HELP with GM 350 timing

[Amurich]

Hello,

I have a 32' Thompson with what an engine that says GM 5.0L B on the block. I asked around and was told that it's a GM 350 engine. On the flame resister on top of the carb, it says Volvo Penta AQ 231B. I am trying to figure out what is the proper timing on that engine. I just set it to "8 before", it's working alot quiter, but I can't get the RPM to go up above 2700 at full throttle with stern drive in gear. Before I could get it to 3200. And I am being told that the normal operating RPM for that engine should be 4000-4500. I have Aquanatics 290 Stern drive with 15/19 single props. The boat is dual engine/single prop, by the way. Also, the intakes were replaced with Edelbrock performance intake and it has 600 Edelbrock carbs. Any help on the subject would be greatly appreciated!!! Many thanks ahead of time.

Dimitri

 

[AdamB]

Re: HELP with GM 350 timing

I'm sure you're going to need the casting #'s on the block to be sure what you have.

My mercruiser book I have talks about either 6 or 8 BTDC for timing depending on which 350 you have. I don't know abou tjhe 305 engines.

What did you have the timing set at before? What idle rpm are you setting the timing at? I would say you should be able to rev alot higher than you do with 19 pitch props...

 

[Bondo]

Re: HELP with GM 350 timing

"The boat is dual engine/single prop, by the way."

I know that Volvo has built some Unusual Drives,.......

But this Really Confuses Me..........

And,...... By Your description,...... You've got a 5.0l,... Not a 350....

 

[Amurich]

Re: HELP with GM 350 timing

Well, I was setting it with idle RPM at about 850. I know about the casting #s, but due to the fact that it's a twin V8, it's litterally impossible to locate them. There less room in the engine compartment then under the hood of any 2006 vehicle.
I have another thought, but I am not sure how to test or prove it. I am thinking that the secondary chambers on the carbs are not kicking in. How do they work and how can i make sure that they are working?

 

[Amurich]

Re: HELP with GM 350 timing

"The boat is dual engine/single prop, by the way."

I know that Volvo has built some Unusual Drives,.......

But this Really Confuses Me..........

And,...... By Your description,...... You've got a 5.0l,... Not a 350....

Well, as you can tell, I'm a newbie with the boats and engines, so I am not sure. One thing i know for a fact is that I saw GM 5.0L B on the block. If that helps

It has two V8 egnines. Outboard sterndrives. and a single prop on each outdrive. Don't know how else to explain it

 

[Don S]

Re: HELP with GM 350 timing

If you go to this link, you can download an owners manual for your engine. It has all the tuneup info in it.
You will need to look at the dropdown menu under marine engine and scroll down to AQ231A (NOT B) The A and the B were the same except for the drive. Everything engine is the same.

http://www.volvo.com/volvopenta/global/en-gb/marineengines/operators_manual/operators_manual.htm

Before you set the timing, make sure the point dwell is set first.
Regarding your rpm problem, is it the same on both engines? Have you done a complete tunuep on the engines lately?

 

[AdamB]

Re: HELP with GM 350 timing

Oh that should help those that understand volvos. I at first thought you have a single prop that was turn by both engines coupled together..

 

[Amurich]

Re: HELP with GM 350 timing

If you go to this link, you can download an owners manual for your engine. It has all the tuneup info in it.
You will need to look at the dropdown menu under marine engine and scroll down to AQ231A (NOT B) The A and the B were the same except for the drive. Everything engine is the same.

http://www.volvo.com/volvopenta/global/en-gb/marineengines/operators_manual/operators_manual.htm

Before you set the timing, make sure the point dwell is set first.
Regarding your rpm problem, is it the same on both engines? Have you done a complete tunuep on the engines lately?

Don, Thanks for the link, i'll be sure to check it out. Yes, the tuneup was done and it's the same issue on both engines.
And, i hate to ask, but what is the point dwell?
Thanks

 

[Don S]

Re: HELP with GM 350 timing

Dwell is the angle (in degrees) that the points are open. It's measured with a Dwell meter. Most automotive stores sell them for next to nothing and it's the best way to set the points on a marine engine. Gapping the points is only good for getting it close enough to use the dwell meter.
If all you have ever gotten out of either engine is 3200 rpm, I would bet you are either way over propped, wrong props or wrong gear ratio in the drive or even the trim pin or trim is too low in your outdrive causing the bow to plow instead of ride over the water. Do you have hydraulic trim and a trim gauge on your drives?
After lugging the engine (High load and low revs) you may have a fairly worn out engine. A compression check would be in order.

 

[Amurich]

Re: HELP with GM 350 timing

Dwell is the angle (in degrees) that the points are open. It's measured with a Dwell meter. Most automotive stores sell them for next to nothing and it's the best way to set the points on a marine engine. Gapping the points is only good for getting it close enough to use the dwell meter.
If all you have ever gotten out of either engine is 3200 rpm, I would bet you are either way over propped, wrong props or wrong gear ratio in the drive or even the trim pin or trim is too low in your outdrive causing the bow to plow instead of ride over the water. Do you have hydraulic trim and a trim gauge on your drives?
After lugging the engine (High load and low revs) you may have a fairly worn out engine. A compression check would be in order.

I don have a hydraulic trim, but no meter. it's just a switch

 

[Don S]

Re: HELP with GM 350 timing

Then you don't have a 290 drive. The 290's had hydraulic trim. You either have a 275, or 285 drive.