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454 Stbd engine firing waaaay off. Why?

S

SeaJay1987

New member
Here is a little history. 1987 Tollycraft with 454s. New boat owner and first thing I noticed in sea trials was the stbd engine does not give a whole lot of power. No more than 1700 RPMs. She also gives off a fuel sheen and you can smell the unburnt fuel from the exhaust. I have had 3 separate mechanics all say the same thing. They just can't find what is wrong. She runs but has a little vibration. All signs point to firing order and timing to me. Found the firing order of 1-2-7-5-6-3-4-8. Easy enough. But that is not what the engine has configured. Currently she has a firing order of 1-4-6-3-2-7-5-8. I tried to put it to the other firing order but she will not start. Even with starting fluid.
I have had 2 of the mechanics check timing. Replaced plugs and wires. All with no change.
So is my problem a crank shaft? Distributor installed in a wrong direction? Or just straight up over haul her?The previous owners stated it has always been like that (for 24 years). Any and all help is appreciated. Thanks!
 
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Unless somebody has been into the engine and customized it, I suspect your convention/reference may be off....I can't see how that firing order would work.

Are using the GM reference points?

Also, what did "mechanics check timing" entail? the engine won't make any power if the timing does not advance correctly.
 
That engine has not been rebuilt. Or over hauled. She has 1000 hours. So I am sure it is time. So no one has been in it.
The timing entailed a timing light. It made the vibrations reduce but no different in the power.
We were using the numbers from the manual I have.

When she she is in neutral she is able to go past the 1700 RPMs. It is when the transmission is set forward she doesn't go past 1700 RPMs.
 
ok...so the timing was only checked at idle?

which set of timing marks were used?

This is the RH (right hand) rotation engine, correct? if in doubt, check the serial number plate.
 
Good info would be the compression in each cylinder, if the timing advances with rpm to 30 degrees or so, are all sparkplugs firing (check each ignition wire with an induction timing light). Sounds like possibly one or more dead cylinders. Sometimes rusted springs on the old style distributor which precludes timing advancing. Unless badly abused, 1000 hours is about a 454s half life.
 
The timing was checked at idle and at 3000 RPMs. The timing marks are still clearly marked on the engine. We verified that #1 cylinder was aligned prior to timing.
Compression check was done. All cylinders are +\- 5 psi of each other.
All spark plugs were verified firing and sparks. Spark plugs were even replaced to "just make sure" there was enough spark happening.
Verified rotation of the engine. It is the opposite direction. (Once thought we had 2 of the same rotation, not the case)
Everything has been text book. Several eyes have looked all are dumb founded.
 
Raw fuel in the water means cylinders are not firing when they should be.

That firing order business sounds off to me. Since that is a reverse rotator, the firing order is 1 2 7 5 6 3 4 8 PERIOD! Anything else is wrong.

1. Correct that.

2. Get the thing running and start pulling wires from the cap (use insulated pliers and gloves).

3. Note which cylinders react (slow and pick up as the wires are put back)

4. Note which ones don't run and find out why.

Jeff

PS: Don't know what you're using for "mechanics" but this is not a mind boggler.

PSS: Which cylinder are you designating # 1? It should be on the left front (opposite the distributor). Strongly suggest you follow and LABEL each wire at the plug end to eliminate confusion.
 
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#1 is the front left. Wires have been labeled at both ends. We have tried it with the correct firing order. She will not start. i have tried Marine mechanics and even tried a Car mechanic. (Which he only recommended was to swap carbs with the other engine and see what it results. ) Haven't had the time for that one as I need to get some seals.
 
24 years of 1700rpm at wot? :confused:

Do both STB and Port rotors turn the same direction during cranking? If they Don't, that raises the possibility of a chain drive reverse rotation engine. The more typical RH engine is gear drive cam, and the rotor will turn the same direction as its LH cousin, chain drive cam.
 
I think you need to determine if it is an electrical issue or a fuel issue.

Is this a Cruader 454 stbd engine? If so I believe it may be a reverse rotation engine, and if so the firing order should be 1-2-7-5-6-3-4-8. The distributor will rotate the same as a conventional engine. When it is running is the belt rotating in opposite direction than the other engine? Next you may have to determine when the #1 cylinder is at TDC on compression stroke and that the rotor is aimed at #1 plug. If not, correct.

A fuel problem could be a partially clogged anti-siphon valve, water in gas, bad (old) gas that has phase separated, clogged vent on tank, collapsing fuel line, clogged filter on carb, and a number of other causes. Do you see fuel get sprayed into the throat of card when you pump the throttle? If not it could be a bad fuel pump. There are many ways to isolate the problem and one that eliminates a lot of what I said above regarding fuel is to connect a portable tank directly to the carb. This eliminates the fuel quality, tank vent, anti-siphon valve, and supply hose from carb to tank. If one of the so-called mechanics recommended swapping the carb, he must think it is a fuel issue.

It seems pretty weird that the PO said it has always been this way. ReallY ???
 
Had the same issue on one of mine. After all the obvious, checked the advance mechanism. Both springs rust d through. Good at idle and when not in gear no more than 15-1800 rpm. It's a quick check to look if all else seems good
good luck
j
 
First, since the engine runs but is rpm limited I agree that it is most likely a fuel flow issue or lack of advance.

Second, the firing order you observed is impossible so you are not counting correctly from #1.

There are four throws 90 degrees apart in the crank shaft, each with two rods. Since the even and odd cylinders are 90 degrees apart the pistons on each throw will reach top dead center 90 degrees apart. In other words, #2 always follows #1 by 90 degrees (or the reverse #2 following #1 on a normal rotation engine) since they are on the same throw. Likewise, #4 TDC always follows #3 by 90 degrees, etc. Since there are four throws and 8 pistons, TDC will always be reached by a pair of pistons at the same time. The pairs that reach TDC at the same time are 1-6,2-3,4-7,and 5-8. The crankshaft design determines these pairs and cannot be changed. The complete engine cycle is 720 degrees (2 rotations) so only half of the TDCs are on the firing stroke. The engine designer can choose though camshaft design the firing order he wants, as long as he picks in order from these pairs. So your engine designer chose 1-2-7-5-6-3-4-8 (or the reverse of this order for the other rotation). These choices are fixed by the camshaft design and cannot be changed. He could have chosen to follow #1 by either #2 or #3, but nothing else (in the other rotation he could follow #1 by #5 or #8 but nothing else and work though the list the other way). But your observed order (#1 followed by #4) does not follow these rules and therefore is incorrect. And it is so incorrect that the engine would not run so your observation must be wrong.

So I would recommend you focus on fuel and spark advance and leave your firing order concerns alone.

Good Luck!
 
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