looking for 100hp 10 mph
 

first actual forum question gents please help

the boat 96 baja 208 islander 61 gps 1.36 bravo drive 20p 4 blade with 310 454 carb gen v flat tappet engine

from what i can find online it has cast pistons at 8.0 to 1 and a whimpy cam but a steel gm crank 4 bolt block and the smaller gm forged rods

i already have a 1.36 x upper laying in the shop for it and got 12x16 tabs laying next to that all for the boat now my question to you fellows is should i put a 177 blower on it with about 4-5 lbs or try and find a 502 or something take out engine for it looking to spend least amount of money and keep turn key reliable and dock idle friendly so big cams and heads not really an option asking the local engine guys they seem very confidant it will hold 4 lbs especially if i do better springs in heads fact or fiction?:daz:

hands down teh best way to go :

1)sell the 454 in your boat for a good price.

2)take the cash, add it to the money that you woulda spent on the blower, blower carb, fuel system upgrades, etc.... and find a good 502 (efi, magnum, custom....whatever) there are some good deals on engines around these days...be patient and buy from a reputable source.

3) install it and buy the right prop. your at 70mph pretty easily

alot more dependability, longevity and room to improve later if you desire...for about the same money that you woulda spent upgrading a motor that wont live very long under harsh conditions created by supercharging. it MAY cost a tad more initially ( i repeat MAY)....but it will end up being cheaper and more reliable in the end....i promise.

JMO.....

i find it strange ,having a 1:36 on such a small engine....jmo

I don't see any mention of exhaust. If you do not have a good exhaust you can throw all the money you want at it and will not get the performance gains you are looking for.

Every performance marine builds requires a good exhaust system.

Judging from the thread title, you are looking for 100HP and 10MPH. Those two numbers typically don't go together.On a flat bottom boat, I'd expect to maybe pick up 5 MPH with a 100HP increase.

Put a blower on your 7.4L. You'll be just fine.

there's a buddy of mine running same lake with a 496 ho in a hammer and its similar boat style and size who is seeing 73-75 on gps and thats got roughly 130 more horse than mine only thing is he has a big 3 blade so its slow out of the hole and i romp on him to about 50 ish then he starts trimming drive and blows past me

and about the drive ratio it seems to be a popular numer on local baja here i am not to sure if they just got ordered that way or what thats all i know

When you are currently running 61, you should easily be in the 70-72 mph range with a 502. Many boats with that power, heavier and slower than yours, run 68-70 with the 502. The 502MPI is a better choice than boosting the 454. Less headaces and likely money saved down the road. I'd also say that resale is better too when time comes, the Merc 502MPI is a popular motor. BTW, if your motor is a non mag from '96 you have either the 7,4L 300 4B carb or the 7,4LX EFI 330. In '97 there was the 7,4L 300 4B carb, the 7,4LX 300 EFI and the 7,4LX MPI 330. The mags in '96 and '97 were the 454MAG 350 4B carb or the 454MAG MPI 385. The 7,4L MPI 310 showed up in '98,
To my knowledge and memory, all the non-mag 454's had cast internals all the way around, not ideal for boost. A 502 with a Baja labbed 23" M+ will make that thing really cool. Consider hydraulic steering:)

i was in correct on hp rating sorry AO it is a 300 310 makes me feel better:whistle: and speeking to multiple people ie local guys other oso members and this web page http://www.perfprotech.com/store/art...fications.aspx general conclusion on gen 5 block is 4 bolt main steel crank etc kinda middle ground for boost safe according to my engine guy he said real lazy timing and premo fuel should last he said the 525sc that he took down looked "overbuilt"

HHRRRUUH??????:party-smiley-004: Not really imo. Build for its intended use. The key word in high performance boating is "overbuild". Not trying to bash your motor guy at all, I don't know him. But that's a first for me.

61 mph? around 5000 rpm wot? do the exhaust like Big Jim said, and 23 prop and you will be around 67-8 with paid for 454. you need those 2 pieces first anyway before anything else will do what it is supposed to. what heads are they? peanut, or oval?

i picked up 2-3mph with dana's on my 7.4mpi in my hammer, that included spinning a 25 mirage plus after install, sell it and go with the 502, you will see real results

300 hp 454? that is a really conservative motor. they are rating small blocks at 300 these days. he might be hitting the rev limiter.

yeah it is at the bottom for sure but run great as long as you can leave it alone, 4400-4800 is the wot rpm range

No it's 4200-4600.

Butteboy has posted about the speed and prop in another thead. He tops out @ 4800 with a 20" 4 blade. That is 9% slip, just below the limiter. It could be a bit more 62ish with an M+ 21" @ 4600-4700 but with that setup 61 for the 300 hp @ 4800 is right on the money. An exhaust upgrade can give you a little as you said, but I'd suspect it to be from the weight saving.

67-68 with the 454 300? Never in a million years.

I agree with your engine guy. Put the blower on and have a ball with it. 30* all in timing and no more than 12af at wot. Nice thing to have would be inconnel exhaust valves and cometic head gaskets if you are going in to the engine. Another nice thing would be to switch your upper gears to 1.5s. You will really like the pop from that little blower and will see an easy 10mph with 5psi. No need to touch exhaust, heads or cam the blower will crutch it all up.

with the exception of thr forged rods[3/8 rodbolt]the internals are cast,but you can supercharge,just keep the boost at 3 lbs,many have done this with great success.

i have to respectfully dissagree, i stand corrected on the wot rpm, but i would see consistent 67-68 out of my 7.4 in my hammer, it was the 310 mpi version, not that it makes a diff, spinning a mirage plus 25 w/ dana exhaust and k&n filter, thats it, it was going through a 1.50 bravo, and yes it was gps speed w my garmin etrex

thanks for the support on the blower blue thunder and AO i agree somewhat with you on the overbuilt thing. i mean its not really a possible thing more so just wasted money up front and thats what he said " marine stuff costs so much because its got a warrentee not ment for people who know how to lift or tune or anything just pin them and get upset when it breaks" so i understand where he's coming from and we go back a bit he's helped with my 500 hp na 650 on button so i mean tunning i can do but not so much this boat stuff my safe idea is keep timing low and throw extra fuel at it

the ringer is my dad is the one who suggested second motor build so when i find another boat in 3-5 years at soonest gotta get life/ gf wife thing all square first:thankyouthankyou:

blown hammer your hull is realistically faster esp power for power thanks for the support

and i actually traded a blown up 4.6 ford for some 049 heads with new inconel ex valves TODAY

i agree,100 hp will not gain 10 mph,maybe 6,most likley 5.

anyone else have some input on the subject?

wrong button aparently when you hit enter on quick reply it submits it instad of dropping a line still new to this forum stuff

but on the subject at hand i mean it seems to be pretty split between building or finding a better engine and throwing blower on it and yes all you safety guy i am preparing for add on steering for the safety part of it wouldn want it to swap ends at speed

Prop change for TOP Speed
 

I would try a 3 blade Mirage 21"--23"? over the 4 blade. 100hp for 10 mph is a bit optimistic? You would need a very narrow beam light bow boat to get near 1mph per 10HP.

You are looking at 15HP to 20 Hp per MPH depending on hull beam and weight design. I would look into a better set of heads, matching cam, intake and carb which will put you in the mid 60s for sure. Keep the rpms in the 5200 rpm range the the cast pistons and cast crank will survive.

I also doubt the 502 putting most 25 to 28 ft boats into the 68 to 70 mph range more like in the mid 60s at best in my experience.

Having a 208 I bought new for 8 yrs mine came with a 1:50 bravo 1 and 23 Mirage same engine best I saw was 63 gps I could spin the mirage up to 5000 rpm. I will say that you want the tabs on because mine was a little squirrely at that speed on anything but flat water would start 2 chine walk

Butteboy I'm with the guys that suggested getting a complete motor to drop in.

BTW I have found this calculator to be very accurate IF you put in accurate current data and then calculate the constant. Keep in mind that your current engine is prop shaft hp.

Both of the boats I added hp was 11.6 hp per mph. There is no set number as hull design and current speed are important factors and the hp needed goes up as speed increases. It takes a lot more hp to fo from 80 to 90 than it does 60 to 70 even though they are both 10mph.

Bingo, right on.
Just remember the 502MPI 415 and 300 motor in question here are rated the same way. This motor is rated 300 hp the same way the 310, 330, 350, 365 and 385, 454s are. This particular boat is about 2 an-a-bit mph slower with the 7.4L 300 than with the 7.4LX EFI 330 hp. Call it prop shaft or call it crank shaft SAE J1349 hp, dosen't matter. And correct, you cannot generalize about how much hp 10 mph takes, your number of 11-12 from 61-71 is pretty spot on. Just look at how fast a 24OL or 25OL is with a 502MPI.

I mentioned the propshaft hp for the use of the calculator. As long as you use the same method every time no worries. Just don't want to "mix them" when running comparisons.

ok guys i thank you for all the info and opinions but :hitfan: unfortunately it has came to my attention that my hull cant handle ANY more power the starboard [right] stringer that the engine mounts to is soft and flexing cracking the fiberglass and twisting. according to a trusted local fiberglass repair guy the boat will be fine at 300-350 horse/ft pounds but doesnt suggest any more than that without replacing that stringer. so boats up for sale here locally:traurig001: but i am taking it as a sign to move into a little bigger and better boat gotta stay positive :angry-smiley-038:

at least patch it. layup 5 or 6 layers of heavy mat over the stringer. right one isn't as crucial as the left, since engine torque pulls up on the left one. but if the stringer is flexing, so is the hull...

Interesting, I gotta ask
 

I have a 1993 Baja Islander 454, I was told 330 hp when I bought it. With the age I'm guessing the 330 has relaxed to 300hp. I get 63mpg on the GPS, at 4600rpm. The exhaust is running thru the prop today, and running a mirage 23. I've been told labing the prop should get me 2 to 3 mph, thru hull exhaust 1 or 2 mph. GIL headers 1 to 2 mph. So 4 to 7 mph, I'm getting some of it used for $1400 which should bring the boat 67 to 70 mph. Seems like a great trade off, without jeopardizing reliability. I wondering what your opinions are about the suggested mpg gains I've been told? Also wondering how many horsepower you guys think I'll be running, the stern of the boat has a "330hp" sticker on it, thinking of replacing it.

l'd really appreciate your opinions!

The right prop and labbing it might get you 1-2mph, and all the exhaust mods. maybe 1 mph. I had a 1989 24' Sunsation with a 330 stock 454 Merc. and really didnt notice any difference going from thru hull from thru the prop. Im thinking 65 gps.

Switch to 150 ratio, YOUR LUGGING THE ENGINE WITH 1.36, IT WILL BE QUICKER WITH THE 150

Come on man! Johnny you need to be working on your boat instead on talking on here! Lol! You might need to come help me tomorrow. I'm struggling!