checking the automatic advance on a volvo penta 260B (350block)

[OnaRampage]

I've had a perpetual problem all season and limited time to try to fix it. The engine was rebuilt last year and ran great putting on about 200 hours. The symptom is normal running up to about 2500-2800 RPM then severe chugging. Like running out of fuel. First thought, my Rochester Quadrajet. But it's not that. I've tried 4 different new (rebuilt) carbs and all the same thing. Changed carb, plugs, rotor, cap, fuel filter (many times), drained the tanks, put in high octane fuel. Then I checked the timing. It was off a bit so I readjusted it to 4* before TDC. But upon checking it at higher RPMs it does not advance. It actually falls way after and gets quite jumpy. At 1500 RPMs it is running at about 2* after TDC and at 2500 RPMs it is running between 6-10* after TDC and is very jumpy. I think I'm looking at a distributor problem as it was with a few other accessories pulled and reused from the old engine. I'm at a loss, and getting very frustrated! Any suggestions? Thanks- Glen

[BigosS]

If you can do this safely, try moving the distributor while running to see if you can reach full RPMs without any pinging. Post the year and configuration of your engine (electronic ignition?), and you may get more ideas.

[OnaRampage]

My boat doesn't have electronic ignition. The boat is 1987 straight inboard Rampage. The engine was rebuilt the beginning of last year and ran great all year. It is a volvo penta 260b series. I was told today by someone that this type engine does not have any mechanism to "advance" the ignition. I'm at a loss as for why I get the problem I have. This engine just isn't that complicated. Any help would be great. - Glen

[Stickbo]

I have the same engines. I wish i could help with the problem, unfortunatly i am just learning them. Sorry to be a little off topic just wondering what it cost for the rebuild? Probably going to have them done this winter.

[baitkiller]

Its mechanical only, no vacuum or electronic advance. Put a timing light on it and rev the motor, see if the spark advances. If it doesn't move, pull the cap and service the flyweights located under the breaker plate. Then use an advance light to set the timing at full advance. I cant remember the degree setting, check the manual.

[BigosS]

Here is a link for some 350 timing specs
http://www.marineengine.com/discus/m...s/3/9202.shtml

Although this is for a Mercruiser with electronic ignition, you motor should still be about in that range. I looked it up because the OP sounds strange, timing should be BTDC, not AFTC. I agree with the poster above, you might have flyweight problems, also possible timing chain problem (unlikely) or an issue with the plugwire/plug, double check that you are connected to #1. I don't know of any reason for your timing to retard at speed. Sounds very strange.

[Sleeper]

baitkiller has it right, the distributor relies on the centrifugal force of small weights to advance the timing. Pop of the cap and rotor and check to see if the weights and pivot points look rusted up. A good cleaning and light lubrication can easily get them free. Do not put a bunch of grease in there, some WD-40 and a little wire brush will do the trick, dry everything with paper towel when you are done. That engine will definately have a BTDC initial timing, the 350 runs well on advanced timing in the
8-10 degree range as long as your fuel can support that without detonation. A timing light and a few revs will tell you right now if the timing is not advacing.

Best advice is to change over to an electronice distributor in the long run, for about $150 you can greatly improve your antiquated distributor.

[billinstuart]

You should have about 24 crankshaft degrees of advance in the distributor. Sounds like stuck mechanical advance system. I've gotta distributor machine and rebuild distributors. I'd pull the rotor and put penetrating lube on the felt piece..this lubes the shaft the advance pivots on. Weights could also be stuck. Delco HEI has all the advance mechanism under the rotor, others are under the breaker plate.

In any distributor you should be able to turn the rotor by hand about 12 degrees.

[OnaRampage]

Awesome advice. Thanks everybody. I will pull the cap, rotor and breaker plate and see what I find. I'll check back and let you all know what I find. - Glen

[A1 Outboard]

Is your motor a left hand rotation? If so, you have to remember that orientation when checking the timing marks.

[OnaRampage]

Checked and readjusted the timing. Set at 4* BTDC at idle (800 rpms). Looked under the plate in the distributor and while the plates look a little dirty, they move relatively easily. The only weird thing I noticed is that one of the two springs is larger than the other. Don't know if that is normal. Tried a run up again. Same thing. Runs normally up to approximately 2500-2700 rpms and then it runs like crap. We checked the timing and it's all over the place at that rpm and the engine is running like it is running out of fuel. We tested for vacuum at the carb and it seemed low at that rpm, so maybe not enough fuel is getting pulled into the secondary? As more throttle is applied above 3000 rpms, the engine runs worse and worse and starts to lose more and more more rpms until full throttle is acquiring about 2500 rpms instead of 3600-3800 that I used to get. Not sure what to check next, but we're going to run a compression test on every cylinder next. The engine only has about 200 hours, but I'm not sure what to look at next. I'm afraid to spend the $$$ on a new distributor only to have that not be the problem. Any more suggestions?

[richinct]

Sounds like high voltage breakdown. Check the coil, look for cracks in the nipple where the coil wire plugs in, could be arcing out to one of the terminals did you change the plug wires? Run it in the dark and see if you see any arcing, if a wire is cross firing that could give you crazy timing readings.

[baitkiller]

OK,1 If you answer No to any of these, the carb (I'm guessing its a quadratoilette) requires rebuilding. Pull the flame arrestor off and look in the small venturi holes. Move the throttles to full (engine off) There should be two solid streams of gas squirting down into the holes out of a little upside down squirter nozzle doo dad. , Run the engine in neutral and look down the small holes at around 1500 rpm with choke open. Is there constant gassy mist spraying (sucking) in from a different hole than the first time? Both small barrels. Now look down the larger secondary holes and goose the crap out of the throttle. Again you should see a good spray of gas being sucked into the venturi, all four barrels now, when its goosed.

[conehead39]

Borrow or buy an old 75~82 HEI distributor and install it.
Check first if there is enough room , because the HEI has big diameter cap and body.
Run it with the engine cover off because it is not a marine distributor.
If it runs good then:
1.Maybe your Volvo ignition module is bad( assuming it is not a points distributor).
2. Consider buying a new marine disributor.

Never seen a distributor with different size springs used together.
I have seen racing distributors come with 3 sets of different strenght,which help to control the rate of advance.

While you have the engine cover off running it cruising ,remove the carb flame arrestor.
Look down into the carb and see if the secondarys are opening ~3200-3500.
See if they are playing games ,ie opening then closing,ie cycling.

Also the fuel supply from the fuel pump . maybe its getting tired or fuel filter.
Check or replace the fuel filter entering the carb , Behind the fuel fitting carb inlet, if it has one.

http://store.summitracing.com/egnsea...+115&y=14&x=36

[billinstuart]

The springs are progressive. The stiffer one shouldn't come under tension until the advance is part way in. The stiff spring should have some free play at the end with no advance.

[miike]

yeah theyre progessive. did you take the springs out and make sure that everything moves smoothly and is not rusted in place? if they have any corrosion sand them and put a drop of oil them. how dirty was the distributor? did you do a new cap and rotor?

[OnaRampage]

The cap and rotor were replaced. It was dirty in there but everything moved freely.

Conehead - I don't really have access to borrowing another distributor.

Any ideas what a new distributor should cost?

[conehead39]

You don't read real well.
I gave you Summitt link.
I will do it again. When it opens scroll down .
The first three are NON points ; big block and small block.They interchange.

http://store.summitracing.com/egnsea...+115&y=14&x=36

If we still think it is an unstable advancing distributor ,try this.
Remove the weights or wire them both open or close. so They can't move.
Set the timing at 15 degrees advanced ( fixed). May be hard to start ,so set it at 10 adv ,crank,and tap it forward while running to 15-18 go run it. If stable cruising then buy a new distrib.

Back to fuel. The bogging could be the rear secondary jets are clogged.
They can get that way if you don't periodically get into the secondary rear barrels, cleaning out the old fuel in the rear bowls.
With flame arrestor off you can literally see fuel spraying in those rear venturies.SLURP.

You can do both during same run with engine cover off.

A-1 , the cut on the camshaft gear is reversed on LH rotating engines.
LH and RH use the same distributor. view from the top w cap off both are CW rotation.

[conehead39]

Read this link . You don't have a vacuum advance but have centrifugal advance . Read what is says about worn bushings, springs, etc.

http://www.aa1car.com/library/distributor.htm

Spark advance and distibutor wear..

First MSD dist in Summit requires an external ignition amp/module.
First Mallory and Second MSD are drop in units.
Read the details.

[OnaRampage]

Thanks for the replies conehead. I'll check the links and let you know what I find out. At this point I don't even care what the problem specifically is, as long as I can diagnose it and fix it. - Glen