more gas engine trouble.

[67hat34c]

In prior posts i have discussed recent trouble with one of our crusader model 350's. we had the carb rebuilt, i pulled intake and installed new lifters, got all adjusted well and ran her. ran fine except it would not turn more than 3700, did not race up and die or sputter or anything else, just would not go any faster. port motor ran up to 4000 and ran fine. guess starboard motor not turning up caused port to hold at 4000 instead of 4400.

got to boat friday night and went through starboard motor again, cked throttle linkage and it was wot. checked running volts to coil and it was 13.00 checked timing and it was fine, looked to see if advancing and it was fine. pulled the plugs and noted all black except #5 it was clean, not even burnt. now these plugs only have a couple of hours on them, changed when i did the carb and lifters. someone on the dock suggested it was a bad spark plug and we had dead cylinder. oh also i rechecked all compression and all were between 162 and 165lbs, same as they were in may when ckecked last time. anyhow i decided to go fishing next day and run on 15cyl as we have apparently been doing this for a while now. well we hit the inlet and gave it the juice and the thing backed fired and sputtered etc. backed off and turned around and headed back. gave wheel to dad and went down and pulled deck open, saw spark coil wire off with flame /arc so i shut it down to re attach and found it soaked with oil, blown coil. went back to the dock and changed the coil and also tested the a few cyl by pulling off the plug wire, #1 slowed it down, #3 slowed it down, #5 nothing. changed that plug and it made no difference. ok bad wire. (msd 8mm wires changed about 3 yrs ago) well we fished, got 4 barracuda and one dolphin and came back. pulled wire and took it home. Put wire on ohm meter and it seems fine.

WTF is going on ? is wire breaking down at higher temp? possible not attached to plug properly as it is hard to get to behind the oil dip stick tube?
the wire lights up the timing light before the spark plug boot. of course that does not mean there is enough juice to light the plug i guess.

Going to get a couple of new wires and check it again possibly friday.

side issue, amazing how much stuff you find wrong when something quits working properly. none of it related but all needed attention. lucky that there is not a major mechanical issue. very happy with compression although dont know why so high, by the way have run a couple of cans of sea foam through it since may when this all first came to a head. thought that would have cleaned up cyl and lowered compression a little.

by the way the first compression stroke on each cyl shot the compression way up very fast, the rest of the strokes got it the rest of the way a little at the time. i take it that this is good.

 

[Boss Lady]

The easiest way to check for a bad wire is to move it to another position and see if the juice is firing the other plug.

I had a bad lot of spark plugs once. The ceramic was broken at the base and when you held it up to take a look it was fine and we did an out of engine spark test and that was fine, but when you turned the plug down to insert it in the engine the ceramic would slide down and block the gap and would not fire. Replaced it with another new one and it had the same symptoms. It took us a while to figure it out. but I had a whole box that were bad.

Rule #1: replace with known good when tracking down a problem. Just because it is new doesn't mean it is any good.

 

[sammidog]

If they are champion plugs replace them with AC. Ever since I was 16 I always used Champion plugs but ran into bad plugs more often than I thought I should. I switched to AC and have had no problems ever. I know some people swear by Champion but I don't use them any more. Just my humble opinion. Also good post before mine; switch wires, it could be a bad wire. Check the cap also, corrosion on that terminal?

 

[Maynard Rupp]

I don't agree with Sammidog. Champion plugs are just fine. Take the plug out, pull all the plug wires and arrange them so that none are going to ground. Now clip #5 wire on its plug. Next ground the plug to bare metal on the engine. Probably best to wear a glove so you don't get zapped. Now get someone to crank the engine. You should see a spark. If you don't try another plug. Still no spark, try any other wire in that cap socket. Still no spark, I will bet you have a bad distributer cap. A small crack here will allow the spark to go to ground. You could switch caps with the opposite engine. I will bet the problem will travel with the cap. Cheap fix. The compression results you are finding are very normal. First rotation gives about 90% of final result. Remember, these are not rocket motors. Everything is logical.

 

[67hat34c]

plugs are ngk.

i changed #5 plug and nothing happened, did not try to dry fire it although.

either way i will get a new wire and a cap and go back and mess with it.

by the way caps mabe have 75 to 100 hrs on them. replaced them last year with oem Mallory caps and rotors.

 

[sammidog]

Do they have brass terminals? I had a Crusader 350 fresh from the factory with something else (aluminum?) and after one season they were a mess. I made sure the replacement was brass and never changed it in 8 years. I know that is not your problem given only one bad cyl. but just some FYI.

 

[Maynard Rupp]

The PO of our 36 Hat had Prestolite distributers installed. They do solve some problems. if your #5 cylinder is not firing and the wires are on the correct plugs, you must have either a bad wire or a cracked cap. Simple stupid logic can't be wrong.

 

[MikeP]

Backfiring relating to ignition is usually a symptom of miswiring or wires cross-firing. Is it backfiring through the carb or in the exhaust? Backfiring though the carb could also be caused by a vacuum leak.

Check your plug wires, and as Maynard suggested, the distributer cap. Cross-firing can occur there as well. An old timey test for cross firing/bad wires is the "night test." After dark, crank up the engine(s) and with NO lights on that can illuminate the engine area - the darker the better - observe the engine running. If wires are misfiring/crossfiring you will see the "light show." Sometimes it can be quite dramatic even though the engine sounds ok. Move the wires around with a stick (NOT a metal rod!) as you observe. Note that MISwiring will not be detected - this will only identify that the wires are arcing thorough the insulation.

Related to this - poor wire looms, either custom or home made are a notorious source of misfiring. Some don't have any grommets and the metal of the loom can, after a very short period of time damage the insulation enough where the wire can short to ground under load but not under less demanding conditions.

Once a wire or dist cap develops a carbon track which it will when it shorts, it CANNOT be fixed. It must be replaced.

Remember - spark plugs/wiring are under very light load at light power applications so a system that looks fine under no load could still be a problem under heavy load. It is NOT possible to put the system under heavy load with the boat (car/whatever) in neutral regardless of the RPM.

How is the gap on the plugs? An excessive gap will fire fine when not under load and fail to fire under load.

All the above addresses misfiring/backfiring but it does not address what I understand to be the main issue - As I understand it, the engine will achieve and hold 3700 RPM. It does not sputter and missfire at that speed, it just won't exceed it. IS that correct? If so, then the only ignition related thing I can think of without actually looking at the engine myself that can cause this is timing and plug wires 5/7 being reversed.

I know you said you checked this but...the timing for a 350CID small block should be in the 6-10 degrees BTDC range. 8 is always a good starting point. What timing do you have set on the engine? Is there a vacuum advance unit on the distributer? (I'd guess "no") If so, the timing must be checked with the vac line disconnected and plugged. The centrifugal advance should have all the advance in by 3000 RPM. Is that the case? Look at the timing mark as you increase the RPM, does the mark move as you increase RPM? It should not move any further after the rpm hits 3000-3300. You probably don't have a timing tape on the damper so you cant actually tell what the full advance is. But it should be between 34-38 degrees.

Other causes - restricted exhaust, insufficient fuel (floats set too low, restricted fuel supply due to partially clogged filter(s). Usually restricted fuel or low float settings will allow the engine to achieve normal or near normal max RPM but, as the carb's float bows empties, the RPM will drop to a lower rpm and then surge within a several hundred RPM range.

I don't know enough about marine mufflers to know their "fail" mode. But I have seen cars that ran perfectly fine but due to collapsed baffles (internally) they would not exceed 3000 RPM under load. I've also seen them so bad that the car wouldn't do anything but idle! Whether this can happen with a marine muffler, I don't know.

Extremely poor valve settings could also cause the lack of top end power problem but since they are hydraulics, it's hard to imagine they could be that bad. Once zero lash is set, it's all "automatic."

I don't care for this shotgun approach to a problem but troubleshooting by long distance is difficult. Fortunately, as Maynard said, none of this is rocket science. (Frankly, I'm not sure Rocket Science is rocket science) Usually it turns out to be something where you slap yourself and say, "How did I miss THAT?"

Good Luck!!

 

[67hat34c]

mike these are 454's, model 350. Timing is at 10 degrees at 500rpms.

back fire was caused by the output wire on the coil that blew off (leaked oil), it sent a shower of sparks all over the place, once coil was replace and wire hooked up the boat ran fine all day with exception of dead cylinder #5. ( because we worked on it friday night and i saw that coil wire was on , it must have blown when i gave it the juice. )

yes the mechanical Mallory Distributors are advancing, did ck that. I re cked timing and also plug wires v firing order, even numbered them on the cap.

Compression is also good, cked all in may and again last week 162 to 165lbs

Plug wires are MSD 8mm, I cut and assembled them about 3-4 yrs ago, they did work perfectly at one time as we did get WOT then. Seems like just the one wire is bad as far as i can tell., did both engines at the same time.

I plan to fish again on 11/03 so may take that friday off and mess with it some more, replace cap and the wire.

 

[Jackman]

10degrees at 500rpms? I thought my Crusader manual said 10degrees at 650-700rpms.

 

[67hat34c]

Jackman, we have 2 manuels, one is shop manual other is user manuel and there are multi conflicting notes in each, shop manuel says 500 rpms. however, rpms dont matter as long as it is slow enought to prevent timing advance. mabe next time i am there i will start at 500 and increase speed to see where it starts to advance

Heck one manual says change oil every 100 hrs, other says 50 hrs, one says normal idol is 650 in gear the other says 750 in gear. Both manuals were with the boat when we got it and apparently were provided with the engine installation in december 88.

 

[MikeP]

Sorry, I was thinking 350 as 350CID... If the book calls for 10 degrees, then 10 it is!

I have to admit I would suggest that 10 is too high for a chevy big block. They usually want around 34-35 degrees of total advance and since most advance units add around 30 degrees, this would end up at 40 which is too high. HOWEVER, my experience is with "land" engines and since marine engines are "detuned" compared to street engines, the advance can be higher. In any case, a few degrees of advance beyond optimum will not affect the engine in the way you are describing anyway.

As far as setting timing, the best way to set timing at idle is to reduce the idle to as slow as it will run, then adjust the timing. This will ensure that there is NO advance being applied by the mechanism at that speed. After setting, increase the idle to the optimum level. I would set idle at whatever works best for the boat, allowing you to maneuver at idle as you prefer, rather than setting the idle to some specified rpm.

Actually the best way to set timing is to totally ignore it at idle and set it at 3000 RPM. You need a timing tape for that. You set it so that at 3000RPM you have the specified total timing. Then you don't care what the idle timing is but you can check what it reads and then set timing at idle to THAT figure from then on.

If you are really into it, you can advance your max timing by 2 degrees at a time and make a WOT run each time to see how the engines act. Basically what you are looking for is the max timing that can be used BEFORE "pinging" occurs. Once pinging occurs - and back off the throttle when it does - reduce the timing to the point that it does not. Note that differences in fuel will affect this. Naturally it's "safer" to set the timing conservatively to account for different quality fuel that you will encounter.

On performance or competition engine builds we always set the timing with the engine using the specific fuel the owner would be using in that vehicle. This is probably not practical in a cruising boat since the fuel brands are variable from fuel dock to fuel dock. And the slight performance advantage that this provides is of no practical value in the water.

I'm really intrigued with this problem you are having with the engine not exceeding 3700 RPM. By your description of everything you have checked, I'd say it can't be happening!

But since it is, we are obviously missing something very basic.

 

[67hat34c]

Mike, only thing is the dead cylinder, pulling the plug wire on and off makes no difference on the #5 so i would guess that is why it is running out of power. also the flo-scan showing about 3-4gph more on that motor than on the port engine. could be some air bubbles but also could be dumping more through the carb and not burning it.

all plugs were new a couple of weeks ago, ran the boat out in min wake zones a couple of times and ran up to 3200 a couple of times but never pushed beyond that. anyhow when i pulled the plugs they all had a film of dry black carbon except for the #5 and it was clean, meaning no burning at all. did not take camera otherwise would have photos. anyhow that is when i re checked the compression an verified it was good. I found timing was at 12 so backed it to 10. have hard time making it right when i tighten the bolt.

 

[krush]

If you have an electronic timing gun or even one with a knob (not as accurate) you can set max advance without using timing tape. Just advance the gun to what you want and while out crusiing turn the distributor.

Useless trivia.

 

[rockdoc]

Hey, I just went through an identical problem with my 34' 64 sportfish-had non stop problems, finally it was the distributor cap! It made spark on cursory exam,, but was ultimately the weak link. Swapped it out and now my 454's make the thing run like a striped-assed ape! I'd previously replaced everything, but it went bad in a month. The parts are so cheap for ignition-its reasonable to replace just about everything rather than having a mechanic look at it!

 

[MikeP]

Electrics and salt water are a known terrible combination. The high voltages present in the ignition secondary circuit are an even bigger problem than "normal" voltages and the parts have to be monitored/maintained very carefully to avoid unpleasant surprises. Of course a lot depends on the particular set up as to how much salt spray/mist gets into the engine area.

I had a gas-powered boat in Alaska that had constant problems. The dist caps and coil towers would carbon track in a month if they weren't cleaned at least weekly. We got in the habit of popping the dist cap after every outing and spraying/wiping it (in and out) with WD 40. Did the same with the coil tower. After that, we had no more trouble with carbon tracking between normal tuneups.

Oh well, at least the coils and associated parts on the engines we are dealing with on this site are not made by Lucas!

Lucas work ethic: "A good days work and home before dark!"

 

[david_lavigne2540]

Ok, lots of people mention WD40. But it has water in it and we are trying to avoid water aren't we?

Of course, we are doing a salt flush on this, so it may be a good thing. Opinions?

 

[MikeP]

WD 40 is a water displacer; it does not contain water. Spray it on a damp surface and watch the water "run away!" It was originally developed to get rid of water and prevent corrosion on electrical circuits so this is precisely the application for which it was designed.

But I always wondered, what ever happened to WDs 1 through 39?

 

[67hat34c]

yes it was developed for the military in WWII WD means Water Displacement, believe 40 is either the year or the formula number.


my problem persists however. we have one cylinder giving problem

strong compression, 162 to 165 all cyl.

plugs ruled out.

wire ruled out ( i think) put a spark plug in and it fires, however due to weather we did not take it out and heat it up. changed #5 on starboard motor with one on the port motor and will run it this week.

only thing left is there is not enough fuel air getting into cylinder with each stroke. possible cam lobe? the lifters are new, did not note any unusual wear on old ones, just replaced because one of them was ticking. I plan on checking the lash on more time and then plan to measure the valve travel and compare with other cyl on same side.

If i have to pull the cam then it wont be that bad, have plenty of room in front of the engine approx 3.5 to 4'. (try to do this in a searay)

 

[MikeP]

Cams just don't wear under normal circumstances But then again, it's not IMPOSSIBLE and I suppose stranger things have happened.

Valve adjustment? Possible but if the lash is too tight, you would show no or very little compression; if too loose, you'd normally hear it clattering. But pull the valve cover and watch the rockers/valves as the engine is cranked. If that cylinder has a valve that isn't opening or otherwise not functioning properly, it will be apparent in comparison with the movement of the valves/rockers on the other cylinders.

If one cylinder isn't firing the obvious suspect is an ignition problem - bad wire (very high resistance or arcing to ground/another wire), bad plug, bad dist cap. I know you said you checked all this but...