I just did the first water test on my old baja 25 86, with trs new heads and cam and intake carb exc.
The test run did not run like it should have, to low of rpm.
I have a 454 pistons 100 dome new edelbrock oval marine heads (110 cc) Cam I .544 E .547 Du 226 236 112 cl
rpm intake. holly 800. trs new tranny. new stainless exh.
Before running steal heads and stock cam new pistons stock exhaust I was hitting 4350 rpm 49 mph with 23 mirage plus.
Now it runs 4500 rpm 50.5 mph
that just does not seem right?
I adjusted the timing back and forth trying to get the magic 600 rpm increase, no good.
help please I am very upset at this point.
any hints would be helpful,
It pulls great, rips right out of the hole.

no i did not degree the cam i called the special tech and asked about it they said I should not waist the time. comp cams

Your boat is acting very heavy, with a lot of prop slip. Here is my numerical prediction for your approximate setup. I have heard of boats with sealed off bilge pockets that have collected a bunch of water. If it is in the nose, you could be carrying around extra weight. Just an idea.

At any rate, you boat is behaving as though it were 5500 lb. I think your motor has a few more HP in it, but agree with Stuphen that you are overpropped. This is all based on a 330 hp 454. If your setup should be producing a lot more than that, you need to go through the motor setup and get it on a dyno.

You can run our simulation program with your actual parameters at www.speedboatperformance.com. Remember that BHP numbers are low due to atmospheric corrections.

Manufacturer: Baja

Model: 25

Length: 25 ft

Beam: 8 ft 0 in

Weight: 5500 lb

Deadrise Angle: 22 deg

Hull Depth: 5 ft

Number of Running Strakes: 2

Number of Transverse Ventilated Steps: 0

Hull does not have a keelpad

Boat has an open cockpit

Engine information:

Boat has 1 x 454 c.i. Normal engine installed

Engine Redline: 5000 RPM

Peak BHP is 350 BHP occuring at 4800 RPM

Peak Torque is 350 lb-ft occuring at 4400 RPM

Transmission information:

Boat has 1 x Borg-Warner 71C transmission

Drive information:

Boat has 1 x Merc TRS Drives Installed, with 1.5:1 gears

Propeller information:

Propeller: 3 bladed Mirage

Prop Diameter: 15.25 in

Prop Pitch: 23 in

Prop is set 24 inches behind, and 6 inches below the running surface

Environmental Conditions:

Boat is to be simulated operating in Salt Water, at 0 ft above msl, with an ambient air temperature of 80 degrees F

Program Completed

Computational Results
Your boat's computed performance is as follows:

SPEED(mph) ENGINE RPM REQ'D BHP AVAILABLE BHP PROP SLIP WETTED LENGTH(ft)
25.00 2756 136 220 38.41 16.55
26.00 2822 141 226 37.43 16.20
27.00 2889 147 231 36.51 15.87
28.00 2951 151 236 35.55 15.39
29.00 3019 157 242 34.73 15.11
30.00 3082 162 247 33.86 14.67
31.00 3150 168 252 33.12 14.43
32.00 3214 173 257 32.33 14.03
33.00 3277 178 262 31.57 13.65
34.00 3347 185 268 30.94 13.46
35.00 3411 190 272 30.24 13.11
36.00 3475 196 277 29.58 12.78
37.00 3545 203 282 29.04 12.62
38.00 3610 209 286 28.43 12.32
39.00 3675 215 291 27.84 12.03
40.00 3740 222 295 27.28 11.75
41.00 3811 230 299 26.83 11.63
42.00 3877 237 303 26.32 11.38
43.00 3942 244 307 25.82 11.13
44.00 4008 251 310 25.34 10.89
45.00 4074 259 314 24.88 10.66
46.00 4146 268 317 24.52 10.58
47.00 4212 276 320 24.10 10.37
48.00 4279 284 323 23.68 10.16
49.00 4345 292 325 23.29 9.968
50.00 4412 300 327 22.90 9.777
51.00 4479 309 329 22.54 9.594
52.00 4546 318 330 22.18 9.416
53.00 4613 327 332 21.84 9.245
53.52 4651 333 333 21.59 9.200

I agree with above folks...try a different wheel

you need to get those rpms up to realize any torque / hp that you have built...

borrow a 21 or 22 3b and see how it behaves when you get to your hp range...
I had a very similar problem with a 23 Nova my last boat ... MERC 420 cam, 800 holley, alum dual plane hirise, big heads and CMIs ...a real slug overpropped, got a 21 hydromotive or an old 21 merc lazer and brought it to the sweet spot of 5100 rpms and turned into a different boat- it came ALIVE.
Good luck

I also was running 1:32 gear set if that makes a difference in you application...point is get your RPMs up before you tear anything down by borrowing someones wheel

i have an old 21 pitch I can run. I will try that and see.
I mean it seems that there is no hope for this heavy boat.

Make sure the butterflies on the carb are opening all the way. What steel heads were you running? If they were rectangle port 990's or equivalent you may not have gained a whole lot with the ovals. Your cam will like 5000 - 5500 RPM. What is your compression ratio? I think the Edelbrock heads only have 110 cc combustion chambers which will make quite a bit more compression than the 118 cc stock stuff with the same piston and I see you are running some domes. I would hate to see you pound a piston out of it on your first or second trip!! Also motors with domed pistons like a little more timing, like 36 - 38, than motors with flat tops. I would hesitate going too high on the timing unless you know the compression.

Craig

Be careful with timing though, I'd invest in a spark retard system!! Its very hard to hear detenation over load exhaust and you'll burn up a piston or valve very quick under load.........

I noticed the timing is way off with the light . looks like 12:00 rather than 1:00... starts idles fine no detonation I have the motor hatch cover off.
What type of spark retarding system should I have ?
I have mark 4 thunder bolt 4, I looked for identifying numbers, none.
I am going to see if the timing is advancing or retarding @ 4000 rpm.
the old heads where not 990's they were just truck cheap heads.
I should have 9:3 1 or 9:5 1 with all checks.
I am going to test out now, thanks i will check back and let you know the results.

OK now I tried another prop and it changed the power band to high now.
and I spun a bearing.
so I have paid a small fortune on this project and now the lower end again.
I paid a so called reputable shop in mi. to do the lower end 2 times.
now on the third time I want no more problems ........help
suggestions ???? trade it in with a knock?
sell it out right with a knock?
work my tail off and fix it again??
who or what would you do???