454 initial timing questons
 

Hey gang, I know from researching that base timing for a 454 should be somewhere around 8-10 degrees and the thunderbolt module adds another 24 to get to a total timing number of 32-34. My question to the experts out there is what would happen if initial timing was only set to zero? I think a ****up was made by my mechanic. initially boat was idling great and sounded good. This was a fresh rebuild, we broke in cam at 2000-2500 rpm on the trailer backed down the ramp but discovered water coming in somewhere so we didn't run it that day. They took drive off and double checked bellows and couldn't find anything, They tried a couple fixes for that and finally we decided to say screw it and try to run the boat. So we started out and the motor seemed to be running good but after about 20 minutes we got a temp alarm and then the boat wouldn't idle properly. Very high idle. We did get the motor to cool down enough to idle back to the dock but the idle stayed really high. They did some tinkering and kinda sorta maybe found a vaccumn leak when they sprayed some carb cleaner around some different areas though it didn't seem real distinct. Also important to note that when the temp alarm went off and we shut it down it was dieseling big time. The following day at the shop we started it up and again it was idling high right out of the gate and dieseling upon shutdown. Today, my mechanic informed me that the tech that worked on the boat and set the initial timing said he set it to zero which my mechanic knew was incorrect and part of the problem. I like my mechanic, but he's a younger guy and I don't think he is as knowledgeable with old school carburated stuff. The tech he had working on it is a nice enough guy but this isn't the first thing hes ****ed up. After this failed attempt we found more water in the bilge and finally were able to pinpoint it to the recently replaced steering pin. They installed a new gimple ring using the jr marine method. They took it apart this week and discovered the seal between the bushings was missing. This tech did that work too. So again, I like my mechanic, he has apologized and made it clear to me that the steering pin correction is on his dime and he is doing everything to make this right. He has worked dilligently on this boat but without a doubt hes struggling to hire good experienced talent and hes trying his best to oversee, run ashop and not totally babysit everyone. my concern now is that we messed something up running it as much as we did with the timing out of wack. I'm hoping maybe just soemthing with the carb but i suspect simply getting the timing set properly isn't going to resolve this issue because it was running okay and then suddenly now it's not. Would the dieseling and backfiring have done something to damage the carb? BTW, carb was freshly rebuilt as part of the engine rebuild process and worked fine on the motor the brief time it was used before motor blew up.

Sorry, thats all a mouthful. I'm starting to lose my patience and just want to get this damn thing figured out and on the water.

Engine may have overheated due to timing being slow, or maybe something else going on. Not sure 10 deg slow would make it overheat that quick, depends on how hard you were running it. If you have a Holley carb the power valve is probably ruptured from the “dieseling “
That will make it run rich though not lean. Hope it didn’t get hot enough to damage anything.

We had opened her up a good bit and briefly were up at 5k rpm so we weren't holding back.too much. We were able to get her cooled down pretty quickly and while idling back to the dock she stayed plenty cool.
It is a Weber carb, not a Holley if that makes a difference.

Hard to believe it idled well and ran up to 5000rpms with the timing 10* retarded.

I am a novice with this stuff but if I hadn't seen it and heard it with my own eyes I'd be questioning it. Iv never run this boat before ; I bought it as a fun project to possibly flip or maybe use for a year or 2 then sell. Scored it cheap from a friend that owned it for close to 20 years and had it sitting with a blown engine. Reason I give you this back story is just to say that I couldn't really speak to the performance numbers I was seeing because I didn't have a benchmark from previous use.

I'm just deathly scared that something like a cam lobe got flattened and we will have to pull motor again.

Would be pretty low on power, and wouldn't want to start easily being 10 deg retarded. Also, dieseling is normally caused by a "hot spot" in the engine burning the fuel or highly advanced timing, not retarded. It shouldn't have caused any long term issues but not sure what you have going on.

I’d have that mechanic check to make sure that distributor is in proper and it is set pointing toward number 1 cylinder at TDC before he goes checking the timing.

Let’s see some pics of this schit show. Frt of engine 1st.

Many variations of ‘rebuilt’ engine. Give us a parts and machine work rundown.

Do a compression test.

Bored 30 over. 18cc icon forged dome pistons, comp cams Xtreme marine 262h cam kit, peanut port heads. Bought motor used last year, when we sorted through all the. It's and got it running, it blew up first trip out. Tear down by revuilder found evidence of serious water in one of the cylinders the amount of rust was why it had to be bored 30 over. Looks like the rust are up the rings and made it lose compression on that hole. Machine work was done here in Tampa by united speed world, a well regarded shop that's been around quite awhile. Motor rebuilt by local engine rebuild shop also with good reputation and plenty of experience with marine engines. Since it's a gen 5 flat tappet motor I made the decision to do the mild cam upgrade and forged domes to boost power. New manifolds and risers were put on our of an abundance of caution inspite of the ones that came off looking like they were in good shape.
link to cam https://www.summitracing.com/parts/cca-k11-232-3

This should be my 10th post hopefully I can post pics now but pretty basic gen v 454 . Do I dare tell you guys that it's in a sea ray sundancer, not a go fast boat lol

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It had no problem starting and was idling pretty damn smooth to me but again, I'm a novice with this stuff. I am worried something happened to the cam, I know you are supposed to start it up and get her to 2000-2500 immediately for 20 minutes. They didn't do that right away, it was started and stopped several times and I admonished them for that and then we tried to do it on the hose but just not enough water flow and motor was getting hot. We finally took it to the ramp and dunked it but we got a good 20 minutes of run time then with seemingly no issues and then we were trying to sort out some other issues before we took it for another sea trial which is when this happened.

I'm stumped, can't help but feel like something gave way somewhere, I suppose it could be a vaccum leak on carb gasket as it seemed to have a slight idle hesitation when carb cleaner sprayer in one area but it was very slight. Very frustrated

Based on the valve covers, that appears to be 7.4 which is a 310hp version 454 with cast internals and peanut port heads.
The cam is a small upgrade and still smaller than 454mag cam. Nothing you are posting indicates that a lobe got wiped out.
Did the sea pump get new impeller/housing??

Why the heck would they do a JR Marine kit instead of just removing the transom assembly with the engine out??

motor was bought used. I had a different mechanic who ended up being a lying sheister install it. Didn't go through the motor or the outdrive at all like he was supposed to. By the time I figured it out he had literally packed up shop and run. Boat had a ton of other cosmetic work being done so I didn't try to use the boat after getting this motor put in. When I did finally go to try and use boat I had overheat on the dock and also discovered cracked gimbal ring. So I found this mechanic to do gimbal ring repair not knowing I had any major issues with motor. Gimbal repair was done with motor in boat and then motor blew up after.

I have tried looking everywhere for cam specs on Magnum and couldn't find them. Do you know what they are?

It's a brand new pump, impeller and housing. It's like the 4th impeller and housing because one of the many things uncovered through this process was bravoitis. Before we knew motor was bad, we kept getting hot under power. I researched bravoitis and so we installed a thru hull and strainer for cooling. Once motor blew and we took it out we confirmed bad bravoitis and we did the repair so we have excellent cooling flow through the lower unit and the thru hull. Also replaced upper and lower shift cable, throttle cable, inspected y pipe and changed that gasket. On the motor itself we also discovered a busted oil cooler so that was replaced. The only part not rebuilt or replaced on the motor is the power steering pump. We put on a new alternator and starter as well being proactive. Oh yeah, and when we bought the new seawater pump we bought a new mechanical fuel pump too.

I committed to fixing this boat right once I sold my center console last summer and realized that we may just keep and run this boat for another year or 2 until my daughter gets a little older and can more capably fish we will probably be doing more family cruising so I wanted everything like a new boat if I'm gonna be taking my family on it. Its frustrating because I should be a mechanics dream, I'm not complaining or haggling price one bit, just want it done right.

I found the mag cam specs and you are right, they are very similar so that's a bit of relief knowing it's not like I did some crazy insane upgrade. Crossing fingers that it's a random vaccum leak caused by who knows what and maybe a timing issue that will be easy to resolve. Will definitely have them check compression. Fuel has been in the boat for a year but was treated with seafoam when tank was filled. About half the tank has been run, I'll top off the tank with fresh rec90 next time out as well. With the higher compression from the domed pistons could lower octane fuel be contributing to this? Maybe top off with 93 to have octane end up at 90?

One last bit of info I forgot about. When we were idling back to the dock and temps cooked down some we noticed the thermostat housing was super cool as if the the tstat was stuck closed. They took the tstat out at the shop to test it and was functioning fine. A brand new circulation pump was also put on this boat after the rebuild and yes it was a marine circulation pump not a truck pump which I read can be problematic for some reason pertaining to the volume they pump or something of the sort

When a engine overheats I like to replace the thermostat even if it wasn’t the cause. You just took it out of it’s normally operating range.
when an engine “diesels/runs on” they often times run backwards. This can blow off any vac lines or plugs, could also damage a gasket ( carb base /intake) Are you working on this or the mechanic?

Yes the dieseling a d runny backwards had me petrified of water going into the cylinders with this being a 454!!!! Hoping it's a carb gasket and not an intake gasket and hoping it was caused by the improper base timing. Those are 2 easy fixes. Mechanic is doing this but I'm trying to be an "educated consumer".

18 cc domes on pistons with peanut port 113 cc iron heads?? assuming zero deck clearance and heads resurfaced your at 10.2-1 compression with .050 duration of 218/224, hope your running 93, was carb rejetted and adjusted for new combination? you might have problems with running stock timing once its set "normal" if not runnning 93, dont forget, a motor will spark knock in a boat inaudibly over wind and exhaust noise, be careful as you go forward, Smitty

Thank you for this. Plan was to run at least rec 90 but not opposed to running 93 either, just trying to get through the rest of the tank of gas that is in it. I will definitely top off with 93 on Monday morning before we continue to mess with it. Carb was not rejetted but will look into it. Pretty sure it's a 750cfm and I was under the impression it would be fine as is. If anyone else cares to elaborate I'm all ears.

Stock Magnum cam is .510/.510, 224/224 and 115.5 lob sep

Im rethinking your "dieseling/run on issue" and here is my guess at WHY based on my own experiences : IF base timing was actually set at ZERO on top of having a bigger cam, motor would NOT idle/stay idling when fired up. The first thing that was done at that point was the idle stop screw was turned IN until it at least would idle, since timing was LOW, the idle wasnt strong and the throttle blades/idle stop got turned in quite a ways to get a decent idle due to lack of idle timing, (seen this on my dyno) so, when engine was ran then shut off, it was getting all kinds of air , hence the run on. Ive had to drag my dyno brake when shutting motors down on fire up as we get all the adjustments balanced to shut down a motor that wanted to run on, at least thats my guess, Smitty

Today's update
this boat has been a project that has now gone on for over a year. I thought it was Done in January of 2021 and I put a full tank of 87 octane in then. I'll skip the particulars but the boat ran for a total of about half a tank of fuel before motor blew up and we did this rebuild. So I have a half tank of 87 octane fuel in there (it was treated with stabilizer when the tank was filled and we have never seen evidence of water in the fuel) and the mention of the higher compression and the low octane was bothering me. I dont think it's responsible totally but it certainly can't be helping. So I bought some "race gas concentrate" to up the octane to approximately 93. We dumped it in and allowed the drive to the ramp to hopefully mix it up. Got to the ramp and the same high idle condition persisted. That had a vaccum gauge hooked up and we're doing diagnostics ultimately just trying to get the idle down low enough so they could check and set the base timing. We got it to idle around 800-850 and were able to get base timing in the ballpark. The carb was very sensitive to many adjustments they were making, particular the idle screw. It was like the slightest movement would be too much and either stall out or rev WAYYYYY to high.

Ultimately we had it idling decent enough that we decided to go run it and see if we had any overheat issues. We didn't overheat and particularly under load it seemed to stay quite cool, if anything, at idle the temp would creep up and there was definitely varying temps side to side. I know it's common for one side to be hotter than the other on the hose but I thought I. The water it would be more balanced than that. Curious if anyone has any thoughts on that.

When we got back to the dock or anytime we try to put her in neutral she wasn't idling great and would still sometimes stall out. The good thing is we didn't have any dieseling this time out.

I stopped in at the engine rebuilders shop as he is in the same industrial park as the mechanic and he thinks it's as simple as something buggered up in the carb. I can across another thread in my research where someone had rebuilt their carb multiple times and it never worked right but finally he just bought a new carb and that solved his problem. I'm not opposed to that except that apparently Edelbrock marine carbs are just another of the .a y things on crazy backorder

Another night losing sleep researching everything I can on carburetors. I think I may have stumbled onto the problem. It sounds like the cam change is giving us low vaccumn at idle and we have too much spring pressure so its opening opening and allowing more fuel than desired. Kind of explains the sensitivity with trying to adjust idle and getting no middle ground on the adjustment. It would be awesome if it's as simple as that spring change.

I like my mechanic but again as a younger guy he's more about fuel injection but if he's gonna market himself as a mercruiser guy he needs to get familiar with carbs. I think after working on my boat he may become the next mechanic to go "outboards only, 10 years old or less" LOL

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I don’t think the cam is big enough to mess up the fuel enrichment system in carb. Sounds like it is not running on the idle circuit. Haven’t found the vac leak, or carb needs rebuilt.

I don't disagree but I will say this....Carb was just rebuilt in August and literally only had 5 hours use them motor blew and had to be rebuilt. So it's possible it got some crud in it sitting on a shelf in the shop I guess but I'm thinking that this carb was rebuilt to the specs for a factory 330hp 454, not the magnum. In fact, research appears to show that the magnum usually uses a qjet carb. So I really think next step is to definitely at least try the metering rod spring change because the symptoms are exactly as described in the manual and as mentioned in this YouTube video.

Thanks for the pic, however looking for pic with engine installed in boat because rigging is more often than not , people’s issues. Sometimes we catch these mistakes on ohotis.

Did you use the factory weber carb to quadrajet intake manifold in which one side of adapter look like this ? If so, which gaskets did you use ?




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No carb adapter it's a factory intake that has both types of bolt holes

You have pic of top of intake without carb installed ? And casting # ?( My phone can’t clearly show me cast # from your last pic.)

I don't think I do. I did find this pic of motor in the boat though
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https://cimg0.ibsrv.net/gimg/www.off...8612920160.jpg
Found one from when they were de-rigging to pull it out after it blew

approach this problem in steps.
1st verify that the TDC on the balancer is truly TDC, unless you have a brand new balancer. I've had a situation on a boat where setting timing according to the balancer, the engine would not idle unless I cranked up timing. I think the balancer had slipped on. the boat I was working on.
2nd. the carb should run on the isle circuit just fine. Adjust the carb idle mixture screws 2 turns out and set the idle screw as close to closed as possible. Like Smitty said, your dieseling problem is because the primary blades are too far open.
3rd, once you can get the boat to idle on the idle circuit, then do a final verification of timing. 34-36 total above 4000 rpm. you may have to turn up the idle speed screw
initally though.
4th once timing is set work on getting the engine to idle with the least amount of primary blades being open. Youll have to play with the idle mixture screws and the idle speed screw some.
SIDE NOTE: spray carb cleaner around the throttle shafts. If the rpms change drastically, your throttle shafts may be worn out, causing the vacuum leak. When they are adjusting timing, are they using a timing light AND a vacuum gauge?

Yesterday it was a struggle to get the idle low enough and consistent enough for them to set the timing but they seemed to get it. It didn't diesel at all yesterday but it still idled high and ran like crap at idle

Do you still have that fuel tank to engine fuel line and see thru filter ? I hope to god not.

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Here is the metering rod that's in it. Looks to be marked 6542 which isn't anywhere on the chart. I know the chart isn't the end all be all though. I am going to put a pair of the 7347 in as that is the closest to stock. Looking up spring color codes now

Why?
Fwiw, I do have a regular spin on fuel water separator

Has this carb ever ran/performed correctly since it was rebuilt?

Is this one of those merc 454’s with rectangular port intake manifolds installed on ovsl potrt heads ? If so, what intake gasket was used ?

Those gray marine fuel lines are for outboard engines only. Not rated for enclosed engine compartments. Plus, many of the aftermarket replacements (especially , but not limited to,, Atwood) inner liners dissolve and gum up restricting line and everything past it.

Those glass fuel filters are not coast guard legal, and not even good for cars. Never really a good design from when they where invented.

Yes, it worked fine for 4 hours then motor blew up due to old water damage in one of the cylinders

Yes, rec port intake on peanut port heads. I would have to check with the rebuilder on the intake gasket. Thank you for the knowledge on the glass filter. Super easy to swap out this fuel line anyways so we will do it for sure. I am aware of the issues of the older fuel lines breaking apart from ethanol, I don't think that's our issue here. We don't seem to be having any issues at higher Rpms