BBlades - awesome test program!

If what I'm reading on this internet thing is correct that ignition comes with a 5k rev limiter chip in it, and a ~200 rpm error on a 20 year old oem tach wouldn't be unreasonable. Both props seemed to top aout at 4800, and when I would keep trimming out it would go to 5k and slow down, so I'd drop the drive until it hooked back up at around 4800. That's what I have my fingers crossed for at the moment. I can't make it back to the boat storage though for another day or so to verify though.

Bah. I couldn't wait and went down to the boat and checked the ignition. It's nothing fancy, but it's not likely to be the limiting factor.



I'm still getting 22% slip. I guess that maybe I've just got a turd of a boat. *Shrug*

Fwiw - I did find a bent area on the drive "plate"(?) if that can make any difference.

Sounds like you are on the right track Rooster. From my experience the R4 23 is a lot of prop. Sounds like it is performing about as expected except for the slip. 22% is still a lot at those speeds. Sounds like the old M+ has some issues so at least you've got that behind you. It is odd that you pulled the same rpm with both props. I believe (but am not 100% confident) that your rev limiter will be a "hard" limiter. When it engages it interrupts ignition and will result in a miss or complete cutout. You will know it when you run into the limit. It is not a soft limiter like many of the newer ones that start retarding timing and the whole engine just sort of goes limp.

FWIW I had a Faria tack as original equipment and it started giving very false readings. Not so bad at first but progressively worse. A tack is not your problem but if providing bad information it may be clouding the issue.

RiReuter - the Islanders are a little heavier than their closed bow cousins. The problem may be particularly bad in the 272 Islanders. While I have not been able to compare one directly to our 252, from pictures it appears that the bow sections are the same and the cockpit section is much bigger on the 272. The 272 has a big U shaped rear seat whereas the 252 series and the 272 Boss barely have room for a bench. Assuming that the 272 B/I series uses the same hull and that this would fix the firewall location, the only way to get that extra cockpit room would be to move the forward end of the cockpit (and windshield) forward. This would also make sense from a production point as the deck mold on the 272 would be common with the 252 until aft of the window glass. If this is the case then not only might the Islander be a little heavier, but the driver and co driver would be moved farther forward than on the closed bow 272 which would be a significant weight shift.

Rooster, you should still be well over 60. Don't quit looking yet!

Thanks BajaDan!

I *think* the Holley Red fuel pump may be an issue with 500hp. It's wierd how both props tached out about the same, but the heavier prop accelerated much quicker. The red fuel pump is good for 67gph @ 7psi and 96psi free flow. The last 1/3 of throttle does nothing when planed out. On the previous motor with a flat cam and broken lifter (600hp) it actually bogged when the secondaries opened.

Yep, I like the four blades. I've been running a Bravo 1 24 p prop for years. It's my favorite. It spins easier than the Rev 4 23 p. The M+ is a couple of mph faster than the B1 though.

If you are starving for fuel that could explain the behavior you are seeing. I have read a lot about the Holly pumps and none of it has been good. It seems that most of the time they just quit though. 67 gph should be twice what you need.

http://www.offshoreonly.com/classifi...o55371-en.html

Here is a link to a 272 Islander showing the cockpit and large U shaped rear seat. I must say from the pictures this looks to be a nice boat. When we were looking we could never find a 272 Islander to look at. At anything less than wide open throttle, that cockpit would be really nice to have. Rooster I am assuming that yours is similar?

I should also point out that an Islander makes a great camera boat. One day we were chasing some others and doing some film work with a 175 lb (guesstimate on my part) guy right up front. That only took a couple of mph off our top end believe it or not. Baja's seem to carry weight forward pretty well, at least at the speeds we are discussing now.

Yep - that boat is identical to mine straight down to the dash layout. I absolutely love the boat, and we have enjoyed the open bow a lot - it's my favorite place to ride. Other than that missing 10mph I wouldn't change a thing, lol. It's just small enough for the lakes/wake boarding and just big enough for the bay.

Yes sir, a bent up cavitation plate could be causing..........cavitation. Not even sure HTF that would happen. That's hard to tell much from the pix but looks shady Rooster.

I asked Brad at BBlades about it and his take on it was that it's pretty much out of the water at speed as it's the upper plate, but I can still see how it would screw things up. It looks like someone pulled the drive out and dropped it forward onto the lip. Would it be safe to take a mapp has torch and see if I can bump that up a bit straighter?

So here's a shot of the spark plug after about 20 hours of use. This was after about 15 minutes of idling to the dock and a pretty decent gunning (but nothing ridiculous) to get it on the trailer.

The drives on our boats are really deep. I bet it has a fair amount of drag and could be adding to the problem.

I know they can weld a damaged skeg but I really have no idea about heating and bending on it. I would have thought it would break.