Mercury 150 hp 1500 series engine trouble..

[curtis63]

I just bought a boat and LOVE IT, unfortunately, it has a bit of a problem. Most of the time when I try to go, the engine sputters and dies when I try to run it faster than 1400 rpms. It's like it's choking and can't go any faster without dying.

However, some of the time, I'll start accellerating, and the engine will run PERFECTLY !! I'll be buzzing along at about 35mph across the lake with no problems, no sputters, no hesitation. It just works great.

Then, when I turn off the engine to do some fishing, or trolling with my trolling motor, and start it up again and try to go, I get into the same problem where it won't go over 1400 rpms without just dying. I can have it steady around 1000-1300 rpms and it will run a bit rough, but it will die when I try to accellerate past 1400 rpm.

Then again, when I turn it off for a while, and restart it, it will sometimes work fine and dandy without any sign of problems.

I just can't figure it out. As long as it's not in gear, I can rev the engine and it wont ever sputter, but when it is in gear, I have about a 20 chance of it actually letting me run it over 1400 rpms.

Again, once it gets going, there is no problem at all, it seams like something must not be engaging correctly when I put it into gear most of the time and it just can't handle going over 1400rpm, but it's just unpredictable when it's going to work great, and when its going to choke at 1400 rpm...

As a side note, the hydrolics has a leak somewhere in the system so when it runs low, I cannot lift or lower the engine. Not sure how hard that is to repair. Could the hydrolics problem be related to the engine trouble ??

Any help anybody could give me with this problem would be GREATLY appreciated.

Thanks a bunch,
Curtis

 

[Chris1956]

Re: Mercury 150 hp 1500 series engine trouble..

Curtis, The PTT leak has no effect on the acceleration issue.

Is that motor an inline six? If so, it is from 1977 or older, BTW. The following has mostly to do with the inline six model.

Likely the issue is water intrusion, carbs or fuel pump. Check the plugs. If any of them look brand new, in comparison to the others, it may be getting steam cleaned by water intrusion. If they are all black and oily, then water intrusion is not the issue. next check spark on all clyinders, to rule out bad spark plug wires. If all six fire consistantly at idle, they are likely fine.

Do you have any idea if the boat sat a while before you bought it? If so the carbs may be gummed up. If they are clean, the idle mixture may be off, or the fuel pump may be leaking. Remove the two pulse hoses on the fuel pump and see if fuel comes out of the pulse fittings, when you pump the primer bulb. If so, the feul pump diaghram has a leak and you need to rebuild the fuel pump. if all this stuff (Spark, no water intrusion, fuel pump) check out OK, the carbs are next.

You can try to richen the idle mixture 1/8 turn top carb first, mid carb next and bottom carb last. Try to accelerate in between each adjustment. when you get consistant acceleration with a reasonable idle, you are done.