erikgreen
Captain
- Joined
- Jan 8, 2007
- Messages
- 3,105
Hey - I'm posting this to try and help out a friend whose boat we used this weekend for diving. It's a 30 foot trojan, 1979, with dual Chrysler 318 inboards, one LH one RH, and four barrel Carter carbs.
He had the engines rebuilt in 2004 and 2005, along with the carbs. Since the rebuild, he doesn't get full power out of the engines. WOT is between 4000-4200, and up until yesterday he usually got them up to 2500 or so max, top boat speed of 19 knots or so. When he bought the boat it did 30.
Yesterday, I took the flame arrestors off the carbs while he ran them so as to watch the carbs' jets, and found that the back two barrels opened up at a certain throttle setting or above, but never received more than a few drops of gas.
I adjusted the mixture screw on the starboard for the back barrels open three turns and was able to get more gas to flow through the back injectors (a fast dribble), to the point where that one engine got another 600-700 rpm at the same throttle setting. The other engine's back barrels did not receive any gas regardless of how far I turned the screw. Also, the gas did not spray into the little ring like the front barrels, it only dribbled in.
FYI, we also re-adjusted the timing to base spec - 2 degrees BTDC - this weekend. The engines were running at 4 degrees after until today, but they do sound a bit better now. Same performance problem either way, though.
So, does anyone have any suggestions? Specifically we'd like to try to do something that doesn't involve removing/rebuilding the carbs if possible. Today we ran 1 can of sea foam through each engine's gas tank in 20 gallons of gas, and we tried spraying some gumout into the bowls and into the jets.
Thanks,
Erik (Posting for Shawn)
He had the engines rebuilt in 2004 and 2005, along with the carbs. Since the rebuild, he doesn't get full power out of the engines. WOT is between 4000-4200, and up until yesterday he usually got them up to 2500 or so max, top boat speed of 19 knots or so. When he bought the boat it did 30.
Yesterday, I took the flame arrestors off the carbs while he ran them so as to watch the carbs' jets, and found that the back two barrels opened up at a certain throttle setting or above, but never received more than a few drops of gas.
I adjusted the mixture screw on the starboard for the back barrels open three turns and was able to get more gas to flow through the back injectors (a fast dribble), to the point where that one engine got another 600-700 rpm at the same throttle setting. The other engine's back barrels did not receive any gas regardless of how far I turned the screw. Also, the gas did not spray into the little ring like the front barrels, it only dribbled in.
FYI, we also re-adjusted the timing to base spec - 2 degrees BTDC - this weekend. The engines were running at 4 degrees after until today, but they do sound a bit better now. Same performance problem either way, though.
So, does anyone have any suggestions? Specifically we'd like to try to do something that doesn't involve removing/rebuilding the carbs if possible. Today we ran 1 can of sea foam through each engine's gas tank in 20 gallons of gas, and we tried spraying some gumout into the bowls and into the jets.
Thanks,
Erik (Posting for Shawn)
