thefishingfreak
Seaman Apprentice
- Joined
- May 12, 2002
- Messages
- 46
Hi- I appreciate your time in advance for reading this and any help you might be able to offer. Sorry its long, but I figured I would give you ALL the info as I'm not sure what is pertinent and what is coincidental.<br /> <br />You seem to have some experience with the Yams. My 1995 250 carb is surging in the main power band, started off and is getting worse. Found that my high speed electric diaphram pump gasket was leaking. My friend took it off and rebuilt it. You can hear it run when the key is in the on position, but it never shuts off (as if it builds pressure up). However, I'm still having the problem. Funny thing is that it is somewhat intermittant in that it feels like you are putting out about 50 less horses when you punch it and she won't quite get full RPM. However, the surging isn't always evident. Yet when it starts you need to keep advancing the throttle and really open it up to get it to stop.<br /> <br />New fuel pump (the one that was rebuilt) is $205 bucks and I hate to replace it if its not the problem. Those three gold pumps on the side I never thought of. <br /> <br />Thanks for your time- shops are up to $130/hr for labor around here so its the last place I want to go unless absolutely necessary.<br /> <br />Take care<br />Rob- Long Island, NY<br /> <br />SORRY ABOUT THE LENGTH BUT FOR MORE SPECIFICS READ ON:<br /> <br /><br />SYMPTOMS:<br />Always starts<br />Never stalls<br />Never stops running<br />Slow speed- below plane doesn't seem to be a problem<br />Once on plane and throttle set, engine will begin to surge (rpm goes down and then back up) and/or also just drop rpm. I try to combat this by opening the throttle further and it somewhat works and near WOT it stops surging but you are not getting 100% out of her. <br /><br />I'm sure many things could cause this, but can some things be ruled out, like:<br />Powerpacks<br />Stator<br />Coils<br />Computer<br />Carbs <br /><br />Since the middle of last August, I have not been able to figure out what is causing my grief. Here are some of the background facts, but I have no way of knowing if they are coincidental, ancillary, or a cause. <br /><br />1. Around this time period, Ethanol is in marine fuel and causing boaters 'grief'. <br /><br />2. Season before last, the boat would only wax and wane between 3400 and 3500. If throttle set lower or higher, it did not waver. Plenty of power. <br /><br />2. I was horsing around the day 'my trouble started' and when moving slowly at trolling speed, I goosed the throttle hard (WOT for a second) and then quickly pulled it back. Five minutes later when I came up to cruising speed, something was amiss, like I was down a cylinder. I figured that I had fouled a plug. I changed plugs and she seem to be back up to health. <br /><br />4. Next time out the boat started surging at a wider range than 3400-3500. Like 3400-3800 rpm. I thought I had bad fuel. Changed water separator, started back up and seemed to be ok. Checked compression- solid). <br /><br />5. Problem starting again- I went through another set of plugs, two more water separators, ran the tank just about dry (10 gallons in reserve), put many cans of that water absorb and other products over those two tanks. <br /><br />6. Found that my gasket on the diaphram central fuel pump was leaking fuel. Had it rebuilt. Took it out for test drive this March- ran pretty well. Even got another 100 rpm on top end. Took about again last week- problem back. WOT down to 4700. Acceleration weaker. Like you've lost 75 horses. Although stopping the boat does not seem to be a variable, the problem is quasi intermittant in that I can stop, start again and sometimes get it back to normal WOT RPM. Yet even then the cadence is just not as harmonic as it once was (could just be my imagination).<br /><br /> <br />NOW THE EVEN LONGER VERSION-<br /> <br />In an effort to solve the Yamaha's (1995 250 carb) surging problem, I hooked up an external tank with new primer bulb and took it for a spin. At first, she seemed to be pretty happy and up to par, switched back over to main tank and didn't notice too much difference- still running ok. Decided to ride around a bit and then it starting acting up again. As I quickly came off plane, I noticed all this water running out the hole that the cables, etc enter the cowling area. <br /><br />I took cover off and could see some water laying in there. I proceeded to bring it on plane and she seemed down power again and sounded like I wasn't getting all cylinders to come on line correctly. <br /><br />As an aside, my left lower spark plug gets rusty on the outside all the time. When you pull the plugs they are all similar in appearance and the last time I checked compression it was good- last Fall. <br /><br />I'm wondering if I've a leak/crack in the cooling system which is spraying the engine down under power and shorting it out (going to ground). When it is idling you can not see water come out of any place, which might explain why it idles and trolls ok (i.e. the water isn't spraying all over the place at that point. I was alone so I couldn't easily run it at high speed and look around the engine compartment with the cover off. <br /><br />NEXT- I ran the engine on the hose today and looked around for water leaking. Idled it for about ten minutes and found no water. Brought it up to 1500rpm for about two minutes and kept checking. Everything was bone dry. Granted it might not be the same as 4500 with the backpressure of pushing a boat. <br /><br />I checked some of the hoses that appear to run water and they were not leaking at all. My cover does rock slightly from side to side about 1/8inch (about a 95% tight fit), but I don't think much water from the outside would be getting in there from the outside spray. <br /><br />The drain holes from the inside appear to drain into the shaft area and you can not inspect them from the outside. I didn't think to run anything down them to clean them out (next time).
<br /><br />rodbolt, you rock!