Why is that??

did you dyno the new engines ??? bet you are no where close to adding the power you are thinking..bigger heads/cam higher RPM intake all = higher RPM needed, all nil with loss of compression... bet you are making no more power at your usable RPM range at this point, drop the props down to get another 1000rpm or boost it.

IMO compression, timing and carb size are ALL limiting your hp, aside from possible distributor problem. Im currently dynoing a 8.48 548 na motor, going from 38 to 34 degrees timing cost 30 to 40 hp and i have slightly more compression, going from a unlimited tb (2200 cfm) to a 1000 cost 28 hp, advancing and retarding cam from 109 icl to 107 and 111 cost 20 hp fwiw. Now, your flow requirements ARENT as high as a 548 but i bet if you run a vacuum gauge off intake it will show carb restricting it, fwiw, smitty

Im getting great hp numbers from the 548 for what it is BUT torque w the big cam im using vs compression is down about 50 ft lbs everwhere from 3000 to 5300, whats your cranking compression ? Im seeing 145 psi

I will check compression tomorrow night after I get pertronix modules in. Is 1050 carb too big for me? Ill play with timing this weekend Let you know

Im following this because i have a buddy doing almost the exact same thing. Exept he came from a bone stock iron exaust manifold 454 mag ,that did run well. Also went from a bravo 1 to a xr.

These engine were originally cng emergecy water pump station crate engines lol. Needless to say i used the block and heads and tossed verything else

I would think 1050 carb would be good fit but im no carb expert

Gives me room ro grow. If they are too big duct tape can make them flow less. Jk

Hell, my 496's have 1050 dominators on 'em. Plugs look fine and it runs like a pack of muslims after the last goat on Earth.

Thats funny. What is your build

.

Here you go.

To answer your question why from a bit ago, its all about combination, the parts working well together, sometimes you throw stuff together with stuff laying around and runs better than it should...been lucky there myself, but many times goes the other way, your heads/cam/intake would work great @9.5, at this point the cam is letting what little compression you have right out the back door and the intake likes RPM and @ 5k that is not cutting it...

Here's an effective solution to the carb dilemma. I saw these pulled off an Eliminator that was converting to Whipples earlier this year at Young Performance Marine. Give Eddie a call and see if he still has them. I'm sure he can help you setup the proper timing/tuning. I know he'll even fly to you if a water tune is necessary. He rebuilt a carbed roots blower motor for us and it's tits.

10:1 496's, AFR 305 V2 heads, 454R intake with a 4500 flange, holley 1050's, crane 741's.

Theres a couple vids in the members online video section

Yes, too big.
An 850 would be a good choice.

Ran boat yesterday after changing pertronix modules. And adding 2 degrees timing. Total 36. Max rpm weekend before 5100 with 34 timing. Max rpm yesterday 4500?wtf. Also changed breakin oil before we went out. Broke it in with t4 rotella 15-40w with crane additive. Last weekend hot temps wot 65 and 20 idle. This weekend 65 wot and 5psi idle. Oil temp gauge is at remote filter before cooler. Temps ar wot are 240-250. Bearing clearance set at .0030 1-4 .0035 5. Rods .0029. Did i fry the oil or do i need a straight weight 40 or 50. Also we had extra 1000 pounds in boat this weekend. Not sure how much that would affect rpm

A lot! Need to be comparing apples to apples when making changes looking for improvement.

What oil do you have in it now?

5 psi I'd be removing the filter and cutting it open looking for things. Hope not, but ....

If motor is okay, check oil psi with mechanical gauge.

Checked into it today. Turns out my buddy pumped out the oil on the engines at 9 liters. Then put in 9 quarts. So we are at least 2 quarts over on the stock 8 qt mercruiser pans. Quite pissible a windage issue. From the bottom of the dipstick to the full mark is the same dustance past the full mark it is over on both engines

15-40 rotella t4. Will be switching to 20-50 vr1 synthetic soon

Ran the boat this weekend. Oil pressure is good. We switched from rotella to vr1. The previous issue was overfull by qt and half. Timing was set to 36 total with max rpm at 5200. Blowers are on the way. We tracked down a pair of b and m 250.

Curious to see new performance specs with the huffers on board. Your dominator should be a rocket this year when you get it dialed in. Perfect amount of power for that hull IMHO. I've always been a huge fan of the way that boat looks on the water.

I will keep you updated. Currently doung the glass work now. Had to shorten scoops and reshape.

I'd find it pretty damn coincidental, that BOTH engine builds, can only turn the same props to exactly 5100rpm wot.

We have a 9.6:1 vortec headed combo, and 230/236 cam, and a 8.3:1 EQ headed headed combo, with a 236/244 cam. Over a full point less static, different cams, different intakes, completely different heads, and they both make the EXACT same power at 5000/5100? 20-25hp is usually 100RPM in a boat.


I have seen aftermarket rev limiters, come in WAAAAY early and start killing power.

MGDOORS, how do the new engines feel? Do they feel stronger than the old ones say from 50mph to 70mph? What do you have for flame arrestors and hatch ventilation? What exhaust is on them?

Those 32's would crack 80mph with HP500's all day. I find it hard to believe, that even with 8.3:1 (hp500 was what, 8.75:1), better cylinder heads (both around 320cc), slightly bigger cam, 80cfm smaller carbs, both single plane intakes, would knock 8-10 plus mph off the boat. What altitude are you running at?

Altitude 3000. It runs stronger on top. Much stronger. Before after 4500 it would kinda take its time. Now gets there in a hurry. From what i understand my drives being 6 3/4 in the hole are hurting me. I have been running 26 bravo. They give bow steer bad unless trimmed pretty good runs flat but with rough ride. Never blowout ever. I have a set of labbed 27 mirage plus that dont take off worth a **** and blow out in rough. They were solid 6 miles an hour faster, boat felt light, rode smooth as silk in 3-4' whitecaps in havasu. Also they got to the top end Much Much faster. Like lightning. Im working with cutting edge now on some labbed 4 blade 30s that we are adding cup to the tip to air it out a bit. My buddy even said it looks like we have too much boat in the water.

Gil dry exhaust. Std hatch ventilation two on top two on sides one in rear. Was running kn 14x5. With blowers we are going to 3x12 bourbon

What kind of rpm gain can i expect from 5-6 boost on the blowers with same props

The fact the boat feels stronger on the top end, would make me think youre making more power. Naturally, you would expect a smaller cammed, smaller headed, higher compression, dual planed deal to run stronger low end, but if she's stronger in the 4000-5000 range, I'd imagine you picked up some power that should net a better top speed. If you told me it was a slug compared to the old engines acceleration and upper rpm range, then I'd think your combo may be why it isn't pulling the speed number.

Makes me think something else was going on. Rev limiters issue, hull/setup limitations, etc.

The blowers should wake it up for sure. If in fact you could only pull a 26 bravo to 5100, I think 30's might be a bit steep, even with the blowers, if you intend to turn 5500ish wot.

So put blowers on and ran it at 4.5 lbs boost. Gets up to speed like a pissed off honey badger. Problem is it hits wall at 5200. As did the last two builds. Im not accepting the whole not having enough power at this point. Have ran 25 std miarage 5200. 27mirage plus 5200. 26 bravo. 5200. All with mildly built 489 with vortec heads to blown 489 with eq320heads. Wtf is going on. Lifters or drive depth or distributors. Those are the only parts that are the same from build to build. Comp oem replacement lifters, pertronix dustributors licked at 30 timing, drive depth 6 3/4 directly below and 4 below pad. Do I nedd nose cones or something? Please advise

30 deg timing? I seriously doubt that is enough. I just dyno'd 2 blower motors and they liked 35 deg. They even fell way down on power at 32. Started losing power again at 37.

Inthink you may have missed the point. The boat has had 400hp engines, 500hp, now blown at roughly 620-650. All engines turned all props to 5200. I am quiet certain through research we have an ignition issue or lifters. Crane 741 cams with matched springs etc directly from crane. We do not have rev limiters set. Im going to start with coils as research tells me that the pertronix couls tend to fail. Btw I have a pair of labbed 32 on way and Im willing to bet the rpm will be same or close

I think we got this nailed down. Upon inspection and doind proper voltage load test I determined we have low voltage to coil and ignitor. Unloaded it shows 11.5 volts. Loaded 6.54 meaning we have a resistance wire somewhere. We wire relays in tonight and run it again Sunday with 32 labbed cutting edge props. Will keep you posted