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krb260

Member
Joined
Feb 27, 2007
RO Number
25341
Messages
25
I have a 2004 searay 260 da with the 350 mag. Since new i can only ashive 4600 rpm at wot. This is the same loaded or empty. When i questioned the dealer they told me this was ok. I believe this boat does not hold on plane well and i have to run it at 4000 rpms to maintain plane all to often. It has the smallest props available 20p with a 2.20:1 ratio. I have heard the are putting 2.43:1 ratios in now(STARTING IN 2005), AND REFITTING 2004 models on warranty issues. Anyone with info please as I cannot bear running this boat another season like this.
 
Well, I think the 350 mag engine is supposed to be in the 4600 - 5000 RPM range at WOT, so you're in that range, albeit the low end. Cruising (staying on plane) should be a little lower than 4000, though, maybe like about 3200-3500? I would check the prop, make sure it is clean and true, no nicks, etc. You might be able to test drive a smaller prop (sometimes the dealers will let you test them out), like maybe a 19" or 18" pitch, but that seems kinda low.
 
A prop shop just looked at them and siad they where perfect and wouldn't advise touching them as i wanted them to tweak them to get 3 or 4 hundred rpms. the 20p is the smallest pitch available for the bravo III . yes it is 4600-5000 and mercruiser wants to see it 4900-5000.
 
Well, then, you might be underpowered. Replace the engine with a big block.
 
blouderback whats the ratio and props on your larson it seems to be about the same boat
 
quote:
Originally posted by krb260

It came fitted with factory installed bennett trim tabs

Click to expand...


Not trying to be a smart ass but do you use them? If not go to the Bennett web site for an excellent tutorial on how to properly use trim tabs. Not sure if they still have it but they offered an interactive program you could download and practice using tabs.

Also trimming the outdrive is very important as well.
 
I useually trim tho outdrive all the way in and use the tabs to the point where handling is compromised
 
yes thats the indication to me as i am almost always trying to keep it down. It seems to be spinning the props and not going.
 
Sounds to me that bigger tabs or more throw on the tabs is needed. Can you move any weight forward?
 
once on plan shouldn't you move the outdrive up somewhat then use your tabs abit ? The 30-32 searay will have 2 options, 1 for I/O and one for IB. When I was looking at searays last year the sales guy liked the I/O's for performace due to the ability to move the prop angle with the I/O once on plan. I don't think running with I/O full down is the answer to make max rpm's
 
I have tried loading everything forward doesnt seem to help much, it also doesnt matter loaded or empty
 
krb,

I have 28" pitch props with a 2.20:1 ratio. My boat is much lighter than yours, though. Is yours a 260 Sundancer? My Larson is only about 3400lbs dry, your 260 Sundander is almost twice that at 7500lbs dry, and your engine is only 80hp more.
 
Other than underpowered, the answer will be in the trim. Underway you should have both trim tab down somw what, and the prop somewhat up, the exact trim would have to be arrived at by trial and error. I would start out with tabs up, prop down, adjust both tabs down until speed starts to decrease, then adjust prop up, keep adjusting until you get max speed, WOT should follow the speed.
 
The only other thing I can think of is timing not advancing properly.
 
FIRST...What drive do you have and what diameter are your prop(s)?

My first guess(with a BII) would a minimum 20" diameter prop for 20" pitch with a 2.2 gear ratio but I would have expected a 24+ pitch with a 2.2 gear ratio.

There are RO's with BIII with more info on their prop size.

I would also get that tach checked!!!
 
Good point on getting the tach checked. What is your WOT and slowest planing speed?
 
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