Logo

Mercruiser 81S HO Loses Power at 2500 RPM

regal7

New member
I have a Regal 4160 with twin

I have a Regal 4160 with twin IO V Drive Merc 8.1S HO engines. One engine loses power between 2500 and 3000 RPM when it is underway seems to act like it is cutting out. If I rev the engine in neutral the engine can go to Max RPM. Any suggestions?
 
"Dirty fuel or filters?
Mpi e


"Dirty fuel or filters?
Mpi engines, right?
So which are they, IO or V drive?
You should not be revving to max rpm in neutral.

Rod"
 
"If I rev the engine in ne

"If I rev the engine in neutral the engine can go to Max RPM." Big NO NO; limit neutral to 1500 RPM. Start w/new fuel filters and a clean flame arrester.
 
"your a retard for reving the

"your a retard for reving the engine to MAX in neutral...check fuel filters,water seperator,plugs...carbs may need to be cleaned or rebuilt!!!!!!!"
 
"Your Momma,

I think you ne


"Your Momma,

I think you need yoh mamma with some good mouth soap!

Keep the snide remarks to yourself.

Who died and left you JUDGE!"
 
Sorry to confuse the group...

Sorry to confuse the group...

Inboard V Drive Merc 8.1S HO (MPI)
Not MAXing RPM...Gotcha.
Just not running poorly in Neutral only under a load and above 2500 RPM
 
"Could be bad plugs or wires.

"Could be bad plugs or wires.
Could be dirty injectors.
Try a can or two or auto injector cleaner in the gas, or alternatively SeaFoam works well I hear from others on this board.

How are your filters?


Rod"
 
"Kim, Do you hear a beep from

"Kim, Do you hear a beep from your alarm when you key on? You should be setting off the alarm with that neutral overspeed.Have that engine scanned for faults. sounds like you have issues that are setting off a guardian mode. Do you have any smartcraft guages? do they show a fault? this is a computer controled engine, you will have to talk to the computer to see whats going on. good luck"
 
I would pour a 1/2 can of Sea

I would pour a 1/2 can of Sea Foam or injector cleaner right into an emptied fuel/water separator filter to give the injectors a strong dose of cleaner.
 
Thanks for the tips. Your insi

Thanks for the tips. Your insight is very helpful.

New fuel/water separator filter installed last week no change in performance. Is there more than one? Will try Seafoam. Will replace the plugs. There is a beep when turning the key on. The fuel pump runs same as the other engine. This is a Smartcraft engine but do not have gauges. Will get this engine checked out by Mercruiser tech if the plugs and Seafoam do not fix.
 
If you were going into Gaurdia

If you were going into Gaurdian Mode you would have an alarm. So the most likely cause is fuel restriction. The next thing to do would be to get ahold of a fuel pressure gauge and check to see if the fuel pressure drops off when the problem occurs.
 
"If you have an inline filter,

"If you have an inline filter, it would be for a boost pump. I bet you have a bad boost pump. I saw a 502 do the same with thw bost pump unpluged.
Dave n is right . No alarm no Guardian mode"
 
Back
Top