Throttle/shift cables? Something else?

[tipitina]

Twin 250efi mercs with no hole shot. Should fly off on hole shot but just gets to about 2000 rpms and sits. Pull back and slowly increase rpms and she runs fine with good wot at around 5800. Mechanic spent two hours lubing and working linkage and said replacing the cables would help even more. He is legit guy and I trust him but before I spend time and money replacing cables I want to make sure it isn't some kind if other weird problem.

Motors are 1996 offshore series

 

[CharlieB]

Re: Throttle/shift cables? Something else?

The likelyhood of all cables at once is slim to none.

Whats common to BOTH motors, fuel tank, filters, hoses, battery and cables?

Start cleaning battery cables, EFI's are sensitive to voltage and poor cable connections have caused many complaints.

Fuel hoses, fitting, filters, can reduce fuel flow and cause reduced power, maximum fuel flow is required for acceleration, more than even WOT running. Most likely will turn out to be reduced fuel flow somewhere between the tank and motors.

 

[tipitina]

Re: Throttle/shift cables? Something else?

Thanks for the advice! Batteries and fuel hoses are each independent of each other as well. Batteries are brand new and seem to hold and provide solid voltage. The boat had sat for quite sometime and when first getting it going again the throttles were very hard and stick feeling. Running it has seemed to loosen them up and make it better, but the fuel hoses theory makes good sense as well. Is there a way to check/clean them? I did check the fuel filters, both the transom mounted and the engine mounted and no major debris but they are all cleaned up. Motors are turn key and start right up, idle fine, and seem to run great. It does just seem you have to slowly accelerate to build speed as opposed to the hammer down that I am used to in other boats. Sorry for the long post.

 

[CharlieB]

Re: Throttle/shift cables? Something else?

Disconnect the fuel hose immediately after the primary fuel pump, crank the motor and see if you get a nice fat pulsed fuel flow on each engine. Aged hoses can deteriorate and reduce flow. It's one thing that you can rule out.

How old is the fuel? Aged fuel will reduce power.

The answer has to bee common to BOTH motors, cables ain't it even tho they may be stiff and in need of replacement, they will not limit pwer on acceleration, that is either a reduction in fuel flow or ignition timing, and I can't see BOTH motors having the same ignition problem at the same time. That leaves fuel, and there again it must be aging, of the fuel itself, or the hoses or a common fitting. Do both draw off the same fuel tank, maybe from the same pick-up fitting?

 

[tipitina]

Re: Throttle/shift cables? Something else?

They both draw off same tank but each have independent lines. I'll drain what fuel is left as I can't speak to the age of it. Or would toppIng off with fresh fuel suffice? I estimate there is around 30 gallons in a 150 gallon tank.

Thanks again for your help.

 

[CharlieB]

Re: Throttle/shift cables? Something else?

Sour fuel will accelerate aging of fresh fuel.

You might try using a 5 gal aux tank, rig fuel hoses from each motor to the tank, run it a couple of minutes to use the old fuel in the lines and the motor, then accelerate to see if the fresh fuel makes the difference.

Fuel hose and primer bulbs deteriorate and should be replaced whenever they start feeling 'stiff' or show signs of weather-checking or cracking.