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+--- Thread: RPM issue on 2700 Tiara (/showthread.php?tid=268)
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RPM issue on 2700 Tiara - Wish You Were Here - 11-05-2012
Hi, I have a 1985 2700 Tiara Pursuit that I purchased in Jan 2012. The boat is still in great condition and the records of all the mantainence are there. When I first bought the boat, I brought it down from Redondo Beach to Dana Point, CA about a 60 mile trek. I noticed that one of the engines sounded like the it was reving ever so slightly off...meaning it sounded like it bogged a bit here an dthere randomly.
As time went on and I use the boat on average once a week, it became apparent that it was the starboard engine that had the issues.
The engines are Crusader 270's and when the boat gets out of the harbor, it runs perfectly for about 5 miles then the starboard engine starts to bog...meaning that at optimal fuel efficiency, it should run at 2900 RPM's and get about 10 GPH per engine. The port side runs perfect however, after about 5 miles out, the starboard's RPM's drops down to about 2000 ~ 2200 RPM's and if I throw the throttle wide open, it may jump up a bit then come down again...can't get it to stay at the right RPM's for any distance and I get even less GPH...I may get 16 ~ 18 GPH on my starboard at this point and still only get 2000 RPM's. It destroys any range I may have had on the boat not to mention the cost of the gas!
So, we've gone through a couple of months of going through a process of elimination...
1. Emptied the fuel and put fresh fuel in
2. Cleaned and re-cleaned the carburator
3. Changed out the electric coils - thinking this may be an electrical issue
And thus far, nothing has worked.
Does anyone here have any experience w/ something such as this? Can anyone shed some light on what else it may be?
Any help would be appreciated!
RPM issue on 2700 Tiara - Uhehner - 11-05-2012
My first guess without listening to the engines is that it is starving for fuel. I would change the primary fuel filter and the small fuel filter in the carburator. Then I would look at the fuel tank vent or maybe leave the gas cap loose. After that you need a good Crusader Tech that can determine if you are loosing a cylinder. How old are the wires and plugs? What does the temperature gauge read?
Capt. George
RPM issue on 2700 Tiara - Wish You Were Here - 11-05-2012
Capt George, thanks for the reply. The engine sounds great till you get it running for a while...even at idle or troll speed, it runs and sounds fine. Plugs are new and we just did a service and oil change. Mechanic went through the wires and they look fine too. At the service, we changed the fuel filters both of them...actaully he said there are three of them.
Interesting thing that you say I may be loosing a cylinder...how do you identify that? Would it run w/ all cylinders only to have one crap out once engine is warmed up?
Temps run fine at about 160~180 degrees.
Question - if it is starving for fuel, would it still burn that much gas? Meaning it would suck gas as if it were going 3000 RPM when it is actaully only going 2000 RPM's?
RPM issue on 2700 Tiara - Uhehner - 11-06-2012
Wires may look fine but still break down under high voltage. The best easy check is to run the engine at night with all lights off. If you have any arc over it's easy to spot. Another thought is --- is your tach giving you false readings? How are you measuring the fuel consumption, with a flow gauge? Can you sync the engines by ear? Can you hear one slow down? A good tech with an engine analyzer can quickly isolate your problems. Capt. George
RPM issue on 2700 Tiara - Wish You Were Here - 11-06-2012
Capt George,
what do you mean by arc over?
Also, I do have a flow guage. I don't think the tach is giving me false readings since the meter shows steady readings out of the start and then the tach starts to read lower RPM's and I can hear the one engine slow down and then my speedometer also shows slowing of actual speed. However, my fuel consumption stays as if the engine was running at original higher RPM...
RPM issue on 2700 Tiara - Uhehner - 11-07-2012
An arc over is when the high volage destined for the spark plug jumps out of the wire to ground. You will see orange or bright blue sparks. A sure sign of leaking wires. When a cylinder miss fires it still takes in a fuel charge and expels it on the next stroke. Start looking for a good marine engine man with more than just a screw driver and pliers. I'm talking about an ignition analyzer, timing light, compression gauge and the knowledge to use them. Capt. George
RPM issue on 2700 Tiara - Wish You Were Here - 11-07-2012
Thanks for the insight...Hopefully there is one around Dana Point CA!
RPM issue on 2700 Tiara - Uhehner - 11-09-2012
After rereading your inputs I would put my money on a weak spark. As the temperature rises and the RPMs increase you need more voltage at the plug for it to fire. This could be wires, plugs, coil, distributor cap or your electronic ignition module if you have one. If you don't then its a Points and Condensor issue. If you have a P&C distributor I would convert it to electronic ignition. Makes all the difference in the world. I'm talking from experience. Ask any guy with an old high performance Corvette. It's not an expensive changeover. Capt. George
RPM issue on 2700 Tiara - Wish You Were Here - 11-09-2012
Capt George,
Thanks again! I believe my mechanic isolated the issue...so, port was running fine. Changed out the carbs and RPM issue remained on starboard side. But the fuel consumption dropped on starboard and port went up high on fuel consumption.
Then he switched the distributors around and now starboard is running perfect! Port side is now having similar exact same issues as the starboard did previously...so we believe it is the distributor module for the RPM's issue.
So, next step is to get a new distributor module and a new carburator and hopefully I'm back in business!
does that sound right to you?
You've been a great help so your input is vaulable!
RPM issue on 2700 Tiara - Uhehner - 11-09-2012
I still don't understand the fuel consumption and carburator issue yet but get the engine running correctly first. I would purchase a new distributor module. This was my guess on 11/9. Next, be sure to set the timing correctly using a timing light. If you set it too low, your mileage goes down. If you set it too high ( degrees before TDC ) you will burn up a piston. Time both engines. Capt. George