Slow Larson :(

[KnotConnected]

How fast should a '94 Cabrio 280 (10' beam) pushed by a single 454 with 2 -4 light people in it cruise at trimmed up and running on flat water? I can top at MAYBE 28, and cruise at 23, which seems slow. I've heard from people that it's a big boat with a big beam and the 454 is right where it should be, and I've heard from other people with similar sized boats and single 454's they they can top at 40 and cruise in the mid 30s.

If it SHOULD be running faster, any ideas how to get'er there?


Thanks as always!

 

[redneck joe]

'similar size' is very subjective.

Buddy had a 28' Sea Ray with a less than 10' beam and his was about same as yours. Could be other issues such as prop, extra carried on/stored item weight, etc.

 

[Alumarine]

What are your rpm's at WOT?
Are you trimming it out a bit?
Do you have trim tabs?

 

[smokeonthewater]

Sounds spot on to me.... My same size boat makes it into the upper 40's but I have twins....
You have 330? hp and I have 520 hp

 

[smokeonthewater]

Btw mine can also make 100 gallons of fuel disappear in just over half the time yours takes....

Don't sweat it you have a cruiser so cruise...

I'd have no problem if my twin V-8's were V-6's.

 

[KnotConnected]

WOT is ~4300 RPM , idle at 600RPM (warm) and I cruise around 3800RPM to take it easy on the 'ol girl. Big floppy trim tabs, but I keep'm up and mainly trim with the drive. I've also got a pair of 22 pitch'd props on the B3, which I think could be part of the issue?

 

[smokeonthewater]

IMHO you don't HAVE a problem except for wanting a faster boat...
Your speed and rpm's are right where they should be.

 

[RGrew176]

How fast should a '94 Cabrio 280 (10' beam) pushed by a single 454 with 2 -4 light people in it cruise at trimmed up and running on flat water? I can top at MAYBE 28, and cruise at 23, which seems slow. I've heard from people that it's a big boat with a big beam and the 454 is right where it should be, and I've heard from other people with similar sized boats and single 454's they they can top at 40 and cruise in the mid 30s.

If it SHOULD be running faster, any ideas how to get'er there?


Thanks as always!

That sure does seem slow to me. I had a 1996 Bayliner 2855 Ciera with the 7.4 (454) 300 HP Bravo III combo that topped out at 51 MPH according to my GPS. It was probably a bit lighter as it only had a 9' 7" beam but that boat sure did fly. I did rack store therefore I did not have any bottom paint on the hull and I kept the hull waxed so the comparison is definitely not an apples to apples comparison. I would think that your boat should at least top out in the mid 40's and cruise in the lower to mid 30's.

 

[tpenfield]

Engine RPM seem fine 22 pitch props are probably right for that boat . . . so . . . let's go with the boat is now too heavy theory. Water retention maybe?

How long have you owned this boat? did it ever go fast for you?

 

[KnotConnected]

I've only had it since the end of 2012's season, and it's my first so it has taken me a long time to get comfortable with it, and I've never really paid attention to its top speed until last year. I generally run it without any onboard water, and don't have any significantly cargo. It's always been this fast far as I know.

Aren't the 22p props designed for a quick out-of-the-hole, and lower top speed? Could I go with 24p or could that cause issues with acceleration?

 

[tpenfield]

Since your engine RPM is within the spec of a 7.4 at 4300 rpm, there seems to be a decent match of engine to prop. BTW props for a B3 are pricey, so not high on the list for messing with it. If you go to 24 pitch, your RPM's will probably go down to 3900.

Best to do a process of elimination. . . Starting with the more likely first.

 

[airdvr1227]

Your WOT rpm's are right. If you change pitch you're going to change RPM. Sure seems like that boat should be a bit faster...at least into the high 30's or low 40's. Need to have her weighed.

 

[KnotConnected]

So if everything else is in spec, is it entirely possible that compared to my buddy's 28' x 10' SeaRay with a 454 that's much quicker, the Larson just has a lot more fiberglass & thicker, heavier core? I'm totally fine with accepting the fact that I'll have to take my time on every trip we take, I just want to make sure that it's not under performing as a result of some engine or configuration problem.

 

[tpenfield]

So if everything else is in spec, is it entirely possible that compared to my buddy's 28' x 10' SeaRay with a 454 that's much quicker, the Larson just has a lot more fiberglass & thicker, heavier core? I'm totally fine with accepting the fact that I'll have to take my time on every trip we take, I just want to make sure that it's not under performing as a result of some engine or configuration problem.

. . . or it is full of water or something else bad. I don't think a Larson is going to be heavier than a lot of similar boats on its own. I'd be looking for signs of water in the structure, foam, etc. It is one of the things to be confirmed or eliminated.

 

[smokeonthewater]

It's always a good idea to check timing on the engine... Both at idle and up to wot.... Never know could be a little retarded.

 

[KnotConnected]

Timing was checked at time of purchase, but never hurts to check'er again. I'm going to plug my ears and scream *lalala* at the waterlog possibility. I've put WAY too much time and money into this boat to have any structural issues. Also, I've just scheduled an appointment to have the structure checked. :-\ Other than having it checked by a professional with a magical water sensing gizmo, is there anything I can do to get an idea of the structure might have water in it?

 

[redneck joe]

weigh it.

 

[JoLin]

It's always a good idea to check timing on the engine... Both at idle and up to wot.... Never know could be a little retarded.

Too true. Bought my boat last spring. It ran fine so I didn't do much to it during the season. At the very end of last season I did my first high speed run and found to my surprise that while the port engine would reach 4700+ rpm (range is 4400-4800) the starboard engine would only reach 4400. Before spring launch I did a COMPLETE tuneup and found the starboard engine's timing retarded by a whopping 8 degrees. I'll note that the engine ran normally in all respects, for all of last year. I had no starting or running problems with it at all.

Since I launched this season it seems like a new boat- much peppier and fuel consumption is down noticeably, too.

My .02

 

[KnotConnected]

Thanks everyone! I searched craigslist for other 1994 Cabrios with 454s to track down other owners, and asked them if theirs performed better. Consensus is that the thing *should* top out around 40. I'll look into timing and weight.

 

[shrew]

What you're describing is pretty spot on. The max rpm range for the 454 is 4400-4800. 22.5 pitch prop on a 28 ft boat with a 10 ft. beam, a single 454 and a B3 drive is about right. The numbers and specs are right in line with what I'm getting for the same size and setup. What needs to be tuned is your expectations.