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TonyB
05-28-2011, 10:18 PM
I have 91 Prostar 190 with 351 Indmar. Near the end of last summer, after stopping to get a snack at a riverside restaurant, I came back out and cranked up the boat and found that at low rpms I had a terrible engine vibration. Everything cleared up once above 2000-2500 rpms. Thought maybe a vacuum leak but could never find it.

This spring I rebuilt the carb just in case. Put the carb back on and cranked it up. Seemed to be "better" but not great. I pulled out the timing light and checked timing and was, according to a "pin" next to the harmonic damper, running somewhere around 20 deg btdc. I knew it was supposed to be 10 degrees btdc so I reset it.

Get out on the water and give it gas and it stalls and backfires through the carb. Keep trying to get it up on plane but it always dies when given some throttle. Just happen to take the timing light with me and try to adjust it back to where it was. I've got it somewhere around 18 degrees btdc right not and it will reach a plane but not without going through a rough patch during 1st half of throttle.

What about my 351 could be different that would make 10 deg btdc incorrect? What is the correct timing then? There is a mark at 10deg indicating that is what was used in the past.

I'm the second owner and have had it for about 8 years.

Help.

1redTA
05-28-2011, 10:48 PM
are the weights and springs in the distributer free?

TonyB
05-28-2011, 11:13 PM
Hmmmm. I do not know. At the beginning of last summer I replaced the EI module. Maybe I effed something up.

TonyB
05-29-2011, 11:34 AM
Weights and springs are free but the springs are tight. However, I could never get the timing to advance more than 2-3 degrees when throttling up.

JimN
05-29-2011, 11:54 AM
Weights and springs are free but the springs are tight. However, I could never get the timing to advance more than 2-3 degrees when throttling up.

Replace the springs.

Does your distributor have a vacuum line going to it? Make sure it's not kinked, clogged or leaking.

TonyB
05-29-2011, 12:17 PM
No vacuum line.

TonyB
05-31-2011, 11:52 AM
Oh well. First time ever for me give up. It's in the shop.