fkboatman

you really need to get a timing light with a advance. and run motor to about 2500 0r 3000 rpm and see what you get for total timming. either your not getting enough total timming or your lean. and with it miss firing around 2k rpm. i would say its running lean. Do you have anyone locally can help you dial this thing in or even the guys at the machine shop shoukld know basic engine tunning set up like we bein talking about.

Pliant

There ya go merc is a weber but same metering rods...Try two or three rods richer..Should be spot on..with 26 degrees total timing..

Edited to 26 degress 8 at the base

speedboatr

Just getting back in town and hope to try the new rods in the next day or so. I did use a timing light with advance. Also borrowed a bypass module that plugs into the distributer to set the timing to 10 BTDC. Can I now check the total timing by running the motor at 3000 rpm with the bypass module removed, correct?
I also found the ederbrock info helpful but the 600cmf marine carb info is based on the stock set up and using the 89 jets rod set up they recommend with a 4.3 is off the chart shown in the book. You can see what they are doing and kind of guess what to do, so that’s where I came up the .63 x .47 rod to try next. The 68 x 57 rod they recommend for the 4.3 is worse than the 68 x 47 rod that came in the carb stock. So I’m hoping the 63 x 47 rod does the trick.
I will let you know how it goes

Thanks again for all the help!
Speed

fkboatman

correct about timming set up. i would pull the 89 secondary jets and change to min. 92 like you said early. but definately change out the rods. rods control mid rpm range.

speedboatr

Hi Guys,

I did get a chance to run the boat this past weekend however not enough time to check everything. The mid rpm runs fine with the 89 primary jets, pink springs and 63 x 47 rods. I also changed the secondary jets to the 92s ,however I still have an issue with wot, it tops out at around 3,900 to 4,000 with 1/8 or so throttle to go (throttle seems to be a little closer to the wide open position than before?, but still not right). Actually when you go to wot and back off to the point that rpm matches the throttle position you gain 50 to 100 rpm??? Unfortunately another problem surfaced when testing the boat…. A bearing is going out of the jet drive and before I take the boat out again it must be fixed. i think soon I will be able to take the scarab back to the factory and have it titled as a 2010!!

Thanks for all the info.
Speed

fkboatman

you really need to find out what your total timming is.

ZXXX Donzi

It does not like the Edelbrock Carb at first. Stay with it though, you can do it. I got it on my second round. I would still like a smaller carb but it was an easy option.

I did the heads, cam, carb, intake and IMCO exhaust on my father's 4.3. It really woke it up. It needs boost now.