Speed and RPM on 2001 380 aft Cabin Gas

J

Jeff S

New Member
Aug 11, 2011
7
Arizona
Boat Info
2001 Sea Ray 380 Aft Cabin
Engines
Twin merc 454 380 HP
All,
I am in the process of buying a 2001 380 AC but, have a concern. I am new to larger boats and during the sea trial today could only get the boat to about 13 knots and 2900 RPM at full throttle. The gas engines have about 160 hrs on them. Does this sound normal?? Thanks for any input.
 
Last edited:
I can't speak directly to the 454 max RPM but it sounds low. Our 8.1's are about 4,200 RPM near max.
Perhaps someone with 454's will add some input to this thread.
 
The 7.4 Mercruiser should turn up in the 4300-4400 rpm area, depending upon what year and model engine you have. THe AC's with gas power are never very fast, but you should see something like 18 kts at cruise. So,

Houston: We have a problem..............
 
Absolutely not. Regardless of how fast you're going they should be in the 4,000 to 4,200 range. When's the last bottom job it had? Did it vibrate?

Something's not right.
 
Bottom looks OK but, it is coming out of the water today. No vibration. The current owner(Original) and dealer that delivered the boat say it has been this way from day one. It will just be a lake boat in AZ and they say the props need to be re-pitched to get more speed/rpm???? Thanks for the help so far!!
 
That means it has 160 overloaded engines hours on it. That must burn like 50 gph.
 
Turtlesboat said:
That means it has 160 overloaded engines hours on it. That must burn like 50 gph.
Click to expand...

I was thinking the same thing. One more reason to not take hour meters very seriously.

Jeff, have you confirmed that your trim tabs are working? Friends of mine have a Silverton 352, which is a very similar boat. Their tabs have failed several times, and without tabs, that boat acts just like yours.
 
Trim tabs do work. I'll check the idle speed today also.

Again thanks to everyone for your input.
 
I also seriously doubt that Sea Ray Shipped a boat that did not perform to spec.
 
It sounds like there is some sort of a fuel injection problem. If both engines only get 2900 rpm and are synched Ill bet its a computer or wiring issue. 2900 RPM would probably be about 13 knots with that boat but the RPM's should go at least another 1500 RPM.
 
While I have more info. We pulled the boat out today, barnicles(sp?) were fairly heavy on trim tabs, intakes, rudders and some on the prop. The rest of the hull was clean. I had the entire bottom pressure washed. At idle 3.6 mph. The clean up gained about 100rpm to 3000-3100. Top speed 15 mph. When in neutral the engines will run at 4,500 rpm. The surveyor thinks the props need to be changed (pitch/diameter). Accourding to Sea Ray they are correct?? They are pulling all specs and going to send them to a prop company to get their input. Any other thoughts?
 
Jeff, I read your original post earlier, and I just asked one of my buddies who just happens to have the exact same boat what his numbers were. He said he runs 29mph right at 5000rpm. Hope this helps.
 
Kreole kid,
That helps a lot, thanks. Does he have any idea what props he is running?
 
http://www.yachtsurvey.com/boatreviews/SeaRay370ac.htm Be careful an engine that has low hours is worst than an engine with high hours. A 10 year old boat with a 160 hours let see average 16 hours a year, riser and manifolds shines on the out side if not change rusted inside, seals dried up, A siting engine is bad news. Sounds like he was afraid to take the boat out make sure you can handle the aft cabin, it is alot different than a sedan or a express.
 
Arizona has Zebra Mussels, not barnacles. My 370 AC is on Lake Powell. Michigan Wheel advises the I need to change my 24x22 prop to a 24x18 prop. They say there is a 13% loss of power at my elevation.
Anton on board Ya'a'teeh III
 
If the current owner can't get it operating to spec (by any way other than just drastically changing the props), I'd pass on the boat. If he's run it like that for 160 hours, those motors could be pretty ragged out. Those props would be somewhere between 5-8" off in pitch. There is no way Sea Ray would ship it like that, unless the boat has picked up 15,000 pounds since it was delivered!
 
We have a 1998 370AC and we have had the boat to 21mph. But that was with low fuel and low water and only 2 people on board and all the canvas down. The wind screen alone is like a four by ten board through the air. Also it was before the boss put all here and the grandkids stuff on board. We run the stock 24x22 props and have had them checked and tuned. Also remember the shafts on these boats at just 1.5" which I think is a little small for the weight. We also unhooked the throttle sinc because it caused more problems than help. We sinc by sound. Also you might have tachs that are off. Our surveyor said both of ours were off.
We bought ours 18 months ago and it had 95 hours on the Horizons and had never been registered with Mercruiser. Sitting boats with low hours are appealing and I went for it. In the future if I run into another opportunity like that one I would still do the deal/////But I would allow a maybe 5k to bring the boat up on maintainence.
These are not fast boats. They have a planning hull but getting them up burns more fuel than it's worth for just a nice cocktail cruise. We cruise ours at anywhere from 1600 rpms to 2600 which moves us between 8.5 mph and maybe 14 depending greatly on the wind and the seas and we enjoy the ride. My opinion is these boats should be run like a trawler. There wide beams and tunnells with that much weight is just a go fast solution. If you are basing your purchase on speed than a AC might not be your best solution, however if you want the style and room and an enjoyable ride that doesn't smoke your credit card than these are good solutions. They have lots of storage and ours has the washer dryer with additional storage. By the time you fill all the tanks and have all your stuff on board along with family and/or friends you have added several thousand pounds to a boat with the Merc's that is already under powered. We have the high horse power option on ours which is the fuel injected 380hp version of Horizons. Maybe it's just me but I will not run these engines at high RPMs. It runs up your per hour costs, makes the ride rough (at least in the gulf) and it is loud at high rpms. Ac's are like condo's on the water and are to be relaxing. We all want boats that are cared for and maintained and running them at 4/5 rpms I don't think is what we would want to purchase. The thought that they are supposed to do that is great and in an emergency I would of course burn them up trying to get help but just to take it out and run them that hard is not in our program for having a well taken care of and nurtured boat. These are good boats and we enjoy ours but I would be cautous to compare apple with watermelons. These are of course just our opinions!
 
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