BUP

iTrader: (9)

hitting a wave making a semi lose connection looser ??

Wig nuts on the batteries for connections - all marine OEM manu's yell at those installs. Do not use wing nuts at battery connections - they come loose over time.

Correct info above - trim has it own power and ground. Many people install that power lead at the starter or many install it at the battery or many install it back side of a perko batterey selector switch among other power connections as well. It just depends whom did the installation.

If this boat has a perko or whatever brand battery on / off selector switch - I would make sure all connections are good - clean and tite and corrosion free on the back side of that battery switch. Also make sure none of the connections on the back side of that battery switch are not touching eachother from one stud to another.. .

If batteries are good or new brand new fully charged batteries do not help - I would be looking at the starter and those connections and prob wonder if the trim power lead is hooked there.

Your problem is a voltage drop IMO and not a small drop

35fountain

We checked everything as mentioned in past posts everything checked out fine.We did install another new battery today... I think this more than one issue here today I took the boat out 3500, 4300, 4600 RPMs playing with the trim switches no issues. When I tried to go above 4700 wide open throttle and raised the trim higher then it started bucking popping and holding back. I then disconnected both trim pumps set the drives a little bit above zero and went wide open throttle it held back and bucked .
touching the trim switches did nothing.I believe that's a fuel issue. The carbs are 800 quick fuel carburetors with Holley electric fuel pumps. We're changing he rear Jets two sizes larger today to see if that corrects it. , if so there mght be something wrong with that one carb

35fountain

We up'd the jets to 85 secondary. Engine ran fine up to 4900 rpms and still same problem. as soon as you touch the trim button it studders, pops.. I checked the voltage gauge while touching the trim button and the gauge drops to 12.5 from 14..I double checked that with my boat also and it did the same thing with the volt meter..

SB

iTrader: (1)

So, the Quick fuel carbs where just installed as this issue appeared or have they been on for sometime without this issue ?

Do you guys have a fuel psi gauge ? If not, I would install one. Holley fuel pumps are not the most dependable items...especially in marine installs since you can never get them below the tank to be gravity fed. Where are the pumps installed height ise compared to the tank height and where are they plumbed in compared to the fuel water seperators ? Pic here can do wonders.

Does this boat also have an MSD ignition too buy any chance ? If so, MSD too ? Or something else and state it. And where are the + and - cables hooked ?

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When you state the engine studders when you use the trim, do they studder at exact same time you use the trim or a second or two or more after ?

SB

iTrader: (1)

BTW: I have seen a massive wave impact bend a Holley carb float arm (never would have believed it but it happened somehow) and thus screw up the needle and seat opening/closing....but the driveabilty issues caused by this obviously would not be effected by hitting the trim button.

35fountain

Ok, Please remember this is not my boat so I was going by what my friend explained to me in the beginning of this thread.. The carbs were ?? flowed by the person he originally bought them from new last year BUT they were set up for a 454 385 hp. After the engine block cracked the boat was put away for the season. This year 2 new GM Mercruiser 502 435 long blocks were installed along with Hardin-Marine ready to run distributor and a holley electric fuel pump set at 7 psi max. The timing is locked in at 34 deg. I mentioned to my friend he should call the guy that setup his carbs in the beginning and tell him they are now on a 502. Ok that didn't go well...It ran really well for about 5 to 6 runs..Keep in mind the weather was very hot and humid those days...Now the humidity is low.. The jets that he has in his carb are Pri 74 and Sec 83 with a 7.0 PW. Apparently the setup person tuned it that way
This morning i looked up his Quick fuel carb and the standard jet size is Pri 78 and Sec. 86 with a 6.5 PW... So we will put back the jets and pw today to factory oem specs and see what happens..As for the other engine I guess its borderline and running on the lean side also

35fountain

Today we put back the carbs to oem specs.. Jets and PW's..Seemed to have more power but still popped while touching the trim switches @ 4700 rpms We even swapped the ignition coils to see if any change as per tech support Jegs.com...Ok i didn't think so either..BUT i just learned this evening that there are 2 very large amplifiers tucked somewhere under the back seat...HA!..Now that can cause a huge power drop..Tonight the tachs were jumping all over the place while idling and playing with the trim switches.
To be Continued..............>>>>>>>

Blueabyss

Make sure you have a separate ground for each battery going to the block. Not one ground going from the block to the perco then a jumper from one neg battery to the next neg. battery terminal. Its a ***** to get to but make sure those grounds are clean and tight on the block..
Cheis

Nordicflame

iTrader: (4)

Interesting... Can't prove this yet but may add some data to the conversation. I have a single engine dual battery setup and last Fall I removed one of the grounds off the back of the block and ran it to the other battery ground terminal to test an ECU grounding/noise issue. This did not help anything on that issue, however, I had the boat on the water for the first time two weeks ago and have experienced something new that wasn't there prior to this change... when idling out I ran the K-Planes down to get on plane and now there is a very large draw on voltage (13 to 10 enough to drop idle substantially)
I am going to change this back in hopes of reversing this issue and will report.

cdail28590

iTrader: (2)

On my fountain I had a issue with 1 motor cutting off for no reason and it would restart after waiting a little while. After switching a bunch of stuff around we narrowed it to 2 i. I replaced the ignition switches and my tachs were also jumping all over the place. Disconnected the tachs and no more issues. I don't know if the ignition switches or the disconnecting the tachs fixed the issue. I was told the older Stewart Warner tachs would cause the ignition to shut off.