Need Engine Advice from the Mechanically Inclined

[NautiqueJared]

I am still dealing with a serious issue that began after a crushing defeat of 'My boat vs. a tree stump'. I have a '92 Barefoot with the 454 and currently it has less power than my friends '94 Geo Metro. Whenever I put the engine under load (accelerate) it bogs down and backfires through the carb. It has been doing this since last year after the hull of the boat was fixed and I tried to take it out again. I haven't put it in water yet this year but when I pulled it out of storage and cleaned it up a couple weeks ago, I started it and it was still severely lacking in power. I took it to my mechanic and he thinks he has eliminated the fuel line, the carb, the fuel pump and he's checked compression as well. I took the advice of a few fellow PN members to switch the coil pack to a distributor and although it was probably a good move, it didn't fix the problem. I am thinking that it was either not timed correctly after the distributor install or the timing gear (which I was told is nylon) may have been damaged in the wreck and is causing the timing to slip and throw it off. I had it fixed last Sept./Oct. and only tried to run it on the lake once afterwards with no luck. Please let me know if y'all have any advice / path forward. I would be greatly appreciated it as I am definitely ready to get this thing running again since it has lacked the nuts to pull anyone out of the water from May '09 - present. I am also currently trying to figure out who to take it to in the Houston or Austin area that would know how to cure my ailing so I can put this to rest.....a whole year wasted was definitely salt in the wound.

[WakeSlayer]

Have you yourself tried timing it? It is extremely easy to do.

[NautiqueJared]

No I haven't....I've seen it done and it seems easy but don't have a light or the specs on hand.....not sure what the adv./retard should be with the distributor installed.

[WakeSlayer]

I would try and borrow a light from a friend if you can. It is especially easy if you use an adjustable one. Clip to the battery, positive first, clip the sensor on plug wire #1, in your V-drive BB, it should be the port(passenger side), farthest to the rear (someone correct me if this is incorrect) Make sure all the wires are clear of the pulleys, etc. Start the engine, and point it at the crank balancer. There will be a mark on it, and a pointer of some sort on the block just above that. Your base motor timing should be set at abtou 10* BTDC. If it is off, and I think it is, shut the motor off. Loosen the bolt that hold the disty down, enough that you can move the distributor a bit. Start the motor, adjust the distributor to where the line matches up with the timing mark on the block. Shut down, tighten the bolt, remove the light, then test drive.


Edit: lights are cheap, like $30-50 for a basic one. That and a laser temp gun are two very cheap, very handy tools to have.

[core-rider]

Check the timing like WakeSlayer says, but also check the firing order (are the plug wires going to the correct cylinder) and it would be good to check the plugs as well to make sure none are fouled out or damaged. You may want to check the cap and rotor as well to make sure nothing is damaged. It definitely sounds as if there is a spark issue.

Also, since it has been backfiring through the carb you will most definitely need a power valve for it if it is a Holley carb. This will affect your acceleration off idle causing a stumble until it is replaced.

Here is the PCM manual for 1991 engines. http://www.planetnautique.com/Correc...s/1991/PCM.pdf
You will find the firing order, timing specs, plug gap, etc there. The 1993 manual has the same info on page 16 but for some reason there is no 1992 manual listed. I think you will be safe though. It looks as if they offered 2 different 454 engine models back then so pay attention to the first few pages of the manual to figure out which engine you have cause the timing is a bit different.

[Rick]

Reverse Rotation?

I think this engine may be reverse rotation If someone put the plug wires in the regular rotation order you would get the symptoms you describe. Check the firing order and make sure its correct. Also timing will be backwards also so there is a good chance the timing is waaaaay off if the plug order is correct.

[Nautiquehunter]

Let me get it straight . The engine ran fine untill the stump was hit . What all was done since then?

[74green]

Autozone has tools you can rent for free. Ive gotten a timing light to use from there before.

Although not a boat...on older chevy trucks I have seen bad compression, incorrect timing adjustments with the distributor, and improper valve adjustments that all would cause either or both back firing up the carb and bogging down...exactly like your problem.

Id start with the firing order like mentioned by the other PN members and be certain that is correct and no wires are going to the wrong cylinders. Then check the timing adjustment as wakeslayer mentioned. If that doesn’t do the trick you may need to look into adjusting the valves on the heads. Also as you mentioned the timing chain being improperly adjusted/aligned could possibly be something to look at.

[Mikeski]

Assuming no major tune up was done that would allow a major change in timing or miswired sparkplugs, I would focus on the carb. Backfiring through the carb is caused by a lean condition. If it has sat for a while one or more of the carb's throttle body passages or valves could have become clogged creating a lean condition causing the backfiring. Is it running hot?

[NautiqueJared]

NautiqueHunter: For reference, and hopefully without rambling, here is the order of events last year. On the first outing last year I left my homemade flush kit valve open and overheated my engine. I changed out impellor, spark plugs and fluids and the boat was running great. I went up to Granbury Lake, put a brand new prop on and an hour and a half later had a new anchor. Prior to the hitting the stump, that was possibly the best that boat has run since I purchased it in September of 2007. The stump, that was hidden under the surface, sheered off my rudder, destroyed my new prop and ripped the shaft bracket out of the bottom of the boat. Two sack pumps and a bilge later I kept it from sinking (big mistake in mind now) and I took it back home to my mechanic. He assessed all the damage to be structural ($5k) and he proceeded to fix the bottom of the boat. Immediately after getting it out of the shop I began to have the problem of the boat bogging down. At first it was intermittent and I occasionally would be able to pull riders but then it began bogging all the time. I took it back to my mechanic and he took the carb apart and visually inspected it, he hooked up a new fuel pump, he checked the compression, he hooked up a new gas tank to eliminate bad fuel or lack of, he checked plugs and firing order of wires. I then had the distributor installed to replace the coil pack and that did nothing to remedy the problem. Oh, I also had my alternator tested back when I still had the coil pack and that came back ok.

Mikeski: No the engine is not running hot when I run it at idle on a hose.

Thanks for all of the suggestions so far. I will start off with the easiest fixes (i.e.- firing order and timing) and move towards the more complicated problems (i.e. - timing gear and rebuilt carb). If anyone else gets any good ideas, let me know.....other than running it into the dam.....oh wait, might not be possible since I can only get it up to about 9 mph....anyone want to surf? I'll keep everyone posted on progress (hopefully).

[jasper]

You said it bogs down under load. Can you get the rpm up without any load on the engine?, i.e. take the engine out of gear and gas it to run up the rpm. When you do this, does the engine seem to run normal out of gear?

[bobchris]

Why haven't you look at the timing closer? why haven't you replaced the power valve?

It ran great now it doesn't, why are you dicking with the firing order? did it change by it's self because you hit something? no, Did the fuel pump all of the sudden go out? no, why are you looking for stuff to magicly change by it's self? like chasing your tail maybe?



You locked up the engine for a breaf moment when you hit the log, so you should be replacing the power valve in the carb, unless it's FI, most likely source of the backfire, next you have to look at the timing relative to the valve train to see that the timing chain didn't jump a tooth, which most likely it did or stretched at the very least.

So find a better mechanic and quit waisting your money on him chasing his tail, because the only things effected by riping off the prop and rudder are internal to the transmission and internal to the engine, rechecking the firing is just stupid and a waiste of time so is the fuel pump pressure and a new distributor, don't care what you think the timing is set at untill you pull the valve cover and look at the actual timing events that need to happen your just pissing in the wind and retiming it so that the spark plug fires at this time or time doesn't mean a **** thing if the valves are not opening and closing when they have to be and the only thing controlling that is the timing chain and gears.

So pull the motor replace the timing chain and gears and be done with it. not rocket science simple logic actually if you know your way around a motor.

[2gofaster]

Either your guy doesn't know the ins and outs of a carb like he thinks, or it's jumped timing. Is it backfiring through the carburetor or out the exhaust? Hitting a stump hard enough to do all that damage is quite the shock to the engine. I have no idea if it's possible to get the front cover off with the engine in the boat. I suspect that it's not, unfortunately, which means the engine needs to come out. But Bobcrhis is right, you need to be able to put a degree wheel and piston stop in it to find true TDC and then work from there.

If it's backfired once through the carb, then the power valve is toast and needs to be replaced, whether there are other issues or not. Backfiring, though, will always be either caused by the carb, or timing, or both.

Dockside Marine, in Conroe, is fully qualified to look it over and troubleshoot it. But on that boat, just about any place SHOULD be able to troubleshoot that.

[bkhallpass]

Hey guys, I'm not a mechanic. However, I noticed that the boat is a 92. 92 BFN was a V-Drive, Correct?

If so, with the damage he had, I would guess they removed the engine when doing the repairs. Only suggesting this because I don't know what has to be loosened, tightened, removed or changed when removing the engine from a VDrive BFN. Just thinking something might have been changed which would not be the case in a direct drive where the engine would likely be left in place to complete the hull and running gear repairs. I don't know. Maybe the distributor had to be removed to get clearance to get it out of there, and whoever put it back didn't realize it was reverse rotation. Maybe not. I'm not even positive the 454 Vdrive was a reverse rotation. Again, not a mechanic.

BKH

[Nautiquehunter]

Good suggestions with the power valve and timing chain. If it did jump the timing chain you should see your compression readings erratic high and low. The best way to check valve timing is to use a degree wheel and watch the operation of the rockers . Is it now running on a distributor or coil pack? Also make sure the vibration damper has not turned it is rubber sleeved I have seen them turn this will cause timing to be set incorrectly.