MILD THUNDER

iTrader: (3)

Something sounds way off to me. Nearly 600hp and only 60mph in that hull? I had a 241 Liberator that was prob quite a bit heavier and larger boat than a 235 Baja. That boat would run 70mph with 590hp single and a deep bravo.

Are you sure she's getting enough fuel at wot? AFRs of 13 is too lean for both safety and power.

What is your carbs list number and what jets in there ?

Budman II

iTrader: (1)

MT, yeah, a lean condition (or rich condition) is in the back of my mind, and I agree that there is almost no way I was making the dyno numbers to run those speeds.

In regards to jetting, I don't have the list number in front of me, but it is a Holley 800 straight off of an HP500. Jetting and dyno numbers are detailed in my dyno thread:

http://www.offshoreonly.com/forums/g...o-headers.html

From the thread:

"We started with the stock jetting that Holley puts in the list# for that carb - 72 primary and 87 secondary, with a 6.5 PV. First run was with this setup and 32* total timing. Went easy on it and only took it to 4700 RPM, and we got 484 HP and 540 ft/lbs. Next run we richened it up a little, and got 530 HP at 5400 RPM, similar torque numbers. We eventually got to 76 primary and 84 secondary on the jetting, same PV, and 34* total timing. At this point we were at about 565 HP and 580 ft/lbs. We tried an HVM Super Sucker 2"spacer on it, and it netted us a gain of about 10 HP. "

I believe 76 and 84 is where we left it.

In regards to the A/F ratio being too lean at 13+, that is what we saw with dyno headers. I asked about a correction factor when going to wet headers and mufflers in the boat, and got one response from lil red:

"if your using a wideband 02 in the exhaust if look for 13.1-13.3 a/f on the dyno and it should be 12.6-12.8 in the boat when you put your exhaust on etc."

He is the only one who addressed my question on the A/F ratio, and no one disagreed, so that is what I went with. So I am doubtful that I am seeing A/F numbers in the 13's on the water, but you never know. I sure wish there was a way to run a wideband with those Lightnings I have, or I would be all over it.

BTW, that damned avitar you are using is distracting the hell out of me. I always have to read your posts three times to absorb what you are saying because I'm looking over there waiting for her to take that thing the rest of the way off.

Drew555

I'm running a 21p laser on my 22' velocity. Turning 6000rpms and getting 75 no problem. I don't think a 23 would be to big for you. Is there a possibility you are over trimming the boat? If you have another prop to try I would start there

MILD THUNDER

iTrader: (3)

The problem could also be, in the fuel supply. Like too small a pump, too small a pickup in tank, etc. Is your fuel pressure holding enough fuel psi at wot?

When you guys dyno'ed, did you keep increasing JET until you saw a drop in peak HP? Or simply decide enough was enough because of the AFR readings?

I have found that the AFR readings on the dyno, can be misleading as far as power production. For example, ICDEDPPL's blown 540, made its best number, right at 11.5 AFR. Any leaner, it dropped power, any richer, it dropped a little.

My gut tells me, you had some more power in the engine with some more jet, even though you are N/A. Alot of guys have the mindset that lean means bigger power numbers. You really got to keep giving it what it wants, and let the dyno kinda show you whats up. The AFR is sort of a byproduct (to an extent).

If fuel pressure is holding steady, I think i'd begin throwing some jet at it. Especially since the temps are cooling down now, its not like its super hot humid summer air. Now is the time to dial her in while its good air.

MILD THUNDER

iTrader: (3)

Bud, lets think about this for a minute. You mentioned the carb was off a stock HP500 merc engine. That engine, made 470HP at the propshaft, and probably if you were to dyno one, on the dyno you did yours, it probably would have made around 520HP?

You are running a total jet diameter, of .366 when you add up all 4 jets. The HP500, had a total jet diameter of .488. So, you are running 25% less jet size (which is alot), but yet attempting to make almost 20% more horsepower (which is alot).

Just for conversation sake, take a 520HP, and drop 25% from that number. Thats 375HP. Which is almost dam near the speed you would get from that hull, with a 365HP 454 Mag.

Hardly scientific, just something to chew on though. It takes X amount of fuel, to make X amount of HP. Theres no getting around that.

Budman II

iTrader: (1)

MT, I haven't had a chance to check fuel pressure at speed. Thinking about mounting a GoPro aimed at it the next time I run it. We did not try to increase jet sizes in search of more power. We did try running more timing, and it didn't seem to like it. I think we went to 34*, then backed it down a little to 32*. My understanding is that the more efficient chambers on the AFR heads shouldn't need as much advance as the old cast iron heads do. I was mainly trying to get a good safe tune to avoid melting anything down - wasn't really interested in the biggest power number possible, but I know what you mean about going up in jet until the engine tells you that it doesn't like it.

I'll check the fuel pressure, and then look at adding some jet. Should I step up the secondaries first, or step up both primaries and secondaries at the same time?

ICDEDPPL

iTrader: (1)

Why can`t you run a 02 sensor in the lightnings? I had a set and ran 02`s for a long time without any issues.

I did not get richer in the boat, I was leaner and had to jet up from 84 to 91
Personally I wouldn`t go WOT on anything I didn`t know the AFRs on.
You could be way lean.




Notice the 02 bungs on top.

MILD THUNDER

iTrader: (3)

At this point we don't know the AFR's or even how the plugs look at cruise. Since you are running a Merc HP500 carb, I believe the same intake manifold?

I personally, always feel its best to start tuning being RICH, then work your way down. You don't want to be doing WOT passes repeatedly being lean.

You got 76/84 in those. If I remember right, that carb has different size boosters in the primary, or something like that. Stock jetting spread was 15 sizes. Which is weird, but thats what they came with. If it were my setup, I'd go 80P, and 94 S, and work from there.

Disregard my prior post somewhat. My morning math was off a bit. still was waiting for coffee to brew. The HP500 carb did not have 25% more jet diameter than what you are running. Definitly verify fuel pressure before anything.

First order of business is dialing the engine in. Props, drive height, and things of that nature, come second. I think at this point, the tune up is questionable, so need to verify all that first.

Budman II

iTrader: (1)

I was going by what others have experienced with their Lightnings. I think it was Endeaver who had a lot of issues with his sensors getting wet, especially at idle. I think his would live for a little while, but they would die a watery death as soon as he went back to idle. And mine have those funky divorced collectors, which complicates things. You may recall that I had to jump through all kinds of hoops with inner pipe extensions to keep mine from reverting. I guess I could try installing a set of bungs and see what happens, but I'm about out of money for this thing. Job front is getting shaky, wife is losing her job in December, so I can't throw much more money at it, unfortunately.

Guess I just live a charmed life when it comes to boats.

MILD THUNDER

iTrader: (3)

I had a problem on one of my engines 2 summers ago. One day the port engine would only hit 4500rpm and that was it. No stumble bog or hesitation. Just 4500 and that was it. Normally they turn 5500 no problem. Boost was there. Went back to dock, found fuel pump fitting on inlet side of pump loose. Fixed that went back out and reved right back to 5500

What are you running for fuel pump?