Mercruiser 470 wont rev past 4200 rpm HELP

[Technorunner]

Re: Mercruiser 470 wont rev past 4200 rpm HELP

Im just speculating here.
But if the exhaust flaps tend to stuck MAYBE the higher resistance in exhaust flow would get it to hesitate. when the engine slowly revs up the pressure from exhaust flow get it to fully open. (IF you still have them ) otherwise the throttle linkage sounds like probable thing to check up on. ?Just looking at the throttle flap while someone put it at WOT to see that you really getting WOT. And the last thing would be (if there are any) if a vaccum hose have been missed or beeing full of oil or beeing soft so the vaccum pulls it together.
As always i hope you understand my english even if its far from perfect. Hope you get it fixed soon
//Andreas

 

[scv76]

Re: Mercruiser 470 wont rev past 4200 rpm HELP

just out of curiosity what size prop are you running? i run 14.25 21p and at 4300 im running like 44 to 46 depending on trim settings

Exactly!!
This is why I posted as above in post #17....If you are only getting 30 mph at 4200 rpms; well, that's just not right for an 18' deep V.
If you think it's a linkage problem, get a friend to go with you to steer the boat and shift into forward. Disconnect the linkage where it goes into the carb. and operate the carbs throttle plate by hand. You must have a fancy timing light, my old school light is a light only and I have to connect a tach/dwell meter to check rpms.

 

[Trunks]

Re: Mercruiser 470 wont rev past 4200 rpm HELP

yep check throttle linkages already and its all good... had that test done today of a matter of fact............ and i do not have exhaust flappers..... well i didnt before and i just installed them ... made no difference

 

[DACEAC]

Re: Mercruiser 470 wont rev past 4200 rpm HELP

I hear ya on the buggin the heck out of ya trunks. Have you by any chance tried advancing the timing 2 degrees? We did that with a 260 mercruiser we had in a 24 foot sea ray and made a world of difference in how it ran in the upper rpms

 

[Trunks]

Re: Mercruiser 470 wont rev past 4200 rpm HELP

yeah ... timing is right where it should be ...

 

[Wadewell]

Did you ever figure it out? Having about same issue. Runs great till about 3/4 throttle then I get nothing after but a boggy sound and about 4000 RPM at WOT My motor is a complete rebuild one with all new flamethrower coil rebuilt carburetor electronic ignition eccentric Cetra and now I can only get 25 mph out of my boat and no top and power I’ve tried many faxes anybody have any suggestions

 

[GA_Boater]

Did you ever figure it out? Having about same issue. Runs great till about 3/4 throttle then I get nothing after but a boggy sound and about 4000 RPM at WOT My motor is a complete rebuild one with all new flamethrower coil rebuilt carburetor electronic ignition eccentric Cetra and now I can only get 25 mph out of my boat and no top and power I’ve tried many faxes anybody have any suggestions

Please start a new thread. Trunks left 7 years ago, he won't answer.

Closed.