Max RPM 4,000

[Bob L.]

I have a 2002 280 Sundancer. 498 Mercruiser Mag with Brovo III lower unit, single engine. Problem I can not get full RPM. Fire engine up, purr's like a kitten, no skip, no sputtering. Pull away from dock leaving marine low RPM, same purr, no skip, no sputter. Get out put throttle down goes up on plan, but can not get more then 4000 RPM. Same purrs, no skip, no sputter sounds great. Throttle handle pushed all the way down. Changed fuel filter did go to 4100 RPM, but that is it. Any ideas? Like to stay out of shop so I don't have to B.O.A.T. brake out another thousand. LOL

 

[JimG]

Do you trim up? That will give you more RPM/speed.

Your RPM at WOT should be 4800.

Welcome to your first post on CSR!

 

[Bob L.]

Yes, trims were up. Before I could reach up to 5300-5500 RPM Tops speed 45-46 MPH in flat water. 4100 RPM only getting 20-22 MPH

 

[aneely]

Is 5300 - 5500 within the engine specs? What is the size and pitch of your prop? Is it the same prop as when you were getting the higher speed?

 

[Do Over]

put plugs in it....496's are notorious for em

 

[Bob L.]

Yes, same prop did not change it. Specs recommend 3100-3200 RPM for best fuel economy.

 

[Lazy Daze]

Yes, trims were up. Before I could reach up to 5300-5500 RPM Tops speed 45-46 MPH in flat water. 4100 RPM only getting 20-22 MPH

Something is not right with that. If I remember correctly, the rev limiter kicks in at 5,000RPM. It could be a poor reading tach, could be not remembering it correctly?

As far as what caused your lower RPM, there are probably hundreds of threads about this and you can search for more info on this. But, basically...

Assuming there's no "user error"...

-- First eliminate dirty bottoms, damaged props, stuff wrapped around the props, etc.
-- When you replaced the fuel filter, what was the condition of the fuel inside?
-- Then move on to, as mentioned above, a tune-up

Most times, one of the above fixes it.

 

[dwna1a]

How old is the fuel? When was the last tuneup? When was the breather cleaned last?

 

[Do Over]

just a follow up to my suggestion of plugs......when I bought my 340 it would only rpm to 3200 (twin 496's)......put plugs and fuel filters in it ......4600....you've done the filters....now your gonna get as many suggestions as there are members here.....put plugs in it.

OR let's start with...."when was the last time you put plugs in it"?

 

[FootballFan]

Agreed on the plugs. Had the same issue on my 340, initially blamed it on old gas - new plugs - problem fixed.