Loss of RPM

[kwoolard]

Boat: 1999 235WA Sea Pro
Engine: 5.7L Alpha Gen II
Eng. Ser. No.: 0L364401

I have another thread out there trying to find the right rebuild kit for my carb, but I wanted to ask in this thread if anyone could tell me the reason for my loss of rpm after the boat sat up for the winter.

Since the boats last outing in October of last year, I have:

1: Installed a fresh water cooling kit (which works great by the way!)
2: Installed a tune up kit (plugs, cap, rotor, coil).
3: Adjusted my initial timing in base mode from 25 degrees to 10 degrees (this solved my pinging problem, thanks Don and everyone else)
4: I didn't fill the boat up with gas before setting it up for the winter but I did add some fuel stabilizer to a half full tank.
5: Changed the fuel water seperator which had about 3-4 ounces of water in it after my initial run this year.(condensation in the tank over the winter?)

Before these changes, my WOT last year was 4500 rpms.

My symptoms are somewhat of a rough idle, very rough/vibration in engine while accelerating up until about 2200 rpm, then it smooths out right much. WOT now of only 3000-3200 rpm. After a short run at WOT, I cut the engine off and took the flame aresstor off and noticed fuel dumping from the cluster. I tapped on the carburetor thinking that it was a stuck float, and cranked back up and the engine idled the best it has in a while and there was not any more rich exhaust smell. However, my WOT was still at 3000-3200. I decided to just cruise at that speed for a couple of miles and noticed every now and then the engine would pick up a 100-200 rpms without me touching the throttle, it finally maxed out 4000 rpms. I anchored up for a while, and then started to head back to the dock and when I would push the throttle from idle to start to plane the engines rpms would drop to nothing and the engine would cut off. Finally got the engine to plane without choking off and my WOT rpms went back to 3200.

I have the carburetor off now for a rebuild, whether that is the problem or not, I feel it is time for one. Is there anything else I should be checking for this sudden loss of power/rpm?

Thanks.

 

[Don S]

Re: Loss of RPM

IF you had that much water in the filter before, I would bet it's now full of water again. What you really need to do is pull the filter again and see if there is water in it again, if there is, you will need to pump the water out of the tank. It's an easy enough job.
head to NAPA and get a cheap electric fuel pump. Make and model doesn't make any difference. Pickup some fittings for the pump so you can attach some 1/4" ID clear tubing to both ends of the pump. Then get you a couple of feet of copper tubing that will fit tight inside the clear tubing, and put it on the pickup side of the pump. Make the output hose long enough to go into a container for your junk gas.
Now, put some wires on the pump (a red and black will work..... red for positive and black for negative) put some clips on the end so you can hook to a battery.
NOW, since water always settles to the bottom of the tank, raise the bow of the boat so the back of the tank is lower than the front. The water will also head to the back.
Then remove the fuel pickup tube from the tank (make sure the fuel level is low enough when you start that it doesn't run out of the fitting when you pull it out).
Start your electric fuel pump and stick the copper tube all the way to the bottom, move it around and you will get all the water and leave the gas.

Dispose of the contaminated fuel properly

 

[kwoolard]

Re: Loss of RPM

Thanks Don, I am hoping that it is just water in the tank. Regardless, I think it was definitely time for a carb rebuild. I took the carb apart last night and noticed that the bottom of the bowl was covered with this brown/brick red varnish. Also noticed that a couple of pin size holes were plugged up with that stuff. Hopefully, the carb rebuild and the draining of the tank will eliminate my problem.

I dumped the contents of the fuel bowl into a container and saw a small water droplet about the size of a BB floating at the bottom, so there was a little water still making it to the carb after replacement of the fuel/water separator. Tonight I am going to remove the water separator and see how much more water was collected.

Question: In the past I have soaked carburetor bodies overnight in Chemtool carb cleaner, after removing the plastic bushings and shaft seals of course. However, reading in the manual last night it states not to remove the throttle plates or shaft because the body and shaft are a complete assembly, yet it states that I can soak the parts in carb cleaner for no longer that 2 hours. Will this carb cleaner destroy the shaft seals in the throttle shaft?

 

[kwoolard]

Re: Loss of RPM

I have rebuilt my carburetor and have got everything back together except for the choke coil. I am just trying to figure out how the choke system operates.

I know that on carbed engines you have to push the throttle to WOT which sets the choke in its nearly closed position and then as choke coil warms up it opens the choke plate to full open. However, looking at the way the choke spring is wound it seems as if when the choke coil is heated up with the supplied voltage that the coil will unwind. If the coil unwinds then it seems it will close the choke plate instead of open it. My question is: does the choke coil unwind or wind up when it is heated? If it winds up then I can see that when the engine is running, the incoming air through the carb will force the choke plate open, and will ride with the winding coil. Then as the coil cools, it pulls the choke plate back to the nearly closed position or just keeps pressure on it until the throttle is push WOT and allows the choke plate to close.

 

[kwoolard]

Re: Loss of RPM

The carburetor rebuild helped out with my rough idling, but I still had some intermittent loss of rpm. It seemed as if it was electrical since I could be cruising along at 3000 rpms and the ignition would just die. Restarting would be easy sometimes and then sometimes I would get a backfire through the carb, as if the timing was jumping around.

I then took the connections off of the ignition module and noticed when I unplugged them water came seeping out of the plugs. How water got in there I don't have a clue, unless it was condensation. I do know that the previous owner of the boat pressure washed the engine while cleaning the boat, so maybe he forced some water in the plugs. Either way, the terminals had a blue/green corrosion on them. I cleaned them off with a toothbrush and my wife's fingernail file, and viola, problem solved. The engine runs smooth, accelerates consistently and no more ignition cut out.

The question is, should I replace the plug connectors into the ignition module and replace the modules, since the corrosion could be deeper than the eye can see? If so, where can I get the plugs from?

Thanks,
Keith

 

[kwoolard]

Re: Loss of RPM

Or could I just clean the contacts with WD-40?

I have read that DonS recommended putting dielectric grease on the connectors, if I put the grease on the pins before mating with the plugs wouldn't this prevent a good contact between the pins and the plug? Dielectric grease is nonconductive right?

 

[Maclin]

Re: Loss of RPM

I would not worryy about it too much. If the connectors are still "tight" and have an interference fit then they should squeege out any grease as they make metal to metal contact.

 

[kwoolard]

Re: Loss of RPM

My boat weighs about 5200 lbs with engine/outdrive and full tank of gas (125gal). My performance with 2 people on board and a half tank of gas was about 4500rpms @ 40mph. Sunday when I took the boat out for a test run to verify that it was the connectors acting up, the performance with 5 people on board and a full tank of gas was 4100 rpms @ 35 mph. Is this extra weight slowing me down that much, and if so should I drop a pitch in prop?

Could it be that I have shorted my ICM out when water was in the connectors and it is preventing me from gaining full performance from my engine?

I would think a 250 HP engine should be able to push this boat pretty good.

 

[FreeBeeTony]

Re: Loss of RPM

What size prop are you turning? My boat weighs ~4000# w/o gas or passengers and I cruise at ~25MPH @ 3500RPM, I'm turning a 4 blade 15X16 prop. WOT ~ 4800RPM by myself.........not sure of speed at WOT.

 

[kwoolard]

Re: Loss of RPM

Tony, what size and type of boat?

I am currently running an aluminum 15-1/4 x 15 three blade prop. I can get the numbers on the prop and post tonight. Do you think I could go with a different prop configuration....vented, 4-blade, cupped, etc.?

 

[FreeBeeTony]

Re: Loss of RPM

My boat is a 24' Grady White Offshore............I am by no means able to give you any advice on props/configuration.........I was just giving you my numbers for comparrison purposes.............if you're getting 40MPH in that heavy of a boat and your WOT is OK I think your set-up is pretty good........in my opinion anyway!