why I cant get to top speed

hourmouzis

I own a 2007 Rinker EC330 I purchased new in 2010: has 350 MPI sea-core engines DTS controls with Bravo 3 drives
Top speed was about 42 MPH,
Beginning of last season first time out would not get above 30 MPG for about 30 minutes, then engines RPMs went to normal and boat ran good all year. This year wont go over 35 MPH, very hard to get up on plane: I Replaced fuel filters, added fresh gas and fuel additive, cleaned fuel arrestors ,
engines have 168 hours on them. I was told to replace cap/rotor and plugs, but to me it feels like not enough fuel/air, any ideas??

aero3113

Welcome to the forum! You can also check the bottom of your hull and props for growth and make sure your trim tabs are working. 

randy56

If you are up to RPM's it's probably dirty bottom, algae, slime, will slow you down. 

Wildboating

I agree with Randy,  we need to understand your Rpms at these speeds to offer any assistance or advice. 

hourmouzis

Thank you for your input,
My bottom is painted and i am in fresh water on the Delaware river
I am also a diver so I can go under and check it, will advise

bry1429

I keep my boat in very clear water. I am surprised at how much growth can grow on the bottom in a matter of a few days in a clean water environment. the clearer the water is the more Sun gets through and helps the growth.   I go to the beach every few weeks with a scrub brush and scrub the bottom and the lower units, it's surprising how much more speed/get up-n-go you get after a good cleaning. 

hourmouzis

So this weekend, checked computer, no codes, Fuel pressure is fine, no growth under boat, I am having new plugs, cap and rotor installed, will see what happens after that. Thanks

JPCRUZE

Check your props, similar problem happened to me. I pulled the boat and the props were chewed up and needed to be welded and returned and now everything is back to normal

hourmouzis

I Checked props when I checked the bottom of the boat, all good.

hourmouzis

I checked fuel pressure on the manifold, manual says it should be 43 PSI, I have 60 PSI, is that OK?
If not how to I correct?

Wildboating

I do not have your serial number or specs, but if you are certain that you are supposed to be at 43 psi (sounds correct) then your fuel pressure regulator has failed.   It is supposed to relieve the fuel pressure and return the excess psi to the fuel water separator.  If this is not happening you are getting way to much fuel in your cylinders and you are running rich.  This would definitely cause a loss of power and poor performance.   Pull the regulator, there is a screen that is likely plugged on the bottom, otherwise replace regulator.

Michael T

@hourmouzis .....also pull a spark plug if  your engine is running that rich the spark plugs should be black and even have unburnt fuel smell and residue.

Wildboating

@hourmouzis

I will elaborate a bit more.  The fuel pressure regulator is located in the cool fuel module on the lower port side of the engine in a black box.  Basically underneath the engine.   The engines ecm operate'a the injectors via a pulse width telling them to open for a certain amount of time.   Your fuel psi is supposed to be 43, the amount of fuel you will receive at 43 psi for say 5 milliseconds is less than what you would receive at 60psi for 5 milliseconds.    Furthermore, our high pressure pump actually creates about 100psi of pressure, the fuel pressure regulator is bleeding the excess off back to the water fuel separator via the return line.  If your pressure is too high this is a easy issue to identify.   I'm going to say regulator is fine because you are bleeding some pressure off but most likely your return screen is clogged.  This could be part of a bigger issue known with cool fuel 3 modules and ethanol eating the paint coating off and clogging regulators, injectors and so on.  Get the module off and inspect. 

Michael T

Also remember the cool fuel module has TWO filters a pre and post.

hourmouzis

Thank you for your input, makes sense, where is this screen located that you assume is clogged?
I have replaced both filters in the cool fuel module, I just replaced all the plugs, cap and rotor this week, but have not taken her out yet. Fresh fuel (filled) and additive

The plugs were black, and the cap and rotor where pitted
Yes the exhaust smells rich and has for a while.
I have all the manuals for the engines and have the parts manual for the fuel supply module but do not see any screens
To replace the regulators are about $125 each cost, If I have to do that Im ok with that

Ill take the lines apart and see if I can find the screen, bottom line is I assume if the manual says 43 PSI, it should be 43 PSI, and not 60, is that correct?
Engine Serial # 1A030234 and 233

Thanks again

Wildboating

Just remove the regulator, on the bottom of it is a screen that allows the fuel to pass back to the water fuel seperator.   Fuel enters one side, vaccum the other and relief pressure out via the bottom through screen back to water fuel seperator.   I hate to say im 100% on this, but all the data you have provided says you will find your problem there.

Wildboating

This is the cool fuel pressure regulator, not the one on the fuel rail.

Wildboating

Another quick test if you would like.   Put your fuel pressue gauge back on, then watch the fuel pressure at idle.   Remove the vacumm to your cool fuel regulator and fuel pressure should rise.  I bet it won't, because it is up already as you are not able to bleed of the excess pressure like you should be.

hourmouzis

Update
After replacing the plugs cap and rotor, boat runs like new.
The fuel pressure was at abut 50 psi at idle.
Thank you all for your help but it seems that it was just needing a tune up.
Funny thing I tried to higher the local mechanics who didn't get back to me in three weeks so I did it myself and saved a few bucks....

Wildboating

So your fuel pressure is not 60PSI?  Even 50 psi is high at idle.  You should be around 38.