OK, i just finished replacing my badly chopped up water pump/impeller which fixed the overheat alarm (http://texasfishingforum.com/forums/ubbthreads.php/topics/2611167/78_evinrude_flooding_problem)... then we took the boat out yesterday, got her on the water and tried to bore it out, but top speed was only about 10mph, the engine sounded fine and i tried pushing the throttle down all the way (the front of the boat trimmed up just fine) and tried adjusting the trim up and down to gain speed, but nothing.... just trickled along around the lake at no more than 10mph with the tip of the boat up in the air.... what could be wrong?

Prop is part of it, but not all of it...Could be your throttle cable could be off it's setting...The engine's timing could be off...

I can come by tomorrow and look at it with you, if you want...I can't check the timing, but I can check the rest of it...PM and let me know...

It will do that if you have lost spark in one hole or a carb is either plugged up or has water in it, or the fuel pump has taken a dump. Since the engine has been hot a couple of times, and you're probably running Champion plugs, Check the plugs or change them out. Champions tend (IMHO) to break down when exposed to extream temp.

bigtex, are you sure you have the right plugs?

If you didn't get the shop manual yet, pm me and I'll tell you which ones it says to use, but just a thought, my motor is suppose to have champions in it, but lonestarson's mechanic said to use NGK instead.

Good luck, hopefully we'll get both our motors runnin soon

In the process of disconnecting and connecting the shift shaft you may have: disconnected linkage to bottom carb by accident. Have had several of the early controls that where the warm-up lever pivots, the screw and bushing wears not allowing full throttle. You can tell if the warm-up lever has a lot of play. You can also remove the air box, full throttle control and look at carb butterflys to see if both are going horizontal. Good Luck

well, the hoses are fine; the spark plugs i replaced a few days ago (after water pump install) and they look fine, too; gary, i checked in the area where we had so much trouble pulling the shift rod screw and there was nothing we disconnected or anything like that...

i flipped thru the manual and there is a part about a "S.L.O.W. mode" which activates once the engine is overheated and limits speed to [get this] no more than 2,000 RPM's. doesn't this translate into about 10 miles per hour???? we know for a fact that the engine did over heat when the alarm went off, but now that problem is fixed because we changed the water pump, the water cycles thru the engine just fine which cools it off, and there is no more overheat alarm.

i think that "S.L.O.W. mode" is limiting the engine to 2,000 RPM's; this makes perfect sense, because when we took it out on the water the engine sounded fine and all that, but it never got beyond about 10mph which sounds theoretically close to the 2,000 RPM limit put on by "S.L.O.W. mode". anyways, the manual says to disconnect the overheat sensor wire (a tan wire, which i think i have found) to make sure it works. maybe this sensor simply has to be "re-set" (unplugged, plugged) in order to "tell" the engine that there is no more overheating and to quit limiting the speed to 2,000 RPM's... anyone heard of this mode before??????

from the manual, ch.3 troubleshooting, "S.L.O.W. Operation and Testing".........

"the S.L.O.W. (speed limiting overheat warning) circuit is activated when the engine temperature exceeds 203 degrees F. when activated, the S.L.O.W. mode will limit the engine speed to approximately 2,000 RPM. to be deactivated, the engine must be cooled to 162 degrees F and the engine speed must be slowed to an idle. on models equipped with remote electric start, a blocking diode located in the engine wiring harness is used to isolate the S.L.O.W. warning system from other warning horn signals......"

Open the air box in the front and look at the butterflies at wide open throttle. ( engine off). They should be horizontal.

If I remember right this is an older model and it wo`nt have the Guardian or SLOW system. You might want to look at the ignition wiring real close. When a motor gets that hot it can melt the insulation causing wires to go to ground where they come close to the block and cylinder heads. If all else fails, start over. Good Luck

do you have a spark checker if not get one from autozone only $3.00 check spark on each cylinder also they will loan you a
compression tester this will help people here tell you whats
wrong

Since this engine has been overheated I would for sure do a compression test before I started taking things apart... It is easy to do... If you have good compression on all four you can start looking for something else.. How long has it been since the carbs have been rebuilt???? Dirty carbs can make one hard to start and run bad... A lean condition on a carb can cause a piston to burn... You could also have an electrical problem... You might consider going to www.bassboatcentral.com and posting your problem on the john/rude board...Just remember to post your serial # and model # and explain your problem from the time it started and what you have done so far...Do the compression test first... Good luck and hope you get it going....

BigTexNick...I talked to my mechanic today about your engine and told him what you have posted here...He said you can run a compression test, but it might not tell you anything concrete...According to him, from what you've posted, you've more than likely blown the vacuum ring on one of the cylinders...Unless you've blown a compression ring (which are the first rings on the piston near the sparkplugs), a compression test won't reveal the issue...

If in fact you've blown the vacuum ring on a piston, you'll need to open up the block and change them out...Otherwise, you'll blow the whole powerhead...

Outboard engines don't take a lot of heat to blow those rings...

Referring to your original thread :

When you originally heard the overtemp warning born, you said you took it back to the ramp and shut it down. Did you shut it down and let it cool off first, or did you just run it back to the ramp ?

Another question. You mentioned the previous owner saying "it was just flooded." I find that odd.

Is there a possibility that he sold you the rig without disclosing a semi- stuck ring or piston? Like maybe it had partially seized once and he quickly sold the boat ?

Third question: Had it EVER run well since you've owned it or test drove it ?

I certainly hope you only have a fuel or prop problem...and not a nearly seized up powerhead.

oldfrog, when i originally heard the alarm, i was in the middle of a small lake (few hundred yards wide) and turned right around and went back to the ramp and then shut it off....

i honestly do not know what the seller did to this boat. the seller told me nothing was wrong with the engine, it ran (his words) "like a champ". he seemed surprised that i'm having all these problems. i suspect he was having trouble with it and sold me the boat knowing it had these issues, but without disclosing ANYTHING!... yes, the seller told me he "thought" the alarm meant the engine was flooded. of course, i researched that problem (and consulted you guys) who correctly informed me that the alarm was overheating, so i replaced the water pump and the alarm no longer sounds.... it really ticks me off that he sold me a boat with a badly torn up impeller, an overheat alarm, and now this speed limiting issue---all while telling me it never had any problems and "ran like a champ." i'm getting very close to demanding a refund and, if rejected, taking him to court.

third question: NO, it has NEVER run well since i got the boat. i have only taken it out three times... First, as I detailed in my original post, when the overheat alarm sounded just a minute on the water... Second, taken to the water again only to hear the alarm again, except this time we left the boat on the trailer with the motor in the water, and didn't run it for that long... Third, just the other day, after the water pump/impeller replacement, and the alarm did not sound; but the boat sounded and ran but did not go beyond like 10mph.

...

as for this speed limiting issue, i'm trying my hardest to read thru this Clymer outboard manual and find what is causing the problem. the only thing i've been able to find so far is this mysterious "S.L.O.W. mode" which sounds like it might be the case, but who knows...

...

this really sucks because i'm 27 years old and i've wanted a boat my entire life--i've never had one, i was finally able to afford a used boat and my family was happy i got one (i was thrilled), and now all this mess....

BigTexNick, I asked my mechanic about that today and he said he doubts that's the problem...I'll try to talk to him again tomorrow, but I will be busy, so it may have to be Saturday...

I'm sorry, but it sounds like you were sold an engine with a known problem.