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454 issues plugs idle WOT

C

carech

Member
"All,

This is my first post

"All,

This is my first post on this site, which has been a great knowledge center. Firstly, my boat is a 1988 Tiara with twin 1988 454 Crusaders with approx 800 hours each. The port motor runs fine up to WOT 4200-4300, but I've recently been having trouble with the startboard motor... it's gone from achieving WOT 4200-4300 to just 3600.

I'm trying to connect the dots, so here are some other issues it's having:
1) Throttling up - ever since I've owned the boat, the motor bogs down around 2600-2800. If you keep pushing the throttle, it recovers and tachs up fine. My mechanic has felt it is a carb adjustment / transition issue.
2) Idle - seems to "lope" more than the other motor and the tach dances more. There is some noticeable white smoke and a small amount of petroleum in the exhaust water.. not sure if it's fuel or oil.
3) Plugs - pulled the plugs MR44T (picture below).. they look awful and #7 plug seemed wet when I pulled it and smelled like fuel. I replaced the plugs this weekend with MR43Ts and idled it for 15 minutes.. It fired right up and sounded pretty good, but was still smoking. Checked a few new plugs and they were starting to get black and #7 smelled like fuel again.
4) Temp - this starboard motor always runs cooler for the 1st 30 min than port.. takes a long time to get up to 160 degrees.

I'm wondering if this motor is running on 7 cyls... I never changed the plug wires and they look in decent shape. This has a Mallory dist with points and those were changed back in March. Checked cap to make sure firing order was correct and it was. Carb was rebuilt, new fuel filters back in March. Don't know how compression is... Any suggestions (i.e. valve job, timing advance)?
294233.jpg
Plugs
 
"Pretty clearly, you are runni

"Pretty clearly, you are running rich on all cylinders. Is the choke wired open, or at least, opening fully when warm? Stock carb and pump? Who did the rebuild?
If the dist cap is > 2 years old, replace it and the rotor."
 
Carb was pulled by a reputable

Carb was pulled by a reputable mechanic and he sent out for a rebuild at a local carb shop. It is a stock quadrajet and appears to be stock mechanical pump. Cap and rotor are most likely over 2 yrs old. Forgot to mention this boat sat in the yard for 2 years before I purchased it. How do you remedy a rich condition?
 
2 years of non-start? How mu

2 years of non-start? How much fuel was still in the tank after the 2 years? Was it flushed out? What filter does the boat have before the fuel pump?
You need to verify the choke opens completely.
 
"Tanks were full of fuel -- 40

"Tanks were full of fuel -- 400 gallons. Instead of draining it, we treated with startron. My mechanic then had me run it through new sierra fuel water separators down to about 1/3 full, then we added fresh fuel. There really wasn't much water in the fuel and the boat is now on it's 3rd round of fresh fuel. I must admit, I wanted to do the whole drain the fuel / polishing stuff... not sure if there are any residual effects of not doing this.

I'm not sure how to verify if the choke is operating correctly. I just know it's a manual choke."
 
"Manual choke would be very un

"Manual choke would be very unusual. From the factory, there is a heat/riser mechanism from the intake manifold. YOu would best remove the flame arrester and insure the choke plates are fully open when the engine is warm.

AND, running 300 gallons of 2 year old gas is impressive in itself!"
 
My mistake -- it does have an

My mistake -- it does have an electric choke. I'll look in my Crusader service manual to see what you're talking about and give it a try.

I am glad all that old gas is gone! The motors didn't seem to run any different with the old vs new gas.
 
"I agree with Dave. The choke

"I agree with Dave. The choke mechanism could be rusted up, preventing the choke from opening fully. You can wire it open for a test run. The distributor advance could also be sticking, causing poor high speed performance and an irratic tach. I have experienced the latter, as well as a shorted out ignition wire. Therefore check all wires carefully, and if in doubt, install a new wire set. Also agree that burning through 300 gallons of 2 year old fuel is most impressive! And not because of possible water issues, but because stuff they call "gasoline" these days start breaking down in as little as 3 months..."
 
"Plugs always look like that a

"Plugs always look like that at idle only. Run it down the river hard and they'll lighten up.

You need to verify that the choke opens ALL the way when hot. Pull the flame arrestor and compare with the other (cold) engine.

To see if she's running on all 8 cylinders, idle the fully warmed up motor at 1,500 rpms. Then, using insulated pliers and heavy gloves, pull then replace each wire in the distributor cap. The motor must slow then pick back up as the wire is replaced. And pay special attention to # 7.

Jeff"
 
"If it has an electric choke,

"If it has an electric choke, it has either been modified or the OEM one changed out. Jeff's observation that they all look like that at idle is, sadly, true - but they don't have to. If the choke opens, I'd ask the shop that rebuilt it if they replaced the float (many do not) and what they set the float level at.

The OEM carbs are usually tuned on the rich side; if you have the patience, you can get it dialed on for your hull. You can eliminate the sheen in the exhaust as well as the 'excess' fuel odor, too."
 
"You may have a bad needle val

"You may have a bad needle valve/seat. This spring I had a rebuilt carb installed on my '86 Tiara and it ran fine. For some reason I looked down the carb at idle and gas was free flowing down the carb through the primaries. Again, it was running fine. After 15 minutes my plugs looked just like yours. Rebuilt my own carb and replaced plugs and ran the rest of the summer and the plugs look like the day I put them in. I sent the old carb back and they said it was a defective needle valve/seat. I never put it back on so I don't know if they were right or not. Anyway, start it up again and look down the throat of the carb and see what it is doing."
 
"Thanks for all the input. Th

"Thanks for all the input. This weekend, I'll warm up the engine and check to make sure the choke is fully opening & see if gas is free flowing down the carb at idle. Also, may attempt pulling plug wires one at a time per Jeff's suggestion. Will let you all know how it goes."
 
"One more (another!) t

"One more (another!) thing you can try is this:

To see if the carb is flooding, warm the motor thoroughly and turn one idle mixture screw in until it GENTLY seats. (Count the turns so you can back it out to where it was before.) If the motor slows or tries to stall when you do this, the carb is okay. But if it keeps running, or speeds up, it's flooding.

Jeff"
 
"Will try this too. Also, I d

"Will try this too. Also, I do have an infrared thermometer. Instead of running the motor at 1500 and pulling each plug.. would it be possible to check temp readings around each cylinder before things got too hot and locate a possible dead cylinder in this manner?"
 
"Chris, You would be better of

"Chris, You would be better off actually hearing the engine respond to the pulled sparkplug wire...you will know for sure. Besides, if you get ZAPPED, it only take about 30 minutes before the muscle spasm in your arm can relax.

Only kidding, just do what Jeff said !"
 
"Two additions:

1) if y

"Two additions:

1) if you opt for the "pull the wire" test AND you have a qualified helper, you'll find this test much more conclusive if you can do it underway. Those 454's make lots of low end torque and loading them makes the miss/lack of very easy to discern.

2) if you see raw fuel in the primary bore, note if it is one or both - a ruptured fuel pump diaphragm will cause raw fuel in the primary bore where the sight tube fitting is bored thru."
 
No fuel pump - the excess fuel

No fuel pump - the excess fuel delivered to the carb via the tygon "sight tube" that is right above the fuel line nut on the carb.
 
from your pic of the plugs the

from your pic of the plugs they all looked equally bad. If you had a dead cylinder wouldn't that plug look new? If the plug wasn't firing you would have no combustion therefore no carbon right?
 
"Well every now and then I chi

"Well every now and then I chime in with some of my experiences which may or may not be applicable to anyone else's situation. "Lope" is something I have experience with. My starboard engine (454 CID) loped for many years. After the engine warmed the loping stopped. Turned out to be the choke took an awful long time to open fully. Someone on this forum suggested wiring the choke open. I did and no loping now. I really don't seem to need the choke because I keep the engine compartment warm. On the coldest of days I can just visit the engine bilge and take the wire off.

It was a good suggestion for me. The other thing I found is that crappy gasoline results in fouled plugs. I roughly get 30 hours on a set of plugs burning bad gas. Since learning that lesson, I never fill my tanks. I just deal with the condensate in the tank.

Chuck Hanson"
 
"Again, all good input. I&#39

"Again, all good input. I'm chompin at the bit to check the choke and pull some plugs while running. Even have some insulated plug boot pliers so I don't get zapped!

I boat in FL, so wiring the choke open could be a good solution, if it's causing the problem."
 
"A quick update..

First, m

"A quick update..

First, motor started right up... However, this motor takes a long-time to warm up... 20 minutes.. just to get to 145 degrees. By then the choke had opened up 3/4 of the way. I pushed it open all the way and it stayed there.. seemed to be idling a little faster / steadier. However, still a lot of white smoke and fuel in water. I did take a zip tie and wire it open, which seemed to pick the idle up 300 rpms..

Also, looked down the primary bore and noticed fuel dripping very quickly down the left side bore and could smell a lot of raw fuel.. I could barely see the fuel in the right side bore, so it was a noticeable difference. Is this normal? Per my original post, I do have a plug on the left side that always smells like fuel when I pull it.

I didnt have a chance to do the pull the plug wire test or adjust idle mixture screws...

Also, another thing I noticed using my infrared thermometer.. it took motor 20 minutes just to get to 145 degrees at the thermostat housing.. i used the gun to check temps on the exhaust components and noticed much different readings too.. both manifolds were 160 degrees, left riser and elbow 130 degrees... right riser 128 degrees and elbow 103 degrees.. is this variance normal?

Thoughts? Not sure if any of this is related..."
 
"Exhaust system temps seem abo

"Exhaust system temps seem about right, but taking that long to warm up is not. Start by replacing the thermostat. The dripping fuel looks like carb flooding. Try that test of mine next time, after the t-stat issue is resolved.

Jeff"
 
"You shouldn't have to mov

"You shouldn't have to move the choke to get to full opening. The linkage is dirty/worn/binding or the coil is old and weak and needs to be renewed.

The primaries should look and behave in a similar manner. what you described is not normal and is consistent with a flooding problem. You may want to get a whiff of the dipstick, too. If that is gassy, time for a change. That aft lowest plug being wet indicates the issue is rather severe so I would address the flooding pronto.

The wire test will only confirm #7 isn't firing. I doubt the mixture adjustments will remedy the flooding."
 
My regular mechanic was workin

My regular mechanic was working on the boat next to mine today and took a look.... we pulled a few plug wires at 1500 and it was tough to detect whether or not number 7 cylinder was firing. He was pulling plugs bare handed off the distributor and noticed that the spark was very weak... barely would give him a shock and was yellow... not bright white/blue.

He seems to think I should convert the distributor to an electronic first... zip tie the choke and see how it runs. Then look at the carb / thermostat situation. Sound reasonable to you guys?
 
"Yellow spark--and yellow snow

"Yellow spark--and yellow snow--should be avoided!

If he was able to bare hand those wires, you have a really lousy spark! Instead of converting to electronic--which is a good idea--you might do a conventional tune up first. New points and condenser might get the blue spark back. If not, the coil needs to go.

Jeff

PS: You should see at least a 1/2 inch bright BLUE spark while cranking it over."
 
"I read the posts with great i

"I read the posts with great interest. Last weekend I started to experience similar symptoms, had the carb rebuilt, and still no change in problem. One old timer suggested that I pull the valve covers and check to see if all of them are functioning correctly while the engine is running. Will this assist me or waste of my time?}"
 
"Do yourself a favor. Take out

"Do yourself a favor. Take out those breaker point sets and throw them as far as you can, replace them with pertronics or electric ignition.Points went out with button top shoes. Check and set the timing for full advance at 3000 rpm and after that start messing with all the other stuff."
 
"..."One old timer suggest

"..."One old timer suggested that I pull the valve covers and check to see if all of them are functioning correctly while the engine is running. Will this assist me or waste of my time?}"

You'll end up with oil everywhere, that's for sure!

I'd start with the basics: Rev the motor (warmed up) to 1,500 rpms and pull then reinsert one plug wire at a time from the distributor cap. (Use insulted pliers and heavy gloves.) If a cylinder doesn't respond, pull its plug and take a look. If TWO don't respond, try switching these two plug leads--they may have been switched.

Next, put a timing light on it, then rev the motor to 3 grand and see if the mark moves dramatically. If not, the advance mechanism might be rusted.

Jeff"
 
"Thank you Jeff for the advice

"Thank you Jeff for the advice. I will do steps ASAP. I returned the rebuilt & requested they double their work.

The shop also suggested I swap the known good engine carb onto stbd engine, to check if engine is without fault.

Also, they suggested testing the rebuilt on the good engine.

I will revert with results soonest.

Bobby"
 
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