Hi All,

I have a 1986 Scarab1 that I'm in love with. I bought the boat in 2011 and have slowly been rebuilding it over the years. Last year, the original engine grenaded and cracked the a few of the pistons. Since the motor needed to be rebuilt I went ahead and did a few mods:

New 350 block and internals
062? I believe Vortec Heads
Xtreme Marine 12-236-3 Cam
Summit aluminum intake to fit new heads
Pretty sure the original quadrajet carb
Corsa Captain Call
Alpha one
21 pitch stainless prop

The boat is very difficult to get started and running when dead cold. I often need to hit the carb with a little starting fluid to get it up and running. When the motor is cold it will also randomly backfire (I believe from the carb) when trying to start. Once she gets up and running and warm, I have no problems at all starting her up. Just start in neutral (no revving needed) (no backfire) idle and go with no issues.

The mods have REALLY made a huge difference and the power is very noticeable. I'm really happy with how the boat runs when i'm cruising down the lake at temperature. I have a few questions.

1. Why the backfire when cold?
2. Since I added a lot of power, does the carb need to be adjusted to provide more fuel? How would I know?
3. I'm not certain that the timing is spot on. Like I said, the boat runs great and makes plenty of power for me, but if I'm leaving some on the table from a timing, carb/fuel delivery perspective I want to fix it and maximize.
4. Are there any aftermarket exhaust manifolds I can get that are lighter and more efficient than the big heavy factory manifolds I have now without breaking the bank?

Thanks in advance!

so you changed heads, intake manifold and cam and never checked the jetting?

That's correct unfortunately. I don't know what I'm looking for or at when it comes to jetting on carbs. I've read that the quadrajet is set pretty rich factory and decided to try what I got before changing anything. Outside of the cold start issue, the boat seems to be running pretty great.

I'm assuming that I should be looking for a performance shop in the area to go through my setup and tune it?

that would be the cheaper option before finding a shop to rebuild it after it goes boom.......

Well I spoke with a local well known performance shop and described the issues I'm having and they suggested a rebuild on the carb, swap jets for a little more fuel, and I'm also going to have them check timing while they're at it. Hoping this will clear up any issues I'm having and get the most reliable power out my setup possible.

I appreciate the insight gentlemen!

Ayuh,..... #1, it's probably runnin' lean, 'n if ya haven't set the timin', that too, could be part of the problem,.....

#2,.... Check the Color of the spark plugs, after runnin' at various rpm levels, to see if it's lean at idle, low rpms, 'n high rpms,...

#3,.... See #1,....

#4,.... There are various aluminum manifolds available, if yer runnin' in freshwater,.... I wouldn't go that way, if runnin' in the brine,...
The other alternative is full blown Headers,.... which ain't at all cheap, by any means,.....

Sounds like a lean condition to me. Lean POP

Well known issue with QJet carbs is that they develop internal leaks and all the fuel leaks out of the bowls when sitting for extended periods of time.

This has all been extremely helpful, thanks for everyones input! I'm going to have the carb rebuilt, re-jetted, and timing checked/adjusted by a local speed shop. Hoping all will be kosher with the setup when they're done with it!

Will report back with the difference it makes!