AQ125A Hesitation

"First of all, here's what

"First of all, here's what's been done on the boat:

New alternator
New battery
New plug wires
New plugs
New rotor
New distributor cap
Timing checked: 10º BTDC @ 900 RPM, 36º BTDC @ 4000 RPM
New impeller
New Fuel pump
New inline fuel filter
Carburetor Rebuild kit
Lots of seafoam run through engine

Running the boat in the driveway in neutral, applying full throttle causes the engine to stumble and die. If I give it a bit of throttle (to take to around 2000 rpm) and then open the throttle wide open, it hesitates and then gains RPM. Even running at 3000 RPM, when WOT is applied, it hesitates for a second and then gains RPM.

I've checked the accelerator pump and it's squirting plenty of fuel into the carb throat. I haven't checked the engine compression yet, could this be the cause? Timing was spot on when I checked it. I was thinking about sourcing a Pertronix ignition conversion, maybe this may have some effect?

It's probably worth noting that when the engine was run on 87 octane fuel, the hesitation was almost non-existent. However, the engine pinged quite a bit on 87 octane fuel. Currently, it has 91/93 octane fuel in it with some octane booster as well. I'm wondering if this could be a bit too much octane?

Also, when I put the flame arrester on the carb (actually, just the plate with the crankcase vent tube attached), the engine runs considerably rougher. Is this a symptom that something is wrong deep inside the engine?"

"Check that there is no delay

"Check that there is no delay in the squirting from the acceleration pump. You can adjust this at the carb.

Higher octane will not affect negatively the engine's performance.

Also, check if there is a lot of blow-by gas coming from the crankcase vent. If this is the case, then it may be time for rebuilding the engine."

"Thanks El Pescador.

I to

"Thanks El Pescador.

I took a look at the accelerator pump one more time. It was working for the most part, but I realized there was a washer missing from the shaft (it's never been there since the boat came into our possession). I put a washer on there to give the spring a bit more compression and sure enough, the hesitation is vitually entirely gone.

As far as the blow-by gas from the crank case vent, I can literally see a mist from the vent when the engine is warm. I'm going to check the compression tomorrow and see what it tells me."

"Adam, I'm glad you are ge

"Adam, I'm glad you are getting things under control. Regarding a bit of mist coming from the crankcase vent, that's normal and should not be a concern. But when there is a lot of blow-by gas coming through the vent, that is a sign of a very tired engine (worn cylinder walls, piston rings, etc). Hopefully, this is not your case. Also, a compression test will give you inconclusive results, as compression can be lost through intake or exhaust valves, piston rings, etc. You may have to run a leakdown test to pinpoint where you are loosing compression if the engine compression readings are not satisfactory."

"Thanks El Pescador.

The en

"Thanks El Pescador.

The engine is running great, but unfortunately it has a lot of symptoms pointing to be a very old and tired engine and will probably require a rebuild this winter.

The oil quality has been degrading everytime the boat has been ran - it looks like water is mixing in with the oil. Crap."

You can do what other people h

You can do what other people have done: get a B21 car engine (from a 76-82 240 Volvo) in good condition and marinize it.

"Thanks for the tip.

I gues

"Thanks for the tip.

I guess we'll figure out where the leak is and how serious it is before decided to rebuild, replace, or sell.

I read up a bit more on the leak-down test and that sounds like the ticket. I'll make a tester tomorrow and see what it tells me."

"I pulled a B21 block from an

"I pulled a B21 block from an 82 Volvo 240. It was freshly built, but had tranny problems. Got the short block for 175 bucks, and transplanted my marine head and intake/exhaust....... Works awesome!"