Motors won’t go over 3,000 rom

DarrenC

Member
Jul 10, 2018
161
Boat Info
2001 Sea Ray Sedan Bridge 400
Engines
Mercruiser horizons 350
I have a 2001 sea Ray Sundancer 310. The motors won’t go over 3000 RPMs. We thought we had a low fuel pressure problem but after checking with MerCruiser the fuel pressure they said should be at 30 psi which it is. We replaced the fuel pump Fuel cooler fuel regulator and still nothing. Today I had another mechanic put a diagnostic computer on it and it read nothing wrong however the timing was off on both motors one was overcompensating. Timing was reset to where it should have been at factory marks on Motor. Before doing this I was getting 4200 rpm’s out of starboard motor and only 3000 on port motor after adjusting timing I’m only getting 3000 RPMs on both motors at sea trial. Can anyone anyone suggest anything? We are at a standstill and I don’t know Which way to go. Thank you in advance
 
I have a 2001 sea Ray Sundancer 310. The motors won’t go over 3000 RPMs. We thought we had a low fuel pressure problem but after checking with MerCruiser the fuel pressure they said should be at 30 psi which it is. We replaced the fuel pump Fuel cooler fuel regulator and still nothing. Today I had another mechanic put a diagnostic computer on it and it read nothing wrong however the timing was off on both motors one was overcompensating. Timing was reset to where it should have been at factory marks on Motor. Before doing this I was getting 4200 rpm’s out of starboard motor and only 3000 on port motor after adjusting timing I’m only getting 3000 RPMs on both motors at sea trial. Can anyone anyone suggest anything? We are at a standstill and I don’t know Which way to go. Thank you in advance
 
Motors are mercruiser 5.7 horizons serial #OL 670529 OL 671965
 
when both engines are behaving badly at the same time one of the first things I start to suspect are the props, especially on a 'new to you' boat where you don't know the history of the boat....

might want to insure the props are the wright size and pitch for that drive train....Sea Ray can tell you what props should be installed if you don't have the owner's manual....

cliff
 
Lots of similar issues around here lately, lots of them have reported major improvement or total repair by just doing tuneup. When’s the last time you did plugs/wires?
 
How is your bottom for growth? Props? We had that issue when our bottom paint reached the end of its life. Growth on the hull we couldn't see... engines just couldn't combat it. Haul out, clean, paint. All good.
 
I looked at previous repair records and in 2016 it was recommended that the props be resurfaced to get full rpms out of motors. I think that is where I will start. Thank you I appreciate it.
 
How is your bottom for growth? Props? We had that issue when our bottom paint reached the end of its life. Growth on the hull we couldn't see... engines just couldn't combat it. Haul out, clean, paint. All good.
Bottom was soda blasted and painted on 5/18/18 but hasn’t been used so maybe some growth. I’ve noticed A lot of orange growth on everything here in and Bedford Massachusetts home of moby Dick this year.
 
Bottom was soda blasted and painted on 5/18/18 but hasn’t been used so maybe some growth. I’ve noticed A lot of orange growth on everything here in and Bedford Massachusetts home of moby Dick this year.
New Bedford
 
Lots of similar issues around here lately, lots of them have reported major improvement or total repair by just doing tuneup. When’s the last time you did plugs/wires?
Plugs done 2 weeks ago.. don’t know when wires were changed they look fairly new
 
How old is the gas? It could be knocking and the knock sensors are kicking in to retard the timing, this will also limit your RPM's to around 3,000. If the timing was adjusted to give it more advance this could have made the knocking worse.
 
How old is the gas? It could be knocking and the knock sensors are kicking in to retard the timing, this will also limit your RPM's to around 3,000. If the timing was adjusted to give it more advance this could have made the knocking worse.
Timing was adjusted to factory setting. Starboard motor was over compensating.
 
Darren, look for my response in the other thread you posted on this topic. I ask some questions you need to answer for yourself before you do anything to the props.

There was a thread on here a couple of weeks ago from a guy having a similar issue. He stated had a mechanic look at the motor and he tried all kinds of things to correct the issue but nothing worked. It was then suggested he get a certified Mercruiser Tech to look at it....he did and the Tech solved the problem in 20 minutes. Most Mercruiser guys know Mercruisers....that's what they are trained for. Might be time to get the expert to the boat and let them have a shot.

FWIW surfacing a prop (whatever that means) isn't going to really do anything. You need to find a prop shop with something like PropScan which is a computer program the will fully measure all the blades and match them for the optimum performance. I've had it done on 16" props and 24" 4-blades. When done right the difference is amazing but, for the props to work right everything else must be right.

Good Luck with everything.
 
Fuel injector dirty or clogged, I have a 2005 8.1 496 where merc painted the inside cool fuel pump and paint chipped off and got stuck in the injectors. I had the same thing would not pass 3000n rpm.
 
Does your boat have Smartcraft, I recently bought my 2003 240SD and while test driving it would run for a little bit then it would feel like it was bogging down and only run at about 2500 RPM no matter what we did. We took it back and the dealer checked everything and said it had went into Guardian Mode. I don't know a lot about boats but he said that when it is having a major malfunction the smart craft will try to protect the engines by restricting RPM and gas flow. After checking all the codes they found out that the oil pressure sensor was bad, they replaced it and the boat seams to run fine now. Now I will tell you that the dealer could have fed me a line of bull and I would never know. I know how to drive a boat not work on them.
 
Darren,

I dropped out responding because the story keeps changing.

-First, it was a fuel pressure problem in another thread that made little sense. Your fuel injected engine can't run on 20 psi which you indicated it did in the other thread.

-Second, you have a technician hook up a scanner and he sees no problem with either engine except for timing. He adjusts the timing and now both engines won't go above 3000 rpms. That would suggest that if he set the timing for the port motor to match the starboard (opposite of what he did)...both would be running at 4200 rpm. What is the process your technician used to set the timing and what did he set it to?

CSR is a great forum to help solve problems but credibility is important.
 
Bottom was soda blasted and painted on 5/18/18 but hasn’t been used so maybe some growth. I’ve noticed A lot of orange growth on everything here in and Bedford Massachusetts home of moby Dick this year.

This is a long time for a boat to sit in salt water in New Bedford and not be run. I suggest hiring a local diver to clean the running gear and props. I'll bet your problem will resolve itself then.
 
This is a long time for a boat to sit in salt water in New Bedford and not be run. I suggest hiring a local diver to clean the running gear and props. I'll bet your problem will resolve itself then.
Diver went down today bottom and props were clean scraped off anything he saw. Props being pulled tomorrow to check size and recondition. We think wrong props are on it.
 
We test drove it today same thing.. gas could be stale so I put additive in and filled tanks with fresh gas
 

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