370 Aft Cabin speed?

Sea Ray Mark

Sea Ray Mark

Member
Jun 11, 2008
583
Wildwood, N.J.
Boat Info
1999 33 Sundancer

2005 Mercury Amanzi
40 HP Super Dinghy

1997 Wellcraft 190 CCF
Engines
Mercruiser 310 HP MPI
Does anyone have some real world knowledge of what kind of speed I should expect from a 1997 with 380hp Horizons? I just bought this boat and ran it from the place of purchase to my winter yard in Jersey which was an 8 1/2 hr trip. Started out at 3700 rpm doing about 14 - 14.5 kts because it seemed like that's what it needed to get it to plane off. As we got into some area's with less current against us we were hitting some blazing speeds in the mid 15 kt range. At the end of the trip I had to push it up to 4000 rpm at about 18 - 19 kts to get out of the Delaware bay before the sun set. This boat is absolutely empty of gear and water so the only weight factor I had was fuel. I also had no canvas on it so the wind resistance was even less then normal and the bottom is clean. I don't like to cruise big blocks above 3600 rpm but maybe I have to with this boat. Pretty cheap to replace if I blow them up but I don't like to abuse my motors. Any thoughts or feedback would be appreciated. Thanks, Mark
 
I wish I could be more helpful. I have the same hull configuration from the rub rail down, but have diesel engines with bigger props. Fully loaded my sweet spot for cruising is 18 knots and I need about 14 knots to get on plane. Full throttle, no water or gear and half fuel; she'll make nearly 27 knots downhill.

If you do end up doing a re-power, I would highly recommend going to diesel. That's a lot of boat for gas engines IMHO.
 
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Congrats on the new boat Mark.

A few years back, two neighbors each had 37/38 ACMYs. One was a 2001 380 SeaRay and the other a 2000 3750 Cruisers. Both boats had the 7.4 380HP Horizon motors. Back then, I had my 1998 330DA. The point I'm making is that both of those boats were able to cruise right along with me running at 22 knots +/-. Now, they did have to juice up the throttles a bit, and from memory, I think they ran those motors up close to 4000 RPMs. 14-15 kts, to me, seems way to slow...heck, even ol' pokey in his 1988 bridge boat cruises faster than that.
 
We have the 370AC w/380 Horizons. It is not a fast boat. I'm not sure it has a sweet spot. I never run above 3300 rpms very long. We get 10 mph @ 2600. Ours has 24" x 22p props. I have no idea if they are correct but that's what on it. It had 95 hrs when we purchased her. Ours is just not a fast boat. We always wanted to go on some of the MM runs along the Gulf but have not because we just can't keep up. We would arrive when everyone else is ready to move on. Maybe it's OK to run these engines in the mid 3000's. Ours doesn't seem to be able to the 4000's.
I remember at one point with the wind behind us we did see 21mph. Very smooth bay that day, but have never seen her do it again. Never wanted to have to run her that hard.
 
osd9 said:
Congrats on the new boat Mark.

A few years back, two neighbors each had 37/38 ACMYs. One was a 2001 380 SeaRay and the other a 2000 3750 Cruisers. Both boats had the 7.4 380HP Horizon motors. Back then, I had my 1998 330DA. The point I'm making is that both of those boats were able to cruise right along with me running at 22 knots +/-. Now, they did have to juice up the throttles a bit, and from memory, I think they ran those motors up close to 4000 RPMs. 14-15 kts, to me, seems way to slow...heck, even ol' pokey in his 1988 bridge boat cruises faster than that.
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Dom, I did see 20knots a couple of times at 4000 rpm trying to escape the bay but again the boat is pretty empty. I think once I load it down with beer and put the canvas up it's going to suffer. I obviously need to have the props checked but I was curious to see what I should expect after it's all set up correctly. Hopefully some other 370AC owners will chime in but I realize this is a slow boat with gas motors. Thanks, Mark
 
Skeeto, thanks for the input. I had a 370DB 1992 with gas motors at one time and that was a 16 -18 knot cruise. I thought the aft cabin would have the same hull as my DA and my DB but it's actually different. The DA and DB that I had were both 12' 7" beam but my AC is 14' 3". Didn't think Sea Ray would go through the trouble of making a different hull for this one model but they did. I can really tell the difference with the space between the engines. Makes it real nice to work on them. Mark
 
You should be getting a lot better than that.

I know I have a completely different boat, but not that much different in terms of power, size, and weight.

I'm turning 20-23 mph at 3300 rpm and top out at 31/32 mph at top rated rpm which is 4400 on my 454 Crusaders (350 HP).

There is a guy across the dock from me with a 370 SR Aft Cabin and he seems to stay right with me on plane and cruises that way the majority of the time.

Is the bottom clean? Props free of any growth? You will need to do some investigating because that performance would be pretty dissapointing.
 
Mark: you may have a dirty bottom. You should be going faster than that at 3700RPM. I'll let the other 370/380 guys answer this question but I'd bet you should be moving closer to 20mph at that RPM.

And for the record, Mr. Nunzie, my boat is an '89 and at 3700RPM I'd be blazing along at around 24mph. I CAN, but I choose NOT TO! ;-)
 
Mark - sent you a PM but your box is full.
 
What's the hurry? Besides, I don't want to blow a piston out the side of the block. You really have to baby these old classics.
 
Carver370 said:
You should be getting a lot better than that.

I know I have a completely different boat, but not that much different in terms of power, size, and weight.

I'm turning 20-23 mph at 3300 rpm and top out at 31/32 mph at top rated rpm which is 4400 on my 454 Crusaders (350 HP).

There is a guy across the dock from me with a 370 SR Aft Cabin and he seems to stay right with me on plane and cruises that way the majority of the time.

Is the bottom clean? Props free of any growth? You will need to do some investigating because that performance would be pretty dissapointing.
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Carver 370, the bottom is clean. It was short hauled and power washed for survey so I know that's not the problem. I guess I have to get the props done to take them out of the equation and then make sure the tachometers are correct. I assume the techs are close because the fuel burn was about 37 gph which seems to be close to what I would expect at 3700 rpm. I would be happy with a cruise speed of 20 - 23 mph with this boat. Just need to figure out the problem. Thanks, Mark
 
I've got a 370AC with the Horizons. I've had it up to 35mph loaded. Normally 8-10 mph at 1200-1500 rpm. She revs pretty good for a big girl. But we normally just cruise along at 7-10 mph. The throttles all the way forward is just showing off to guests, to see the size of the hole she leaves behind.....
 
TheBells13 said:
I've got a 370AC with the Horizons. I've had it up to 35mph loaded. Normally 8-10 mph at 1200-1500 rpm. She revs pretty good for a big girl. But we normally just cruise along at 7-10 mph. The throttles all the way forward is just showing off to guests, to see the size of the hole she leaves behind.....
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Thanks for the info. Do you know what speed it will do in the 3400rpm range?
 
Wow! I can't get my fat-bottomed girl much over 31mph, loaded or unloaded!
 
Rick, yes it did. But a lot of these aft cabins had fireplaces right? Lol Mark
 
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