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View Full Version : Still cursed.. BBC 454 loads up while planing-POOF



EstorilM
05-21-2012, 12:28 AM
I just can't have an enjoyable weekend with this boat. After countless trips to the shop while working with the install (3hr trip) I really want to see some return on investment and watch this boat run. Anyways, when I picked up the boat from this shop (they had just replaced the intake manifold gasket earlier Friday since it had a nasty vacuum leak during my LAST failed boating weekend) - they also swapped the 23p prop for a 27p prop (these were all that I had to work with, and the 23 was kinda a joke) - I was excited to see what the engine actually had for power, since I couldn't put any load on it with the 23, it would just tach out. For reference, boat is a 24' Black Widow with new 454 bored to 468, 10:1 pistons, roller rocker, all forged internals.. apparently 490hp on dyno.

Took a girl friend out this weekend, picked her up, loaded up supplies.. we were running really late and didn't get onto the water till 10:45 PM :boggled: So I'm pulling out of the neighborhood marina and pass the no wake buoys - I slowly get on it, trim down, planes down.. builds up speed to about 10-12mph and I feel some resistance in the way it's loading up, I push the throttle a little harder and can feel the engine kinda building "pressure", lowering rpm slightly, then POOF/cough and I'm sitting there at 11pm with this girl in the middle of the lake with a dead engine. :nilly:

I pop the hatch... and everything looks normal? Oil is okay.. I turn the key just for the hell of it, and it fires right up?! I try to plane again and same deal.. no go.

At this point I idle it over to the cove which gives me a new found respect for how FAR things seem when you're going ~7mph.


I think a few things are going wrong here, but they've told me they "will make it right this week before Memorial Day weekend or give me a refund on the engine" - I don't want them chasing their tails long with this one, since a) I hate people just screwing around in my boat to begin with, and b) I'm tired of 3 hour trips and wasted weekends only to discover new issues.

Previously I had 21p and 23p props on the boat and I don't think either of them loaded the engine up enough to see if there were any high-HP type issues with it like fuel or air delivery. They removed the bypass system on the fuel pump (how it was when I got the boat with a dead 454) and connected it directly to the carb on new engine (Sea Demon 830) - the block on the pump clearly has return AN fittings on it for the return type system, but I'm not sure if it needs that. When I came in the next day I let the engine do the same thing when I pushed it, but with the hatch open so I could look at the glass float bowl indicator.. it didn't LOOK like it had run out of fuel, but that pump might be filling up the bowl instantly after the engine cuts out so it's hard to know.

I think this problem always existed since my engine install a few weeks ago, but I was still breaking it in and didn't want to put the big prop on it yet. Even if that prop is slightly too large, the engine obviously shouldn't just shut off.. so I don't want to focus on that (besides, personally I think a 500hp engine can spin a 27p prop - I'm just far from convinced in the power of this engine yet).

My throttle travel also seems limited, I need to check the rigging but the throttle lever hits a stop at around the neutral position of the shifter lever - I know that's wrong, but I also think the carb arm isn't moving all the way from what I saw / felt with the 23p prop - carb arm is 1/8" from stop location still.


My main question is simply... what could they have done when they replaced the intake manifold gasket which would cause something like this to happen? Or do you think it's totally unrelated and I'm simply discovering a fuel problem since I put the larger prop on there for the first time? Is that how an engine would behave if I drained the float? On the return trip I did manage to "save" it right when it was about to cut out I killed the throttle and after a couple coughs/throttle pumps it returned to idle and ran in the lower throttle positions just fine.

PS before I gave up on my weekend saturday (I was just going to put the 23p back on real quick) and checked with the hatch open.. when I really got it to shut off to check the float indicator, it coughed REALLY loud - probably just because the hatch was open, but when I turned around EVERYTHING back there was covered with water?? :eek: I never did see an actual leak, or damaged hose or anything.. and noticed water draining around the hatch gutter and into the drains - I GUESS because the engine stopped, it just swamped everything back there (the black widow has like zero space behind hatch hinges, maybe 6") but I'm not sure how I got water on the engine, intake manifold, etc.. but unless a water hose was damaged, that should pretty much be impossible right? I mean unless it did just get swamped for a second.

craigdskilling
05-21-2012, 08:11 AM
I had a problem like that one day try to get up and would shut down but my gauges where bouncing around when it would dye.I could nurce it back and to the dock but if i tried to put power to it boom dead.my boat is a18 with 400+hp 383 turns out it was my key ignition was grounding out or was just old.went to local tse store picked up new key and everthing worked great best $10 bucks.just my 2 cents some times it can be the simplest things or not.boating is so much fun lol.good luck craig

EstorilM
05-21-2012, 09:12 AM
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Thanks man, that's a good reminder - I'll keep checking the simple stuff too!

oledawg
05-21-2012, 09:49 AM
I would think that if it is truly just "loading up" then an on the water carb adjustment is in order. I have a double pumper Sea Demon 830 also and am in process of working out of the loading up since installation of my new 482 BBC. Never had it flat stop on me though. I am in the middle of a 20 hour break in regime where I don't exceed 3,400 rpm and if I push the throttle down too quickly it will indeed bog down. Surely your tech has access to a body of water and can do this. The 27P prop shouldn't be an issue and should run out just fine. I have run all sorts of props trying to find the "sweet spot" and a Mirage 27P is not a bad choice for overall stability, etc., but it will hold your RPM's down, which is not a real problem with a BBC since they are exactly high revving engines for extended periods of time ( I know since I have holed two of them ). On my boat anyway the 27P doesn't give the highest speed, but was still plenty fast.

EstorilM
05-21-2012, 10:43 AM
Interesting - sounds like you've got a similar setup to mine, or at least relatively speaking it's closer than anything else people have been working on that I'm seeking advice from (including the guys at the shop!)

This is just odd to me since these engines were apparently run on the dyno, tuned, and ready to go - when they ran it on the floor for the first time all of the intake manifold bolts were LOOSE :eek: - why the hell did they have those loose anyways? Then last weekend after it got warm, I'd have the nasty shrieking vacuum leak noise, hence why they changed that gasket last Friday.

When it was having trouble idling this weekend (after first start, when cold) I'd pump the throttle and when it reved up I heard that stupid vacuum leak noise again for a split second - so even that problem still exists.

I guess I need a fuel pressure gauge, it might not be a carb tuning issue.. she might just be running out of fuel / pressure. :lookaroun:

oledawg
05-21-2012, 11:05 AM
Well there is actually a fuel pressure gauge mounted in the engine compartment of mine but I haven't ever even looked to see what it measures. I do have an electric fuel pump though, on initial startup when it stops clicking I know that the lines are full and I can fire it up. Usually starts promptly then. Once it warms up I ease it on up since we haven't "tuned" the carb yet and it goes to my temporary red line pretty darn quickly. My tech insisted on putting a rev limiter on so that I would break it in properly and we will reset once the 20 hours are done. The last engine that blew over revved when the prop got airborne so likely we will set the limiter a little over 5,000 rpm. You really don't want the amount of metal in a BBC spinning too fast for too long anyway. There are likely plenty of folks on here that would disagree with me, but one of my boat techs also builds street BBC's and he is a real stickler about not running hard too long. With my old engine which had supposedly 490 hp I could get 72 -74 on a good day, which in a 22 foot boat is plenty fast. The new engine has more horses but I will be quite happy to get a nice smooth, safe, true 70 out of it. When I had a labbed 23p on I got my best speed, but it cavitated like crazy if you gave it too much throttle too soon and it was not very stable at WOT. My 4 blade Solis is solid as a rock, like the boat is on a rail.

MOP
05-21-2012, 05:41 PM
First with the key off put the lever to full throttle, then pull the air cleaner and look down the front barrels the plates should be vertical IE full open. If that look Ok then check the float levels, some setups are finicky.

EstorilM
05-21-2012, 06:59 PM
Yup I'm going to have them fix that 110% finally this week - but even if I was at say 75% when it went *poof*, I'm still not sure why THAT event happened. The other week when I was out with the 23p prop I WAS limited by throttle travel and got to 58mph, but I could kinda "force" it (not too hard, I just wanted to see if it was at the throttle stop or if it was a linkage problem) and it did indeed continue to rev higher so yeah, something just needs to be adjusted.

I think with that prop, I wasn't using anywhere near the full output of the motor however, so I never ran into the issue that killed me this weekend.

BUIZILLA
05-21-2012, 07:52 PM
find another shop, before someone or something gets hurt...

oledawg
05-22-2012, 07:33 AM
From my time on this site...LISTEN to what MOP, BUZ, and FIXX say. Lots of expertise/knowledge. Props, props, from what I have read and actually experienced, ya just gotta to get in the ballpark and then try different ones until you hit the one that suits your needs the best. I now have a nice shiny set of three on my bench and one on the boat. :wink:

Pismo
05-22-2012, 08:34 AM
It is not just the prop being too big, something else is wrong.

oledawg
05-22-2012, 09:07 AM
Could definitely be the timing, so as suggested above check that first as it can bog you down in a hurry :bonk:

pipnit
05-22-2012, 09:14 AM
a couple of years ago I changed my ignition and it was manufactured incorrectly. There was a two way plug that you could flip and flop, one direction was for setting the timing, one was for running. I was getting symptoms identical to yours. It would start right up, idle fine, but when I accelerated, she'd fall flat on her face. There was even some markings on this plug to indicate how it should in oriented. Well, it turns out that it was 180 degrees off. I reset the timing, flipped the plug around and all was just fine.

EstorilM
05-22-2012, 09:19 AM
Pismo - EXACTLY! Thanks haha, that's my point - worst case a huge prop should just turn my boat into a pig, but it should NEVER simply kill the engine lol.

oledawg - that would make sense, since I believe they may have screwed up re-timing when they replaced the head gasket the day before!

mrfixxall - I was heading into the marina TO change back to the 23 that day, but the last *poof* was so crazy I just threw the thing back up onto the trailer ;) I'm used to working on v-twins and such, and they'll caugh or whatever and it's impressive but not too scary, but when a 10:1 big block does it.. stand back!

I can tell you from experience the other weekend that the 23 was a joke though, I could peg the throttles and I'd get thrown into my seat as if I was in a car - then it'd just tach-out with no load. With better throttle travel I'd be in the 60s easy with that prop, but I don't think I can use the 490HP with that prop, it came off a friends Checkmate ZT23 with 300hp 350 MAG. :lookaroun:

BUIZILLA - thanks for the insight but.. this guy does have a 1200hp 25' Talon and the nicest boats on the lake, he does know his stuff I think he just dropped the ball on my boat. Like I said, he's going to get it working before this weekend or he's giving me a hefty chunk of cash back, so I'm convinced it'll be right.

APPARENTLY I just now learned that they tried to mark the timing when they replaced the intake manifold gasket and DIDN'T start it because I didn't give them the key (granted it takes 20 seconds to hot wire a boat lol) but that might explain a lot..

BUIZILLA
05-22-2012, 10:15 AM
either the front float is set too low, or the rear float is set too high.... i'm going first in this direction, since you stated it starts right back up when the hull is flat and level

check fuel pump pressure for 5-7 at idle

EstorilM
05-23-2012, 04:01 PM
Hmm, timing was 9 degrees off.. :boggled: So much for marking it - even if it's not exact it would have been closer than that!!

We will see how she runs this weekend, wish me luck though.