150hp Mercury v6 early 80's. Idles fine but?

Question

But in open water it will not rev up only very little then it just holds there about 1500 rpm. I squeezed the bulb and no change. Any sugestions? I did clean the carbs.

Answer 1

Could be any of the above, but I had a Johnson 225 at one time, which suddenly refused to rev above about 2000 rpm.

It transpired that the little carb throttle linkage had vibrated loose, and hitting the end-stop too soon.

A five minute fiddle with re-adjusting it, and all was well !

Answer 2

do you mean it idles at 1500.  Thats not to bad.  If your saying it won't go higher when you apply the throttle.  the cable could be bad carbs bad ignition bad ect.

Answer 3

Did you check the throttle linkage for full travel along with ignition advance? How old is the fuel supply line. It could be falling apart inside. How about the fuel pump diaphragm, just a little pin hole is all it takes. Are you getting strong spark on all cylinders? Fuel filters? Does the primer bulb collapse?

Answer 4

try changing the fuel filter and the air filter

Answer 5

Sounds like your switch box. Just a hunch, but I think your on limp mode. Nice feature if it burns out on the water you still have low rpm side to get you home..........Not as simple as a sink and link, it would rev higher don't you think ?

Answer 6

Rebuild the carbs, new jets, springs spacers and gaskets.  

Check fuel lines for any possible leaks, could be sucking air, but more likely carbs.

Are you having the same problem when in neutral?  If so fuel flow is still likely, if not, you may have a lower unit issue.