South Bass fish school with engine question

We started off casting south of starve. Marks were poor at best and only pulled one decent fish in 2 hours of fishing. Decided to pick up and move towards D can and work to green or rattle. When moving past the weather station off south bass, I started marking fish. Marks were great in through the area close to the weather station. We decided to throw the boards out and troll Fish were stacked in the 33 foot of water from the bottom to about 10 foot. After getting about 3 rods in the water off the big boards, my first one fired on a 40 jet 80 back. 27 inch fish. The boat started acting up on low idle and wouldn’t hold speed. Pulled the equipment back in and really couldn’t drift because the wind had died. Casted erie dearie’s and managed 3 more nice fish. It was disappointing to find a nice school of fish and not be able to work them! Better than work I guess.

Question
We have a 2001 29’ baha with a 8.1 volvo penta engine. We have all the trolling bags and necessary equipment to get the boat slowed down to troll. The boat at low speeds 1.1-2.5 mph will load up, cough and sputter than will surge ahead to 3-4.5 mph pulling all the lines off the big boards. We have had one of the better known groups around bass haven work on the boat and supposedly fixed the issue twice and it hasn’t worked. It’s getting frustrating driving up 2.5 hours to find out that the boat hasn’t been fixed and that you cannot troll for fish. Any thoughts as to what could be causing the issue?

Quite possibile you have water in your fuel tank might be worth a shot depending on how much fuel is in the tank dropping a couple cans of sea foam in there. Another quicky would be a loose plug wire or bad plug.

2001 is likely fuel injected otherwise I would say sticky floats.

Just off the top of my head without any research

Bad choke solenoid...

Engine just a tick out of time...

Sparkplug wires arcing somewhere...

Sparkplugs not gapped properly...

Too low of octane of fuel...

Water in the fuel system...

Restricted airflow to the intake system...

Hard telling without seeing more syptoms (like soot color on the plugs and exhaust color when the engine finally catches up)

I would go with the simplest first. Replace plugs and wires (gap plugs according to manual), check for anything obstructing airflow to the intake, and use an octane additive in your fuel. After that, if it doesn't fix, I would figure how to disconnect the choke system easily and do that.

I don't envy you man. This could be either electrical (ignition system) or fuel system related.

Good luck!

clogged fuel filter(s) ?

Thanks for the reply fellas…. We have hit it with dry gas (tried that before we discovered sea foam … may have to try that now too) and we have replaced all the plugs and wires. I believe the choke solenoid was replaced as well.
On my Thompson 240 which is a 5.7 merc, the carb had to be adjusted (re-jetted?) to troll at slow speeds. I wasn’t sure if there was an adjustment that needed be done the big block 8.1 volvo to enable slow speed trolling or if in fact it was an issue such as water in the fuel or what you had listed B-Can Man. The boat was originally set up for salmon fishing off of Lake Michigan

The best thing to do would be to have the codes stored in the computer read to find what is actually wrong before throwing money at it on the theory that this might be the problem or it could cause the probleml. It could be as simple as a fuel pressure regulator.

Is it a carb or fuel injected?

That is a 496 cid GM big block, it is almost certain that it is multiport fuel injected with a contol modual/computer. Those engines and electronics have a very sofisticated electrical system that have a large amount of sensors that must be in working order for it to run properly. Save yourself some time and money and have the codes read.

Def fuel injected. Thanks for the input. We just called another group in to look at it and I asked if they could put a computer on it and read the codes and they said that they would defiantly do that. We are going to have them check the fuel filters as well.

With an EFI engine that is not running right it is really hard to diagnose with out reading the faults. The EFI will try everything it can to make the engine run correctly given the information it has received from all the sensors even when a sensor is sending bogus information. I don't think you will be able to hood up a standard autozone rental OBDII code reader, rather I believe it uses a CAN bus style plug.

I am not sure if Volvo Penta uses the same ECM that Mercruiser uses or not, but the ones Mercruiser uses are, I think, furnished by a GM supplier to operate the engines made by the GM Powertrain Marine division which are then supplied to the different manufacturers ready to install. Most of the differences are cosmetic in nature as well as some of the accessories such as water pumps and other external engine parts.

In any event if the code check comes back negative and the ECM does not monitor fuel pressure before reaching the injector banks, then it is most likely in the fuel delivery system. Which consists of the fuel pump and the fuel pressure regulator or in some cases a second regulator when there is one on each bank of injectors and mounted on the injector rails. The engine is designed to operate on a certain amount of fuel pressure and if it is to low the engine will not operate correctly. Most of the time when the engine seems to run fine at higher RPMs and then wants to die at idle there is a fuel pressure problem which may or may not show up with a code scan. Almost all other problems will be recorded in the ECM's memory bank.

Remember this is nothing more than a standard GM engine that has been made suitable for marine use with the likes of brass soft plugs, exhaust manifolds and other superficial things that make the engine safer in a marine atmosphere as well as more corrosion proof. The parts that make it run such as fuel pressure regulators, and other sensors are the same ones available at the GM parts department and used on street vehicles! When you remove a sensor from the engine the part number stamped or molded into it or on it will most often be identical to the ones in the GM service manuals for cars and trucks at less than half the cost. Alternators, starters, coils and distributors must be spark proof to meet Coast Guard safety requirements so they are different but are available from GM suppliers and other outlets at reduced cost. In other words you are paying for the name of the engine supplier.

I do not no the first thing about motors!My Buddys boat has an older Ford motor in it.He had same issue with it loading up with gas etc. Had it worked on several times.Boat ran great when running from here to there.As soon as he tried to slow troll,is when it acted up.Couple-3 years ago he bought a smaller kicker motor for trolling.It has been the ticket!He recently purchased an extended handle(tiller?)Takes some time to get used to.But will be much more comfortable to work with on long hauls.NO mechanic here,maybe yours just needs an adjustment?Good luck with that,and the fishin!!!