its better than getting no head at all.:D

we need to get this engine a 3/4 you guessed it,,race cam.:D

"Internet Randoms"
All of us that have tried to help you have:
1) Have at least assembled and tuned our own engines
2) Built engines for others
3) Own Machine shops
4) All have boat motors that RUN.

You come on here with
"You got burned by seller" Lack of knowledge by you
1st engine builder burned you Lack of your ability
2nd builder Knows his stuff but cannot
a) set timing
b) adjust carb
c) diagnose engine failure

and you come on here asking advice and call us "internet randoms"

https://www.riverdavesplace.com/foru...0-jpg.1091514/

Well I did get burned by seller of more but I knew was taking gamble when buying the used motor to begin with.

There was no 1st engine builder that burned me. It was a bad mechanic and I own that as I chose him even though it was based on a good recommendation from a business associate. Needless to say he won't be getting business from me anymore.

As for this mechanic, yes, mistakes have been made. It happens. He has owned them and taken responsibility.

I have no beef with you guys but when your posts go from advice on things to try to chastising the build of the motor it is completely unproductive. What's done is done.

Are you getting back to it this weekend? Anxious to hear end of this story.

I don't think so. I haven't messaged mechanic to see if they made any progress today or not. I'm in Tampa and it's been 80s all week, ramps are gonna be insane all weekend so I don't even want to try to put it in the water anywhere until Monday. Ill be sure to keep the thread posted. One of the challenges when you go searching the internet for people that have had similar problems is when they get them resolved they rarely remember to report back on what it was!!!

80’s…….get out! Freezing rain here this morning. (Indiana)

Haha. You need to book one of my Airbnb properties and get away from that ****!

Www.airbnb.com/h/tampaoasis4
Www.airbnb.com/h/tampaoasis3
Www.airbnb.com/h/tampaoasis2
Www.airbnb.com/h/tampaoasis1
If these other know it alls played nice in the sandbox I'd invite them down for a free stay in exchange for fixing my boat!

I can empathize with your current dilemma and mechanics lack of carbed experience, I have ran into this at my shop quite a few times (we do a mix of stuff including hot rod cars, trucks, dynoing, engine building, transmissions). Im 55 y/o, my son who works for me is 34 years old, he is very skilled and very good with modern vehicles. I trained him and I sent him to school. Thing is, when something shows up that you CANT plug a computer into , his eyes glaze over and he says this is a bunch of junk and even though I have taught him how to tune the stuff he throws his hands up in the air. Then your next problem is even some of the older guys who actually worked on carbed stuff never learned how to properly tune and worked on more stock stuff than modded. so its been listed already but I will list it again, steps to getting tune right. A close friend owns a general repair shop and fights the same battle, a hot rod will come in, his techs are all young and he ships the final tuning out to my shop when they could simply follow a set protocol.
1. inspect for loose, cracked hoses, missing vacuum port plugs,
2. check throttle travel for wide open operation and that it returns to closed with no tension on cable
3.start/ warm up motor
4. check for vacuum leaks, fuel leaks
5. set initial timing
6. set idle using idle stop near your target idle
7. Set and balance idle mixture screws using a vacuum gauge, ie, its warmed up, you turn them 1/4, 1/8 at a time and see if vacuum/idle goes up or down . as it runs better, lower idle back towards target if it starts picking up rpm keep turning them in or out until its no longer gaining vacuum or rpms, then turn them back 1/4 turn if 2 corner mixture, 1/8 turn richer if 4 corner mixture
8. listen for misses at idle or when you rev it up, its very common to see a cracked spark plug on boats that been worked on as some manifolds are very close to plugs, doesn't hurt to pull every plug and just look at condition, have spares in your hands before you do so you don't have to drop everything your doing to go get them
9. IF I was tuning it, before doing wot, cruising test, I would install a 02 sensor and a temporary fuel pressure gauge. Lets say there is some restriction, pumps weak, lines pinched, whatever, if it cant hold within 1 psi of idle fuel pressure at wot, there's a problem. You can install a 02 sensor in a riser, not a easy job but pulling the motor back out after it detonates is a harder job
10. here is a link to the 02 bung that fits water cooled stock manifolds: https://howellefi.com/product/adapto...or-marine-use/
all this is assuming your rotor in distributor is tight, dist caps new or like new with no signs of cross arching, corrosion, your wires are new and work, not burned on a manifold or a boots pulled part way off where spark has to jump inside, etc
11. once its warmed up and all this is done, I would also tell you to use a set back timing light and rev it up and look at total timing, not a bad idea to look at harmonic balancer outer ring and rubber insulator, if swelled up and bulging, theres a chance it has spun outer ring and your timing numbers are incorrect , the time to check that its correct was when heads were off, put motor on tdc with dial indicator, roll .050 down in each direction then average the tdc spot center and look at timing mark vs tab.
lots of other stuff to check but this is what comes to mind
lets revisit your carb: your running some kinda edelbrock carb? I personally hate them things but regardless the typical calibration of most out of box carbs is a little lean for marine applications, I often need to go with bigger jets (or in your case smaller metering rods)to get"safe " afrs.
Safe afrs: your compression is at least one point too high for the cam you have and even marginal as far as detonation on premium, at 10-1 + points of compression with iron heads, the only thing thats going to make this live when torque loaded at wot is a slightly rich afr and conservative timing. we run boost on premium in boats without blowing up by tuning into mid 11's at wot, cools cylinder with the extra fuel. I invested in 10 02 sensor for my dyno, engines with intakes like yours will have a AFR delta of as much as 3 points, ie, richest cylinder may be 11.0-1, leanest may be 14-1 or higher. Thats the cylinder that will turn plug white and break rings lands, melt the top, whatever at wot with what you would think is a normal tune. You dont have the luxury of seeing which cylinder/ cylinders this is now since its in the boat but as I mentioned earlier at one point I dynoed a 502 with similar intake and #3 cylinder was quite lean. So my point is a tailpipe reading of 12.5/13-1 will almost guarantee your 'leanest" cylinder will be too hot combined with your high cylinder pressures from small cam/high compression .
IF I was tuning this less than ideal combination, I would tune rich at wot. Lets say you skip the 02 deal, run it at wot briefly, see your wot rpms, change to 10% smaller high speed needle(makes it 10% richer) run it at wot AGAIN, if it pulls the same rpms, your at least still in the range. Since we're concerned with possible detonation, I would tune richer and richer until it loses rpm, at that point, you've went too far and go back a little. I would tell you to try to color new plugs but unleaded gas doesn't color real well and if you dont have experience with it, you'd prob be left guessing at that point, Smitty AKA- a "internet random", LOL

And some of the banter is not directly aimed at you. Years ago "vortec pro" came on here bragging up his 680 or 750 hp, whatever peanut port headed 454 that had a cam with 30/40 degrees more duration than any inboard boat could ever use, a peak rpm that was irrelevant to a pleasure boating application and a hundred plus hours of porting on the worst heads gm ever made for a bbc to get there, proceeded to debate his skills and build, hence many people that roll their eyes at the mention of peanut port heads on a performance build, Smitty AKA a "internet random"

And ironically I'm smack dab in the middle of you too at 44. My dad was a mechanic as well but due to some health issues he got away from it when I was around 7 or 8 and he passed away when I was 13 so I missed out on opportunity to learn a lot more about this stuff but pretty much everything I ever worked on with him was carbureted ****boxes. My first car was an 83 Pontiac Grand Prix that someone stuck a 305 in then my next car was an 88 grand prix with the new body style and 2.8l fuel injected motor. So I'm right smack in the middle of it.

As for your list, we have already done 1-7 but still unsure on the vaccum leak thing. We need to triple check that. And as for #s 6 and 7 we are having a hard time getting to idle where it is supposed to as a result of whatever has happened which really tonne screams vaccumn leak and with the .I inal amount of vaccumn lines one would think it is a gasket issue.

Regarding carb, yes it's a Weber (Edelbrock 1410 is modern version). We are supposed to test changing the springs, if the vaccine has lowered as a result of the cam change the a metering rod spring change should help the idle however a couple of you guys have mentioned this cam isn't big enough for that to be the cause. I tend to agree because it WAS idling fine then SOMETHING happened. Edelbrock has a chart of what rods and jets to put in to achieve different levels of richness/leanness. I will definitely make swapping to a richer setup a priority.

When I spoke to th mechanic on Thursday he wasn't thrilled at the idea of checking compression again at this point but I'm going to have to demand it. We need to know if we did any serious damage to the motor and it will also give an opportunity to look at the plugs and try to see if they lean/rich etc.

Fwiw, before this motor Fernandes last September we had carb rebuilt by guaranteed carburetor in largo Florida who are well known in the industry. We also put on new distributor cap, rotor and wires so doubtful those are issue since motor had run well after that. Certainly worth double checking wires for getting damaged from heat or something of the sort.

That O2 bung is a nice idea......it will be useful to drop Holley sniper in when I find out this carb is junk hahahahahah

por mans compression test,,can you remember when you were cranking it over,,did it hit on all cylinders and there was not one or 2 missingpulses?
and smitty forgot one,,fuel line collapsing on he inside.

It cranks great and it seems to run really well at Ron's above idle so hard to suspect fuel line

All the more reason for a compression test. Low compression on a cylinder or two will cause low vacuum and poor idle

BTW, timing can bet set at higher rpms easily. If you have a V8-24 module, then set timing to 32* at 3800rpms. Full timing advance happens around 3700rpms with a V8-24 module.

cranking great isn't what I mean,,listen to the engine as compression happens,,does it stay as an even noise or is it missing any time.Its hard to explain.

You mean the rhythm that it makes cranking over?…. It should be steady when
compression is equal, when you have a weak cylinder, the rhythm will change momentarily when that cylinder comes up on compression.

thats it,thats what I was trying to say(albeit poorly :D),,thank you

ummm, if they (mekanic and helper :) ) can’t time engine right or put a decent fuel line on it, this is a little more advanced. No reason not to put compression tester on it.

Btw: still waiting to find out what intake gasket was used.on this rect intake/ peanut butter port headed engine.

You positive this engine brand new oe from merc didn’t use an adapter to seal the carb ? I know the 502 bravo with that style intake and weber carb used one to seal the carb base gasket to intake.


https://cimg5.ibsrv.net/gimg/www.off...7ab486596f.gif

I also know edelbrock used a thinner but similar plate to seal their carbs to their similar performer series spreadbore intakes.

That is the same intake that was on my 1993 454mag with a weber carb and no adapter was used. I also looked it up on mercruiserparts.com and the 7.4 used the same intake for several years in the early and mid 90's with no adapter as well.

Great info. Thanks.

Busy start to my week. Thanks for th info about th carb adapter and the subsequent verification of it not being needed. Short answer, no, I don't know what was on this motor originally.
I was too busy to stop by or call mechanic today but he did do compression test as I asked and he texted me that all holes were at 180 psi.
We are still chasing down a leak in the transom, we think it was the trim Manifold gasket at the bottom. Had a ***** of a time getting it out and of course the new one showed up with a chunk taken out in one of the 4 holes that definitely wouldn't have sealed properly and leaked so we sent it back and hopefully the new one showed up today. So next thing he wants to do is more carb troubleshooting on the water. I'm really feeling like some random carb problem is the culprit and really just want to buy a new one and stick it on but again new ones can't be had right now. Trying to source a known decent working one to test.

Those are sold already

took the carb back to the rebuilders under warranty. They took it apart and send there was some funky gelling in there and cleaned it back up. Bringing it back to mechanic tomorrow and hopefully we can get her out again and see whats what. Will probably top her off with fuel again to get the octane up and make sure it's all fresh fuel

Probably the Ethanol goo (it also crystalizes) from sitting. How long did it sit again ? Aluminum or plastic tank ?

Tank was filled in January 2021 and a gallon of seafoam was added at the same time. Got little use beyond seatrisls and occasional running every couple of weeks while I worked on other cosmetics with the boat. Then boat blew up in September. Carb only had 5hrs of use after carb rebuild before motor blew up. Carb sat on shelf from September until January. Fuel has come up out of tank looking good everytime, no water that we have seen. It's a plastic tank.

After watching the video I gotta say I'm impressed with the power potential with the head/intake port mismatch. Just bumping up the cam made a nice increase. For me, I'd have to go to a forged crank and bigger rods of the Magnums if I added more cam, RPM, and HP. The dyno numbers are great but I like reliability. A boat runs at constant high rpm for a long time while a car rarely does. But I'm surprised that the potential is at least there.

SB is on point. I’ve seen carbs get the jelly goo looking junk and crystallized stuff in just one season. Hope that’s all of your problem.

Verdict is in it was the carb! I wasn't able to attend the last sea trial but mechanic reported back that she ran strong and idled proper. He did discover that the tach itself seems to be acting up. I had changed all the gauges but left that one because it reflected the accurate boat hours. I'll check the connections for corrosion and change it out if I must. We had nasty weather yesterday but if it's decent today I'll pick it up and take her for a run.

Ive seen tachs that are actiing up make a motor run poorly but usually on top end at wot fwiw, Smitty

Thats great. I would have bet money you had a gasket leaking vac. Glad it was just carb and hopefully he stood behind it.

yup or tachs without that issue but needle bouncing or stuck that just need the rear dial for cyl # select slowly turned back anf forth to rub clean it’s contacts. Fixed 2 last year this way. And several others over the years.

I woud have thought a man like you,using a rubber mallet and smacking it a few times.:D

Yes, but that should be in the Pornhub forum, not here. :) :party-smiley-004::hijack::lolhit:

My first car, a 71 gmc 2wd pu with a 350 , stayed stock for like 48 hrs after I bought it in 1982, 80$ black jack headers, aluminum intake, crower cam, you name it and most of it was USED stuff as I didnt earn alot of money during that recession and was in high school. Well, lo and behold, I was at a rummage sale and found a SUN SUPER 2 chrome tach in a junk pile for 3$, well, after installing it, randomly when I tried to hold that 350 to nascar like RPMS (I was 16 or 17) it would randomly breakup at 5000 or something instead of floating the valves at 6000+, I fiddle fukked with ign, timing, plugs, DWELL on points (YEAH) and it would seem to be "fixed" then come back. Well one time when it was not revving for ****, I tapped on tach. Got my azz zapped, somehow it was shorting ignition out randomly. Unhooked wire from the coil to tach, revved to valve float every time, the good ol days!

Update:. Motor still not running right. In the process we discovered the tach was acting up. I took off trim plate to access back of tach, sprayed some electrical cleaner and rotated the thingamajig and put it back into position which seemed to clean the contacts well and now has tach seemingly Active. No jumping around when tapping on it. Boat runs good up to about 3200 rpm which gets me 30-32 mph (sea ray 260 sundancer so solid numbers for a heavy cruiser). When giving it more throttle I hear motor get a little louder but little additional rpm maybe gets to 3500 and no more speed.

Additional things we have done are as followsBrand new Edelbrock carb, many times rebuilding carbs just doesn't seem to work and a new one is in order. Didn't fix issue, same thing.
Troubleshot fuel delivery, no antisiphon valve at the tank just a hose barb, clear flow. Took out tank pickup it's in great shape.
Replace fuel line from tank to fuel pump and eliminated that small glass fuel filter. That seemed to make idle a bit better as we were having trouble getting idle down to 750, seemed like it was sucking a little air. Once fuel line change was easily able to get idle adjusted down but still nothing on top end.
Swapped out stock fuel pump which was new and replaced with a Holley 110gph higher flow. No change. I think we have ruled out starving for fuel.

Next thing I'm trying is new plug wires, hard to believe but somewhere in all of this engine rebuilding and what not new wires were NOT put on. I believe it was an oversight due to product backorders. Wires were something we wanted oem and couldn't get them and got forgotten about. I just put new wires on and will try sea trialing tomorrow. If that doesn't fix it I believe it's down to 2 things the thunderbolt module not advancing timing or some problem with the valve train. Anyone have any other ideas? I ordered a marine HEI distributor and want to eliminate the thunderbolt 4 but honestly, I don't know if this distributor can. E changed with the engine in the boat. I hope I'm wrong about that

Also should add that we have worked out way through all the old fuel from January of 2021. I have since put in 50 gallons of 93 octane. Not ethanol free but seemed like I should focus on having the higher octane with the engine parameters vs no ethanol. While I understand that low octane fuel can cause problems, it shouldnt prevent the motor from revving past 3500.
FInally, I'm far from an expert but nothing about th motor sounds bad. Idle seems smooth and it runs good up to that 3000 rpm mark then it just won't go. I changed wires today, I suppose I should pull plugs and double check gaps on them too?

What made you or he think it was fixed below?

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