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softhds1
RO# 11311
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 Posted - Jul 01 2012 : 16:44:43
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My sunrunner with twin 305's ran great until last week. We were down to a quarter of a tank, and all of a sudden both engines will not rev over 3000 rpms. Both motors run smooth and start right up. I just changed both in line filters, added starbrite, and filled up the tank and no change. Whats the next step
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| Paul Joseph |
Homeport: NY
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Brite Idea
RO# 12714
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Posted - Jul 01 2012 : 18:50:00
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carbs or fuel injection? oyher than running the tank low have you done any recent work?
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Homeport: Copiague, N.Y.
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softhds1
RO# 11311
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Posted - Jul 01 2012 : 19:30:09
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carbs, nothing new has been done other than batteries
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Homeport: NY
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zane
RO# 19940
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Posted - Jul 01 2012 : 21:30:44
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Don't discount a dirty bottom.,especially with both motors exhibiting same symptoms.
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Homeport: long island, n.y.
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Sandy
RO# 1159
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Posted - Jul 01 2012 : 22:21:31
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Are these 2 engines running off a single tank with 1 vent, 1 pickup tube & sock, 1 anti-siphon valve and 1 or 2 distribution line(s) leading to 2 flters and valves? If so, check all the 1's.
Do you by any chance have an active RPM sync system connected to these engines ( like my great AccuSync, or the Glendinning system), so if the master engine is RPM-restricted due to any of many potentail issues, the slave will be limited to that RPM as well?
Since they are carbs they probably don't have "Safe Mode" RPM limiting, and that type of limit usually only allows up to ~2000 RPM anyway .
How recently before the issue had they run properly up to full revs , and what figure was that? Were they running fine , then became limited in the middle of a cruise? Or right off the bat after not using the boat for a while they would not rev out?
When you changed the fuel filters, did you inspect the old contents by eye and smell?
As Zane says , only I'd look at the props 1st . Maybe even confirm no one has swapped props & left a higher pitched pair. ( -there's a long shot!)
These are Merc I/O's yes?
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| Sandy |
Edited by - Sandy on Jul 01 2012 22:23:29 |
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Homeport: The Vineyard
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jtybt15
RO# 3300
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Posted - Jul 01 2012 : 22:23:10
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Check fuel delivery system. Try running on a fresh can of gas.
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Charlie
There is much to be said, in a world like ours, for taking the world as you find it and fishing with a worm.-Bliss Perry, 1904
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Homeport: Ca
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softhds1
RO# 11311
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Posted - Jul 02 2012 : 13:10:00
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replaced both cartridge filters, and replaced both filters in carb. No difference.they were fine 2 weeks ago and this started in middle of cruise. gas is fresh. Filters had a lot of crud in them(carb filters). Dockside the engines will rev fine and 4 barrels will open. Under load I dont the the secondaries are working
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Homeport: NY
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Sandy
RO# 1159
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Posted - Jul 02 2012 : 16:34:32
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"Do you by any chance have an active RPM sync system connected to these engines ?"
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| Sandy |
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Homeport: The Vineyard
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jtybt15
RO# 3300
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Posted - Jul 02 2012 : 16:55:49
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What kind of carbs. Secondaries shouldn't open with no load.
Do the engines run smooth when only going to 3000
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Charlie
There is much to be said, in a world like ours, for taking the world as you find it and fishing with a worm.-Bliss Perry, 1904
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Homeport: Ca
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softhds1
RO# 11311
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Posted - Jul 02 2012 : 17:20:40
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NO RPM SYNC SYSTEM. tHE ENGINES RUN SMOOTH UP TO 3000, but then thats it.
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Homeport: NY
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ernstjrb
RO# 23421
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Posted - Jul 02 2012 : 18:15:02
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I just had the same problem. Turned out the jets were all gunked up with what appeared to be dirt or some kind of grit. Had to have the carbs cleaned out. After cleaning it runs like new.
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| 1994 300 FIESTA VEE "LISA ANN" |
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Homeport: Patsy's Bay Marina, NY
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Billylll
RO# 24494
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Posted - Jul 02 2012 : 20:18:54
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Sounds like in addition to fuel problems it's possible you may be in need of a tune up, meaning wires, plugs and a distributor cap. When is the last time the engines were tuned up?
As far as what happened there is a good chance by letting the fuel run low you sucked the crud off the bottom of the tank into the filters and carbs. Also are the flame arrestors clean? Do you have any backfiring? How old was the fuel you ran on when this happened? Was it Ethanol?
Bill
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WirelessOne,
40 Mainship
Sedan Bridge
Little Egg, N.J. |
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Homeport: Tuckerton, N.J.
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softhds1
RO# 11311
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Posted - Jul 02 2012 : 21:00:55
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Im thinking of the carbs. It was too all of a sudden to be tune up. The filters were gunked up and it was ethanol fuel. It was a 50 50 mix of last years fuel and this years. and the in line filters on the carbs were gunked up. Is there an easy way to clean them without dismantling?
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Homeport: NY
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Billylll
RO# 24494
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Posted - Jul 02 2012 : 22:25:08
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quote:
Originally posted by softhds1
Im thinking of the carbs. It was too all of a sudden to be tune up. The filters were gunked up and it was ethanol fuel. It was a 50 50 mix of last years fuel and this years. and the in line filters on the carbs were gunked up. Is there an easy way to clean them without dismantling?
Properly? Not that I am aware of. However if your tank still has crud (phase seperated Ethanol) in it you might need a pro to empty and clean the tank. I hope it's not that bad. Ethanol is a PIA and depending on the year of the boat can cause major fuel system issues. Please tell me you don't have a fiberglass fuel tank?
Bill
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WirelessOne,
40 Mainship
Sedan Bridge
Little Egg, N.J. |
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Homeport: Tuckerton, N.J.
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jtybt15
RO# 3300
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Posted - Jul 02 2012 : 22:34:51
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I said use a fresh can of gas to by-pass the fuel intake system that may be partially plugged or leaking. A loose or bad connection or crack in the hose or pick-up tube can suck air, reducing the amount of gas.
Listen, we're asking questions and suggesting possible sources or causes of your problem. If you don't systematically answer inquiries and check or do different things to eliminate possible problem areas, we can't check them off as causes. Right now we're looking at the fuel supply system before going to the electrical system.
It's possible you have rubber fuel hoses that aren't rated for alcohol. That can gum up everything from the filters to the carb. You see, there are many possible causes for your problem.
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Charlie
There is much to be said, in a world like ours, for taking the world as you find it and fishing with a worm.-Bliss Perry, 1904
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Homeport: Ca
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Sandy
RO# 1159
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Posted - Jul 02 2012 : 22:39:11
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The carbs may well have some gradoo in them if that stuff had aready made it through a remote filter to an on-engine filter on both engines, but it's seriously long odds the carbs are the primary culprit if both engines suddenly became limited to 3000 rpm at just the same moment in the middle of a cruise. If... they both run on a single tank I'd check the shared A/S valve or pickup before carbs. And I'd recheck a fuel sample from a filter or from tank bottom via the fuel gauge sender hole, for phase separation. Was last year's fuel properly stabilized atleast at the last fill of the season?
Some people have a little luck clearing carb passages by adding Sea Foam or Techron dosing to the fuel in the remote filter cannisters, then running at higher rpm (in the water) so it could clean out quickly and get back to running on just the gas. But I wouldn't expect quite the same results as a true cleaning/ rebuild if the carbs really are a problem. .
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| Sandy |
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Homeport: The Vineyard
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Billylll
RO# 24494
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Posted - Jul 03 2012 : 07:18:55
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quote:
Originally posted by jtybt15
I said use a fresh can of gas to by-pass the fuel intake system that may be partially plugged or leaking. A loose or bad connection or crack in the hose or pick-up tube can suck air, reducing the amount of gas.
Listen, we're asking questions and suggesting possible sources or causes of your problem. If you don't systematically answer inquiries and check or do different things to eliminate possible problem areas, we can't check them off as causes. Right now we're looking at the fuel supply system before going to the electrical system.
It's possible you have rubber fuel hoses that aren't rated for alcohol. That can gum up everything from the filters to the carb. You see, there are many possible causes for your problem.
+1 What Charlie said..........
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WirelessOne,
40 Mainship
Sedan Bridge
Little Egg, N.J. |
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Homeport: Tuckerton, N.J.
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Billylll
RO# 24494
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Posted - Jul 03 2012 : 07:19:00
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quote:
Originally posted by jtybt15
I said use a fresh can of gas to by-pass the fuel intake system that may be partially plugged or leaking. A loose or bad connection or crack in the hose or pick-up tube can suck air, reducing the amount of gas.
Listen, we're asking questions and suggesting possible sources or causes of your problem. If you don't systematically answer inquiries and check or do different things to eliminate possible problem areas, we can't check them off as causes. Right now we're looking at the fuel supply system before going to the electrical system.
It's possible you have rubber fuel hoses that aren't rated for alcohol. That can gum up everything from the filters to the carb. You see, there are many possible causes for your problem.
+1 What Charlie said..........
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WirelessOne,
40 Mainship
Sedan Bridge
Little Egg, N.J. |
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Homeport: Tuckerton, N.J.
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softhds1
RO# 11311
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Posted - Jul 04 2012 : 09:07:05
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is it possible to have a clogged fuel tank pickup? It would somewhere where there is a common system is where it has toi be to effect both engines in same way at same time. What do u guys think?
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Homeport: NY
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JimPend
RO# 5022
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Posted - Jul 04 2012 : 09:38:15
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We had this happen to several boats in our Marina turned out to be timing advance was rusted out on one engine. One engine not running up will slow the other one too.
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| Jim P. |
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Homeport: Port Clinton, OH
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Sandy
RO# 1159
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Posted - Jul 04 2012 : 12:13:32
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Another somewhat long shot for the list:
Restricted exhaust (errant flapper?) is another potential cause of limited revs under load. Any change in exhaust sound note noticed?
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| Sandy |
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Homeport: The Vineyard
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softhds1
RO# 11311
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Posted - Jul 06 2012 : 16:28:17
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Replaced both coils(oil leaking. Tomorrow going to change check valve and blow out tube)
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Homeport: NY
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| BoaterEd |
© 2010 BoaterEd, Inc. |
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twin 305's wont rev
