Power Loss 97 Merc Force

[msurma]

What are some possible causes for power loss when going over 3800 RPMs with a 1997 120hp Merc Force engine. (The boat is an 18ft Caravell Mid Console)<br /><br />All engine power seems fine until around 3800 RPMs, then it seems to suck in air and looses power-- I must then reduce speed and not go over 3800 RPMs or the same thing happens again. Any suggestions? Thanks.<br /><br />Mike

 

[JB]

Re: Power Loss 97 Merc Force

Howdy, msurma. We sure are getting a lot of power-loss-at-w.o.t. problems lately. The most likely causes are related to fuel delivery: hoses, pumps, squeeze-ball pumps. Less likely but still possible are ignition timing and strength problems. Your description sounds like a fuel delivery problem . . .and it's repeatability sounds like the squeeze-ball pump anti-siphon feature that is mentioned elsewhere on the board. Check out the other topics related to power loss. You will find a lot of good advice there that needn't be repeated.<br /><br />Good Luck.<br />JB

 

[msurma]

Re: Power Loss 97 Merc Force

Thanks for the info J.B. <br /><br />We checked pumps, hoses, squeeze-ball and all are in great shape. I should have mentioned that the engine doesn't actually loose power, but just starts sucking in air-- the boat seems to be angled in the air too much-- (porposing?) It may be a problem with planning or engine trim, but I can't seem to adjust the trim to get the boat to plane out. Could improper load distribution cause the porposing and cause the engine to suck in air at a certain RPM? We are new to boating and can't seem to figure this one out. Thanks for any and all help.

 

[JB]

Re: Power Loss 97 Merc Force

Hmmmm. Now it sounds like your engine is running out of torque without making it onto plane. Weight distribution could contribute to this, but it seems unlikely that it would be the only cause. Planing a boat is a bit like taking off with an airplane...it takes a lot more power to get it up than it does to keep it there. With that 120 your Caravelle should jump right up.<br /><br />Check your prop. There are two numbers stamped into the forward end of the hub. The second number is the prop pitch. With your Caravelle it should probably be 17 or 19. If it is higher, say 21, try borrowing a 17 from a prop shop and try that.<br /><br />Check your motor height. The anti-cavitation plate (the horizontal plate above the prop)should be even with the bottom of the boat and parallel with it at zero trim.<br /><br />If both of those are okay, you may be actually losing power at wide open throttle. Check out the other topics on this board about power loss at w.o.t. There are plenty, and the advice is as good for your Force as for the engines mentioned. By the way, the squeeze-ball problem only occurs when the fuel flow exceeds a certain point. The only way I know of to troubleshoot it is try a new ball.<br /><br />Good luck and happy boating.<br />JB

 

[msurma]

Re: Power Loss 97 Merc Force

Thanks again J.B. for the good suggestions.<br /><br />We will check them out and see if we can get to the bottom of this problem.

 

[msurma]

Re: Power Loss 97 Merc Force

J.B.<br /><br />Just wanted to thank you for your advice. We switched props to a 19 pitch (from the 23 pitch prop that was on the boat when we bought it). Made all the difference in the world- She now runs great at w.o.t! Thanks again.

<br /><br />Mike

 

[rivernut]

Re: Power Loss 97 Merc Force 120 ELPT

Re: Power Loss 97 Merc Force 120 ELPT

My son has this motor on his 20' Proline. He can run for 4 hours before his reduces the power to 2500 RPM, then go for another 2 hours, then quits all together. After waiting 2 hours it will run at 2500 RPM for about 10 minutes then quit again. After talking with Merc mechanic, it sounds like the Stator. He asked me if it is a red or black Stator, it is red. Just waiting for the new stator to arrive and I will post the results. This is the second week end for this to occur with the exact same symptoms. After the first occurrence we removed the thermostat to see if the engine will run cooler. We are in Maine in 55 degree water and the water pump is new and pumping at the max. Prior to the first power loss the boat went 25 hours total run time in same or similar waters. I too am looking for feed back.