I cant get more than 2400 rpm's

[spinakersheet]

I have a 1986 volvo-penta aq125. I don't know if its an a or b.<br /><br />I have a rebuilt carb, new plugs, points, rotor condenser, coil. All the compression is 165-170.<br /><br />It runs great up to 2400 rpms under load with one person in it, and it just wont go any faster. I am probably doing 10-12 mph tops.<br /><br />In neutral not underload It goes to 5000 rpms easy.<br /><br />I took the engine cover off while I was accelarating and the throttle is going all the way down.<br /><br />The prop looks like its stock. I don't think I could be loosing over 2000 rpms because the pitch is a 19 vs. 17. If thats the case.

 

[sony2001]

Re: I cant get more than 2400 rpm's

Fuel pump?

 

[Gene70]

Re: I cant get more than 2400 rpm's

Let's start with first things first. Your prop is wrong. 15x17 is the highest pitch you should use. You might even have to go lower. On your fuel one of the most overlooked problems is the fuel vent and check valve. It might seem odd but check your fuel vent this way. Put your lips around the vent outlet and blow through the vent. Remove the gas fill plug. You may hear the fuel bubbling. Next get to your fuel tank at the fuel line fitting going to the tank. If the fitting is aluminum remove it. There is a check valve there. Remove fitting and throw it away. Get a 1/4" pipe thread to 3/8" barb fitting. Install new clamp. Check both these valves and replace them and you should be fixed. Your engine is just starving for gas. This is a lot cheaper than a new fuel pump and I believe this is your problem.

 

[snapperbait]

Re: I cant get more than 2400 rpm's

Gene 70: BAD IDEA on throwing away the check valve. It's there for a reason. It prevents the engine from siphoning fuel while its not running.A.K.A FIRE HAZZARD!!! Always replace it with the same type...It's U.S.C.G. Regulation..

 

[spinakersheet]

Re: I cant get more than 2400 rpm's

Thanx. I will check the flow of the fuel pump today. <br />Is it possible that you could lose 2000 rpms with an oversized prop?<br /><br />Do I have to put a vovo-penta fuel pump in? <br /><br />Would it be better to put an electric fuel pump in?<br /><br />My rebuilt carb has about 5 hours on it. I just recleaned it and when I put back on I lost that hesitation from forward idle to acceleration. Do you think its the throttle cable or I need a new fuel filter?

 

[hdlowrydr85]

Re: I cant get more than 2400 rpm's

I ran into this problem on an '85 omc out drive, the exhaust flapper was stuck closed. With the cover off the engine and remove the air cleaner when running under load, do you see gas or even exhust coming back up and out of the carb? The engine will sound like it is under a very heavy load snd working very hard.

 

[hdlowrydr85]

Re: I cant get more than 2400 rpm's

one more thing, check the choke adjustment when running under load, if it is not all the way open you will be able to get going. If you are starving the engine for fuel, it should be backfiring through the carb. I don't think you are starving but possible flooding or the engine is not breathing correctly.

 

[spinakersheet]

Re: I cant get more than 2400 rpm's

my timing chain was off by two teeth therefore my timing was off. It has since been corrected and I got over 4000 rpm. Now<br /><br />But, I would get backfire going from forward idle to excelleration. And under heavy load 7 people in an 18 foot boat At high rpms I Lost power and had grey smoke I lowered the rpms it ran fine and ran it for about another hour at forward idle then after a total of 3 1/2 hours it just died. no sputtering just stopped. It has plenty of gas and gas is getting into the carb. it looks like there is spark. <br /><br />I cant get it started. any suggestions?

 

[Bob_VT]

Re: I cant get more than 2400 rpm's

Timing would be a starting point. Get the timing and the chain right. Once those are corrected then move onto the fuel system. On your fuel pump there should be s plastic vent line. Is there any fuel present in it? On a marine fule pump the plastic line vents to the crankcase. This is the marine substitute for a weep hole that is found on an automotive fuel pump.<br /><br />I just this morning replaced my fuel pump due to it dropping dead on the lake yesterday. I was unable to get more than 2000 rpms but that was sufficient to get me to shore. New pump, problem fixed.<br /><br />Bob

 

[spinakersheet]

Re: I cant get more than 2400 rpm's

Possibly the fuel pump if there is gas in the fuel filter and gas coming out of the jets does that mean the fuel filter is working?

 

[Bob_VT]

Re: I cant get more than 2400 rpm's

Yes, but marine fuel pumps have double diaphrams and you may not be getting full capacity. <br /><br />Bob

 

[spinakersheet]

Re: I cant get more than 2400 rpm's

I am replacing the fuel pump today. <br /><br />It still seems like I am getting a weak spark.<br />It is a new coil, points, rotor and condenser. <br />Also new plugs. They are dry. The stem of my coil is thicker than the rubber cap that is supposed to go over it. <br /><br />The spark is white not blue. The resistor wire is working. It is 10.5 on + side and not even 1 volt on the - side.

 

[spinakersheet]

Re: I cant get more than 2400 rpm's

It was the coil. Even though it was only 3 weeks old it was those same mechanics who burned out my points, broke my rotor, had my timing at 30 when it was supposed to be at 10. Also, put in the wronge coil. I need one with an internal resistor since it didn't have one. It burned it out. I put in a new coil and it fired right up. No flat spots at all.<br /><br />Thanks for everyones help.