then it dosen't stay running or run smoothly.

Did you have the boat surveyed? Did it act this way during sea trial? Has it (& the gas) been sitting in a slip for 6 months (or longer)?

Things you've heard so far sound pretty general to me. As far as the "tune up", the plugs may be a start but there is a lot more to be done. I'll stop here & let the experienced guys take over....



EDIT..............Quint - I thought about you & was hoping you would see his post.

 

[Captain Allen]

I've got two of the 454's and when they have been sitting a week or so, it takes a while for the mechanical fuel pumps to get the fuel pressure up. My practice is to turn it over for a few seconds, wait 5-6 seconds or so and do it again, and so on. Long turns are hard on the battery and starter. I let em warm up at 1200-1400 rpm's too.

 

[kpetry]

The fuel pumps have a check valve in them, which keeps the fuel from siphoning back down the fuel pump-to-carb lines and into the tank. If she sits for a while, and your check valves are not functioning properly it will take some time for the pumps to fill the lines and then top off the carb bowl. Depending on the topography of your fuel lines, it may even have to pull new fuel all the way from the tank - the farther it has to pump/pull fuel, the longer it will take for the engine to finally fire. I have a problem like this with one of my big trucks, but usually it has to sit for several weeks for it to be a problem. If yours does it more frequently than that, that's definitely "not normal". Your other symptoms of hesitation, etc, sound like a good carb cleaning and/or rebuild might help those.

 

[Sea_Ray_Seattle]

This is great feedback everyone, thank you.

Regarding the slow 5 mph "hesitations" I mentioned below, do you think that's also related to the carb needing a clean/rebuild? The gas is 6 months old in the tank, but it just seems odd that gas can go bad that quick. 1 or 2 years, definitely, but 6 months just seems odd. Right?

 

[Sea_Ray_Seattle]

I should have mentioned that I have a Mercruiser 7.4L matched to a Bravo 3. Not sure if this matters.

 

[kpetry]

6 mo old gas should be fine, assuming of course that it wasn't old when you got it. I'd be looking strongly at rebuilding those carbs. If you want to TRY the "cheap route", consider running some "Sea Foam" carb cleaner through the fuel system. It has a very good reputation for clearing up fuel/gunk issues. Many people swear by it.

 

[Quint4]

My 7.4 takes a few pumps of the throttle at first start of the day. Change the water fuel separator (dump it in a clear jar and see if it separates). A carb rebuild is not that big of deal and money well spent on a "new to you" boat with symptoms.

 

[Sea_Ray_Seattle]

Wow - problem solved. The prior mechanic decided it was a good idea to zip-tie the choke chimney. Zip tie was removed and it starts up great on the first try now.

Never ever go to "WP Marine" in Ballard if you live in Seattle. Just my $0.02.

Everything they touched they managed to screw up:
- Anti-fouling paint: fell off with pressure wash.
- Tune-up: yeah right, what a joke. Said that prolonged starts were normal.
- Wax: compound is still on 1/4 of the hull.
- Head: replaced a sewage line, now toilet won't flush.

 

[magster65]

Glad to hear your problem is solved... go enjoy a good summers boating now!

 

[Sea_Ray_Seattle]

Damn. I loaded up the boat with a bunch of buddies and turned over the motor. It took two tries and it was running well. Warmed up for 5 minutes and then launched her. After about 50 feet of back and forth gears (very tight space) the engine died. I tried for 10 minutes and couldn't get her restarted. Nothing worked. Tried no gas, full gas, nothing worked. Ugh. It's interesting though that at a cold start (had been 2 days since last use) it turned over fine, but when it was at operating temperature it wouldn't re-start.

Thoughts? What do you think, could it be a bad "choke stove" device?

 

[out-n-aboat]

1. look at the temp, make sure it is operating temp before proceeding underway
2. you may have flooded the engine

 

[Daddubo]

Your not running it out of the water are you? You are saying you loaded it up and ran it and then you ran it then launched it.:huh:

 

[Sea_Ray_Seattle]

The boat is in a fresh water moorage; I wasn't running it out of the water.

I checked the gauges before we launched, the temp was at normal operating conditions (warmed up for a solid 5-8 min before shoving off). I tried starting the motor a few times in neutral (no gas), then a couple times feathering the throttle at 1/4, then finally wide-open throttle. A few sputters, but nothing after that.

I think in the end I finally flooded the engine, but it just seemed really odd that at operating temp I couldn't turn on the engine while in neutral (should have been easier than when engine was cold... and when it was cold it was easy to turn on).

Choke stove? Other ideas?

 

[Daddubo]

Check the coil it might be breaking down when it gets hot. Pull the coil wire off and see if there is any oil on top of the coil or in it and check the tip for any cracks you can also ground the coil wire holding it about a ¼ in from a bolt with a pair of insulated pliers and check for a bright blue arc, if it’s orange it’s no good change it. If that is ok then pull the distributer cap off and see if there any problems there. If you flood the engine go to full throttle and try starting just be ready to pull it back real quick if it starts. I am taking it you changed the fuel /water separator. It also wouldn’t hurt to check the fuel filter in to the carb where the fuel line goes in.