Could auto pilot be stopping my boat from good by past 3,000 rpm?

DarrenC

DarrenC

Member
Jul 10, 2018
164
Boat Info
2001 Sea Ray Sedan Bridge 400
Engines
Mercruiser horizons 350
I’ve posted a few posts over the Last week trying to figure out exactly what is wrong with my 2000 and1 C Ray Sundancer 310. Boat will only go 3000 RPMs at half throttle not allowing it to go up on plane and nothing from half throttle till full. So far I’ve changed Fuel pump fuel cooler fuel regulator new plugs new water separator filter had bottom them inspected for Barnacles removed props confirmed correct size had them reconditioned had a computer diagnostic hooked up to Motors, And still nothing still will not go over 3000 RPMs not allowing it to get on plane. Does anyone know anything about auto pilot? What auto pilot stop my Motors from going over 3000 RPMs? As you can see I’m reaching for any answers. Thank you in advance to anyone who can help I sincerely appreciate it.
 
Darren,

Starting multiple threads on the same problem doesn't allow the viewers to see the history of what you have tried and not tried. It also covers up where responses don't make sense.

So to answer this question......it is unlikely that the autopilot has anything to do with this since it can be switched off.

In your first thread on this subject, you stated that one engine ran up to 4,200 rpm with no problem. Now it appears both won't go over 3000. Which is it?

You also indicated that you had a mechanic with diagnostic equipment hook up to the engines and he could find nothing wrong other than the timing on the "good" engine being set wrong. When he set it "correctly" the good engine refused to go over 3000 rpm. Is this true?

You say you have checked the props and the bottom is clean which brings you right back to the engines.

It's just my opinion.....but you really need to take the suggestion given to you in the first thread which was to get a Mercruiser mechanic to spend an hour to find out what is going on with your boat.
 
No

Autopilots are not interfaced with the engine controls other than at the hydraulic ram and that is only at the hydraulic lines leading to the 2 ends of the ram.
 
Long shot here but it did happen to me on my 270DA single 454. There was a fuel shut valve, somewhat like an ice maker valve on my boat that had started to vibrate closed. Boat was running fine. Shut it down for some reason. stated back up, ran fine until about 3000 rpms. Took my about 15 min. looking for it bobbing up and down.
 
PlayDate said:
Darren,

Starting multiple threads on the same problem doesn't allow the viewers to see the history of what you have tried and not tried. It also covers up where responses don't make sense.

So to answer this question......it is unlikely that the autopilot has anything to do with this since it can be switched off.

In your first thread on this subject, you stated that one engine ran up to 4,200 rpm with no problem. Now it appears both won't go over 3000. Which is it?

You also indicated that you had a mechanic with diagnostic equipment hook up to the engines and he could find nothing wrong other than the timing on the "good" engine being set wrong. When he set it "correctly" the good engine refused to go over 3000 rpm. Is this true?

You say you have checked the props and the bottom is clean which brings you right back to the engines.

It's just my opinion.....but you really need to take the suggestion given to you in the first thread which was to get a Mercruiser mechanic to spend an hour to find out what is going on with your boat.
Click to expand...
 
I feel like the question "did it ever run right" has come up in all of these threads but hasn't yet been answered? Maybe I missed it.

I'd never do this myself but can you get the engines above 3k in neutral? Might be telling.
 
Starboard motor would go to 4,200 rpm a mercruiser mechanic hooked up a computer t motors he found that starboard motor timing was advanced causing motor to over perform that is why after he adjusted timing to factory spec it only does 3,200 rpm now. Port side timing also was adjusted this is motor I had problem with from start still only does 3,000 rpm. Sorry for the confusion and thanks for your help.
 
Stee6043 said:
I feel like the question "did it ever run right" has come up in all of these threads but hasn't yet been answered? Maybe I missed it.

I'd never do this myself but can you get the engines above 3k in neutral? Might be telling.
Click to expand...
Engines do not go over 3,000 since I bought it 3 weeks ago. Previous owners were very older in age and never opened boat up. I have reports stating boat ran over 4,000 rpms and a friend tested this boat out before winter and went on plane no problem so answer is yes it has gone over 3,000 rpms
 
Stee6043 said:
I feel like the question "did it ever run right" has come up in all of these threads but hasn't yet been answered? Maybe I missed it.

I'd never do this myself but can you get the engines above 3k in neutral? Might be telling.
Click to expand...
Motors rev way over 3,000 in neutral no problem
 
Stee6043 said:
I feel like the question "did it ever run right" has come up in all of these threads but hasn't yet been answered? Maybe I missed it.

I'd never do this myself but can you get the engines above 3k in neutral? Might be telling.
Click to expand...
Engines rev way over 3,000 in neutral
 
Stee6043 said:
I feel like the question "did it ever run right" has come up in all of these threads but hasn't yet been answered? Maybe I missed it.

I'd never do this myself but can you get the engines above 3k in neutral? Might be telling.
Click to expand...
Engines rev to 6,000 no problem in neutral. It ran ok last season has not this season.
 
Isn't boat ownership great!!!

Silly question but do your trim tabs work? Can you plane with the tabs full-in at 3k?

I don't know if this was previously covered but I owned a 340 that didn't love to run full RPM/plane each spring when I was working the stabil through the fuel system. It was both engines. Both engines behaved exactly the same until I got some of the old gas out, new gas in and put some hours on at sub-optimal RPMs. This was a spring reality for me. Maybe I was using too much stabill.....:)
 
Stee6043 said:
Isn't boat ownership great!!!

Silly question but do your trim tabs work? Can you plane with the tabs full-in at 3k?

I don't know if this was previously covered but I owned a 340 that didn't love to run full RPM/plane each spring when I was working the stabil through the fuel system. It was both engines. Both engines behaved exactly the same until I got some of the old gas out, new gas in and put some hours on at sub-optimal RPMs. This was a spring reality for me. Maybe I was using too much stabill.....:)
Click to expand...
I just filled up with fresh gas yesterday and added stabil to both tanks. I had a few people saying gas could be bad. Is there something else I should add to the new gas? I figured the stabil would help the gas.
 
Michael Mirra said:
if the engines rev in neutral then it sound to me like a transmission problem
Click to expand...
That could very well be the problem also. Starboard motor had new transmission in 2016.. I will check fluids.
 
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