1st post some questions (272 islander)
 

Hey all,
I'm new here so hi!!
Last year I purchased a new to me 1997 272 islander with a 496 ho (it's a 2006 model repower)
I have a few questions concerning speed.
I have only been able to achieve 61 mph full tank almost empty 4 passengers or by myself it always seems to top out at 61 mph.
From what I understand it should go maybe mid 60's some saying upper 60's
Anyway I have the seastrainer (I think that's what it's called) on the bottom of the boat for the 496 fresh water intake.
I also have a 23 pitch mercury mirage stainless prop and thru hull exhaust. (Engine is factory)
At the speed of 61 mph (GPS speed) my tach shows it spinning at 5200 rpms so I don't hold her there too long.
The engine has 500 hours on it, the hull has no scratches or gouges but the zinc plates on my outdrive are pretty corroded.
Also the prop has a slight gouge on one of the blades and I don't know what gear ratio I have.
One other thing...my trim gauge don't work I'm sure because my trim sender/limiters are shot. (I just ordered a set to replace them before I get on the water this year)
Anyways is my speeds waay off or am I about in the ballpark with where I should be?
Oh yeah this is at about 650' sea level.
Thanks

Welcome to OSO!! 61 is probably a little low...possibly the boat was repowered, but they didn't change the prop? Are you sure the tach is right? I thought a 496 had a 5150 rpm rev limiter.....anyway the boat should be propped to run 4900-5000 rpm...might give a 25 mirage prop a try.

Hi,
Good question about the tach being correct.
With no certainty I cannot say it is but it sure sounds like its over 5k
I would also assume the prop is the original prop but again don't really know.
I have also thought about stepping up to the 25 prop to get my rpms back down to 4800 but again without knowing if my tach is correct I'm not sure.
Anyway thanks for the reply.

I would think that 61 is about right. Hook'em is doing a little better than that (mid 60's) with a strong (but stock) 502 and a mirage 25. If you really are pulling 5200 then definitely put some more prop on it. Unless you are just looking for speed, try a 4 blade prop (Bravo 1 22 pitch or Rev 4 23 pitch). I have enjoyed the 4 blades on our 252.

Are you saying that you have a separate water pickup mounted on the hull (through the hull?) and are not drawing cooling water in from the outdrive? Post a picture.

Dan

That is correct Dan, I have a freshwater pickup under the hull toward the rear.

+1 on the 23 rev 4

I had tried a 21 rev 4 on my 25ol and it liked it!! Good right out the box. I hit 61 bouncing on rev with my 454 mag, so the ho should push a 23 easily. Also the 21 walked right out the water with only 2500 rpms which was nice.. didnt have any friends with the 23.... :(

Tom, is it possible that you're over trimming (with out a working gauge)? The M+ 23 blows out very easy in stock form. I would think you'd be able to hear/feel when the prop loses grip. With the proper work, that is the "right prop".

With 425 ponies the 272 SHOULD run well up into the mid/high60's.

I have heard of 2-4 MPH scrubbed from a poorly set up water pickup. Just throwing out ideas there.

If the 500 hr motor is tired (down on HP) then the combo of high slip at the wheel (non labbed M+) and extra drag on the bottom I could see where 61 is about all shes got.

Yeah, I think it's very possible and highly likely that without my trim gauge I am over trimming it.
I am going by ear as I trim and being as I bought this boat last year and its new to me I am not used to hearing what it should be like.
My other boat was a 17' caravelle bowrider with a wimpy 4 banger and the trim gauge worked but I found it quite easy to tell when I over trimmed it as I can hear the engine start over revving and it wanted to start porpoising.
This boat doesn't porpoise and I haven't heard the engine go to an overrev as I'm trimming it but....like I say it's new to me so maybe I'm not hearing it correctly.
Anyway here shortly I'm going to have new trim sender/limiters installed so maybe I can eliminate that.
I really feel she should do mid to maybe high 60's myself but maybe I'm hoping instead. Lol
Thx

I had a 275 Baja Performance with 496 HO, Bravo X drive, through transom pick up. 23P bravo prop. Touched 67 on GPS on a cool day with light fuel and no passengers. Ran about 63 with passengers and full fuel.

True, but he's got the open bow version which will run a few mph slower with the same power.

I'm going with the tach being off (maybe) but the speed isn't far off.