Can't get above 2500 RPM

[code90]

I have a 1992 125hp. The boat sat on trailer for 18 months and of course wouldn't start. I cleaned the first carb and aside from the old fuel, it looked clean. Put it back together (with old parts) and drained old fuel from other three. I emptied the old gas from the tank and the motor fired right up with fresh fuel. It ran great for about 20 minutes, then powered down to about 2500 RPM and would not go higher. No alarm sounded. Still put out water from pee hole. I figured the motor went into SLOW mode and had overheated. It would idle back to the dock. After sitting for an hour, it would run again and did fine until 20 minutes of WOT then it powered down to 2500 RPM again. Next replaced the impeller. Making good stream through pee hole (not dramatically more). Still having problems.<br />On next trip out, started, idled well. But when tried to open up throttle, the motor kicked, sputtered and appeared ready to jump off the transom (did not quit running though). Would run under 2500RPM without problem. I then replaced the fuel lines and bulb. On next trip out, no more kicking or sputtering, but will not go above 2500 RPM at all. Acts the same way as when I thought it had overheated, but does so from the time it is started. It will now start and idle well. It will not power up past 2500 RPM at all. <br />Reviewed manual. Still looking for suggestions. Hope all the history helps instead of hurts. Thanks.

 

[fireman57]

Re: Can't get above 2500 RPM

First let me welcome you to iboats. When it goes into "slow Mode" Do a spark check. you could be dropping a cylinder(s).

 

[code90]

Re: Can't get above 2500 RPM

Thanks for the suggestion. I'll try it tomorrow on the day off.

 

[code90]

Re: Can't get above 2500 RPM

If spark check seems OK, where do I go from there?

 

[Goodoleboy]

Re: Can't get above 2500 RPM

If it were me I would take carbs apart and replace needle and seats check float levels.<br /><br />Clean all passages, Remove welch plugs, soak with carb cleaner, use compressed air to clear.<br /><br />Good luck!

 

[Cricket Too]

Re: Can't get above 2500 RPM

Well you could check and make sure your temp sensor isn't malfunctioning and putting your engine into SLOW when it's not really overheating. Or you may not be going into SLOW at all, I would tear those carbs down and clean them good and rebuild with new kits. If they sat for a year and a half with fuel in them, it's a pretty safe bet that they are varnished up.

 

[Cricket Too]

Re: Can't get above 2500 RPM

Goodoleboy got to it first, definitely rebuild carbs.

 

[code90]

Re: Can't get above 2500 RPM

I'll let you know how it goes, thanks.

 

[TBarCYa]

Re: Can't get above 2500 RPM

What is this "SLOW" mode and how do I know if my engine is in it?? I didn't find anything about it in the Clymer manual.

 

[code90]

Re: Can't get above 2500 RPM

SLOW mode is a self protecting feature. When the motor overheats, you are forced to go at a slow RPM. It's in Clymer in the troubleshooting section. <br /><br />I confirmed that the overheating horn is working in the boat (tan wire to block). When running I do not get the horn. If I do not hear a horn, could I be in SLOW mode? <br /><br />I seem to be getting spark to all cylinders when tied to the dock. Haven't figured out how to check spark while running.<br /><br /> Going to try to pick up carb kits this afternoon.

 

[code90]

Re: Can't get above 2500 RPM

Carb kits are all done. Put in new plugs. Idles well. With the muffs on at the house, I can rev up the motor well. When I put it in the water and try to run up to speed, it now sputters, kicks (misses?) and looks like the motor is going to jump off the boat at about 2000RPM and will not go faster. <br /><br />Any thoughts?

 

[Seasport]

Re: Can't get above 2500 RPM

Sounds like the Powerpack is putting your motor into SLOW mode. This can happen even if the motor is not overheating and can be caused by a few things.<br /><br />I'm more familar with later motors but I presume it will be similar for yours. Check:<br /><br />(i) Faulty temperature switch.<br />Check out the temperature switches on each cylinder head (should be tan/blue wire). These connect to ground when the engine overheats. You can disconnect the wire to disarm the switches.<br />However, you should get a warning signal also if this is the problem - so may be not.<br /><br />(ii) Check out the blocking diode in the engine harness (tan wire). Apparently, if this is faulty the powerpack can go into SLOW mode with no warning lights coming on. You can test the diode by doing a conductivity test one way and then reverse the meter leads. It should only conduct in one direction.<br /><br />(iii) Powerpack could be faulty<br /><br />I've also heard that if the temp. sensor wires are run too close to the plug leads this can cause the powerpack to activate SLOW mode.

 

[code90]

Re: Can't get above 2500 RPM

Seasport, I think you are coming from the right direction. <br /><br />I have checked the overheating warning horn by connecting the tan temperature switch wire to the block. It sounds when shorted to block. That makes me suspicious that temp switches are ok. I'll pull them the next chance I get. Or could try to run boat with them disconnected to see if problem solved.<br /><br />I tried following Clymer to test the diode. I'm not sure I tested it correctly. I'll review that again.<br /><br />Is there any way to check the powerpack (short of replacing it?)<br /><br />Can just SLOW mode itself cause the motor to miss sputter, and kick?

 

[Seasport]

Re: Can't get above 2500 RPM

To check the diode you need to disconnect it from the circuit (unplug the wiring harness), set your meter to measure resistance (ohms) then connect the meter across the diode (at each end of the cable containing the diode) one way - note the reading (if any) and then reverse the meter leads and read again. You should get a reading (low ohms) in one direction and no reading in the other (infinite ohms).<br /><br />Your motor will definitely kick & shudder when it is in SLOW mode.<br /><br />Unfortunately, I don't think there is any way to test the Powerpack. SLOW is an internal function. Another member recently reported a similar problem to yours and it turned out to be the Powerpack. It would be good if you could try another one before buying though - just in case it's not the problem. Have any friends with the same motor? Or maybe a friendly dealer would let you try one.

 

[code90]

Re: Can't get above 2500 RPM

Thanks for all the advice. I'll try some more with the motor on monday (next day off)

 

[code90]

Re: Can't get above 2500 RPM

I finally got a real spark tester. My homemade version gave me fits. I found no spark on #3. Switched coil from 3 to 1 and then had no spark on 1 (with spark now present in 3). Great! I replaced the coil and went for test ride. <br /><br />Ran great for the 20 min test run. No problems anywhere. THEN... took wife out in boat the next day. Boat returned to old tricks. Starts great, ran up to WOT for 200yards then started to kick, miss, and forced me back down to 2000 rpm. Haven't rechecked spark (boat still in water). Waiting for another day off.<br /><br />I know I'm no mecanical genius, but now wife is sure of it. Any thoughts of where to look now?

 

[Goodoleboy]

Re: Can't get above 2500 RPM

I would guess you have one or more coils or mabey power pack also that is breaking down when heated up.<br />You can while on the muffs take a hair dryier and speed up heat process and see if spark goes away on one or my cylinders.<br /><br />As for you wife,s lack of confindence in your mach. abilities. Your sorta on your own their. <br /><br />But mabey while shes asleep sneak out of the house and pull all but a couple or three plug wires on her car.<br /><br />Then when she comes in the house and says honey my car sounds funny. You can non shauantly walk out with her and have her tun it over while you look on with an interested look on your face.<br /><br />Ok..Ok...Honey Just uh sec. put the plug wires back on. vroooommmmmmm!<br /><br />WOW....WOW ....You really are a machanic! Where did you learn how to do that.<br /><br />Ah..you know honey...Guys with boats know stuff!<br /><br />Grin!<br /><br />Good Luck!

 

[Seasport]

Re: Can't get above 2500 RPM

It does sound like the powerpack is playing up when it heats up. As Goodoleboy says, get a hairdryer/hot air gun and heat up the powerpack to see if you can cause the problem when you're on the muffs. May be able to pin it down this way. As I said earlier another iboats member reported a very similar problem a month or so back and it turned out to be the powerpack.

 

[code90]

Re: Can't get above 2500 RPM

Here's a follow up post. I didn't want to invest the $200 to try out a power pack (since I couldn't return the electrical part if that didn't fix the problem). I finally put the motor in the shop. Of course, they replaced the power pack and everything is working great. Thanks for all the help here.