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Topic Title: Limited RPM's on one engine.
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Created On: 09/04/2007 01:49:22 PM
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 09/04/2007 01:49:22 PM
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TheJudge
Admiral

Posts: 282
Joined: 05/01/2006

Before I go chasing down every conceiveable possibility I thought I would throw my problem before the experts. I have twin 1984 Crusader 270's with four barrel carbs. I have previously converted to factory aftermarket electronic ignitions from Crusader. Everything has run great for over a year. Now recently I discovered that when I power up that my port engine is limited in rpm's to 2800 while the starboard will go to 3800+. This 2800 on both engines will result in about 16mph running against the current. This boat has always been capable of running 30mph if it had to though my pocketbook does not allow much of this. It is not that I need all those rpms but still I do not want an engine that is not in prime running condition. My first thought was the throttle cable had stretched and I was not getting the carb opened up. But I checked this when I came in and it is pulling the linkage all the way when the throttle lever is jammed forward. So now I have to look elsewhere when next I visit the boat. Several avenues come to mind such as somehow the ignition has jumped time, but it seems to run too smooth at 2800 for that. Still, I can put a timing light on it easily. Next I thought about the fuel pump might not be performing up to specs and it was not getting enough fuel when opened up. Finally I thought about the carburator itself though I had these rebuilt two years ago and they have performed flawlessly. So I am open to suggestions as I will not see the boat for about three weeks.

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The Judge Rules
 09/04/2007 07:07:51 PM
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Tonka
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Did you make sure the secondaries on that carb are opening up, Judge?

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1975 42' Gibson Standard
Lake Cumberland, Kentucky
 09/05/2007 05:34:22 AM
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alreadygone
Admiral

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Have had exactly the same problem in the past when fuel filter was restricted. Simplest, quickest,cheapest,first thing to check of cars and boats. Subjected to trash and condensation in both applications, yet everyone goes looking for something complicated and expensive first.

Bob

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I carry a gun because it's too tiring carrying a cop.
 09/05/2007 09:46:21 AM
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TheJudge
Admiral

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Another friend has suggested the fuel separators and inline fuel filter as a possibility. I did not replace those this season for the first time because I have run the boat very little in the past year. Penny wise and pound foolish as they say. It certainly is worth looking into when I get back up there. I have also been told that if that side of the boat gets the afternoon sun, which it does, that this red hot summer could have produced excessive plant growth on the prop and shaft on that side. Sounds like I might also be taking a dip though I think I will anchor out for that. I do not trust what might be in the water at the dock. Too many people never seem to move their boats though they are here every weekend.

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The Judge Rules
 09/05/2007 01:27:31 PM
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Coolbreeze
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Judge,
Does the timing light you are going to use have an inductive pickup, so you just clip it around the plug wire??

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Rick
1994 Sumerset 80'
Lake Lanier, Ga.
 09/05/2007 07:34:22 PM
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alreadygone
Admiral

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If you have spin-on filters,,it's really interesting to pour contents out into a clear, or light colored container to see what's actually in there!

Bob

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I carry a gun because it's too tiring carrying a cop.
 09/14/2007 08:01:22 PM
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enginetamer
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Hi Judge, can you rule out a gradual build-up of growths on propellers and hull?

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lookin' for adventure and the next wild engine!
 09/17/2007 09:35:38 AM
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TheJudge
Admiral

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I will not be back on the boat until the 22nd to try any of these fixes. We spent this weekend in Goose Pond Colony Marina near Scottsboro, AL helping our friends pack up all the stuff they carried on the Great Loop.

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The Judge Rules
 09/26/2007 03:19:10 PM
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TheJudge
Admiral

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As a followup to this topic I went to the boat this weekend. Changed water separator filters and fuel filters and there was no water but a bit of trash in portside water separator which could have affected pickup of fuel. Took the boat out and had basically the same problen with port engine topping out at 2800rpm and now the starboard was topping out at 3200rpm. I immediatly became highly suspicious of growth on the bottom and especially the props. This seemed to be confirmed when after a bit of hard running the port picked up to 2900rpm's still going upstream. On the downstream run it went to 3000. When I returned to the marina I took a cursory look from the dock and my hull is truly slimed up and the props are worse. Looks like I need to put on a mask and do some diving. This is what happens when the price of fuel makes you sit at the dock most of the time. I now have a 16' runabout in dry storage at the marina so we are going out on the water more but this does not help keep the bottom of the big boat clean. Amazing how much drag a little growth puts on a prop.

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The Judge Rules
 09/26/2007 04:20:10 PM
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Dave
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Actually Judge, running the boat will help keep the bottom clean. My boats were always very busy and I seldom had to clean the bottoms, only the waterline. My neighbors "dock" boats on the otherhand, needed monthly cleaning. Same with the props.
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