mariner 150 won't rev

[SCOTT671]

can any one give me some advice just rebuilt my powerhead runs fine but won't rev over 5500 rpm
before i rebuilt it
it would rev to 6200
any thoughts or advice

thanks

[Techteam]

Sure it's on six ?

Check the basics from the beginning. Butterflys timing and sync. Try not to be too hard on it until you find out whats wrong. If you dont find anything obvious post again and we can dig a little deeper. To be honest a post like this is kind of difficult to advise on without a lot more information.

[SCOTT671]

yep defiantly firing on all 6
carbs all balanced all opening fully
i am running the same prop and same transom height
less weight in the boat

[Matt]

Assuming it's an older carb or efi with stator, trigger & switchboxes - Did you replace the switchboxes, and are they OEM?

[SCOTT671]

Originally Posted by Matt

Assuming it's an older carb or efi with stator, trigger & switchboxes - Did you replace the switchboxes, and are they OEM?

yep its old v6 carb oem equipment ie electrics and vertical reeds

[Matt]

Oh, OK. FYI, Sierra switchboxes have 5500 rpm rev limiters in.

[SCOTT671]

could the motor still be a bit tight after rebuild only done about 2 hours on the water

[Cookee]

Originally Posted by SCOTT671

could the motor still be a bit tight after rebuild only done about 2 hours on the water

No! That's would be tighter than ..................... well very tight!

[Techteam]

Timing is set to ?

[SCOTT671]

Originally Posted by Techteam

Timing is set to ?

i think the timing set exactly the same as when i took it apart marked it all up as the last one of these i rebuilt was about 20 years agowhen i had more hair and youth on my side

[Techteam]

I'd check the timing anyway, I know you say its on all 6 but are you sure? or does it just sound like it's not missing. If you have another set of plugs I'd swap them out just to check. I've had a bad plug before which strangely didn't produce a misfire but wasn't firing strongly enough at full throttle to give a good burn.

[SCOTT671]

Originally Posted by Techteam

I'd check the timing anyway, I know you say its on all 6 but are you sure? or does it just sound like it's not missing. If you have another set of plugs I'd swap them out just to check. I've had a bad plug before which strangely didn't produce a misfire but wasn't firing strongly enough at full throttle to give a good burn.

is there any chance you would have or know the timing settings for my motor as i only had th toque settings
this would be a great help
many thanks
scott

[Burty]

25 degrees i guess

[Brookp01]

Originally Posted by Techteam

I'd check the timing anyway, I know you say its on all 6 but are you sure? or does it just sound like it's not missing. If you have another set of plugs I'd swap them out just to check. I've had a bad plug before which strangely didn't produce a misfire but wasn't firing strongly enough at full throttle to give a good burn.

Does sound like it's running on 5 cylinders. The 500 to 700 rpm drop off has happened to me twice, both times was a coil. They crack easily and despite advice to the contrary cracks in them do cause failure at full throttle.

[SCOTT671]

coil breaking down i noticed a blue light inside the installation on the positive to the coil so as the motor was getting warm the wire was parting and breaking down but it was OK when cold hence why i said it was firing on all 6

thanks again

Scott