New Owner to 2900 scr

[DFD L30]

We recently traded in our faithful 2300 sc for a 2900scr. We love our new cruiser however I'm concerned with rpm vs. mph. I have found our best cruising speed to be about 23 - 24 mph but the engine is turning 4000 - 4100 rpm. Is this normal for this model equipped with a single 6.2L B3 ???

[seapuppy]

Hi DFD....I had the 2700 SCR with 6.2/b3 drive...my boat ran all the time at 4k rpm and we'd be cruising at about 30-32 mph depending on tides and wind...so..if yours is wound up that tight...you are probably under propped..what drive and prop do you have...your wot should be 5280rpm if your running an mpi system on that 6.2ltr engine...if it's carbed then 4400-4800 rpm is wot....since your running a b3 drive ..I'm assuming your props are 22p - 24p props...if thats so..then you should top out at about 42-44mph....so..to investigate further...how is the bottom of the boat doing??...how much stuff and gear do you have onboard....is there water in the bilge...lots???...when was the last tune up???...is the flame arrestor clean??....
are you getting wot from the shifter??ie...when you push the throttle all the way open..is the throttle plate open all the way??..
those are a few things off the top of my head to check..


SP

[ss3964spd]

I found this from a test of the 2600 SE with the 6.2:

"As with most boats in this class, moving through rough water can be bumpy, but when conditions are ideal, a top speed of 40.7 mph can be reached from the 320 horsepower engine option. A brisk cruise speed of 30 mph can also be obtained with the big engine turning at 4000 rpm while delivering just over 2 miles to the gallon."

Your 2900 with a single 6.2 is significantly heavier than the 2600 SE so I'm not convinced you'll see anything over 40 MPH.

Dan

[DFD L30]

Our boat will achieve 5100 rpm @wot with a speed of 37-38 mph in a mild chop. Engine is efi and tuned up this spring. not much gear on board but the bottom is painted. I'm not sure of the prop pitch but if I go to a different prop, won't I sacrifice planing out easier for less rpm@ cruising speed???

[seapuppy]

well.your 2900 is close to my 2700 by about a foot...mine was the wide beam...I topped out wot at 42.5mph gps measured....now..since your saying your engine and drive is almost identical...maxum engineers their boats to about 42mph...almost every one of thier boats tops out at about 42mph.....smaller boats obviously run quite a bit faster....
now since you have ruled out the engine as it was tuned..you didn't say you were running in chop...any boat will have to slow down in chop...so...lets try another route...is the hull bottom clean...no growing critters..cuz if you have any growth on it..it will slow down markedly....

now with the prop...if you have a a lower pitched prop..you get on plane faster but sacrifice top end...your wot is higher...the 6.2ltr engine has a cut out or rev limiter set to 5280rpm....so..you should be able to run right up to the rev limiter......your cruise speed should be right around 30mph at 4k rpm...28mph should be at about 3800rpm....if your not getting that speed in smooth waters...then your not trimmed right or your under pitched.......or you hull is dirty....that's the only thing that can stop the boat from performing...

SP

[ss3964spd]

Do you trim the drive up after getting on plane?

Mine picks up about 200 - 300 RPM and 1-2 MPH when running at WOT when I trim the drive up.

Dan

[DFD L30]

I do trim the drive up properly however I am still learning how to use the trim tabs. Should they be used for anything other than to correct listing left or right, lowering the bow in a chop, or getting up on plane when the boat is carrying more weight?

[seapuppy]

use the trim tabs to level the boat due to loads but also during startup...put the tabs down...hit the throttle and then start bumping them up till you get the right angle on the bow...if your in chop...lower the bow to punch thru the waves or chop...slow down some...or if in calm water..just retract them all the way and bump the drive up till you feel it free up....

SP