cant get over 50mph why why
 

Well I am new 2 this it s my 2nd boat I used to have a 27 ft sunray cabin crusier 350 stock . It hit 35 around heqvy boat at least 4200lbs . Nowi got a 21 ft baja hammer bought it with a cracked block on a 350 .so I sent it out had it done up heads done extreme marien cam5800 red line oversized 30.ooo elderblock 600cfm holly fuelpump thunderbolt ignition . No matter what I do I cant get over 50mph have tred changing props from ss to aluminum 17p to 23 p o and it was 1.47 gear ratio . A place out here told me 2 get gears to 1.32 so I did 1600$$$ later now I need a 17p to get to 48mph with a 21p I have a hard time geting out the water once out hits 50mph the place that did the motor work tells me I have min very min350hp I thought I would be runing a 21 p and doing at least 62+mph .and ft is a alpha 1 gen2 I had one pearson adjust carb and timing . Now someone else telling me maybe timeing chain or a exaust problem maybe air restriction.... can anybody help me I cant afford the marien shops no more at 95$ A HOUR just my gears coast me 960$ pluse 557$ for them to install

thats strange i had a 22 footer that did 59 consistently on gps with a 300 magnum smallblock and a 17 pitch prop. i think it could have used a 21 pitch too. It had a 1.5 ratio alpha with a snapped off skeg lol

i would think your not actually making 350 hp. Do a leak down on the motor and get the specs on the heads and bottom end.

What is the motor reving out to under load??

And the shop that said you had to regear your drive to get speed out of a 21' boat... don't ever go back there. ( I hope they are not the ones who built your motor)(

with the 1.5 and a 21p three blade Im guessing you should be doing 50 at least 1000 rpm below your 5800 rpm redline.

17p?? wholly hell man, how tight were you winding that thing????

Ya pretty much I around 4800rpm and no I had a diff place bulid motor there been doing it in the same shop for 45 years I am at about 5 gs in moter 1600 in ft and no father ahead . ( and just feel like theres no hope or money left could it be my manifolds air restriction. ...

first thing: did you check if your speedometer gauge is accurate compared to a gps?

had a 454 hammer that ran 65-67

1.5 with 21 pitch at 5000 should put you around 60 mph no doubt

if speedometer is accurate something is wrong with the engine

did you tested it on a dyno before install?

stock speedometers are sometimes close to accurate, but really shouldn't be depended on. download an app and see what gps says.

Ya I used gps on phone spedos bang on no I didnt put dyno test but u hear the cam u feel the power I mean with the 1.47 and 21p I geting like 45rpm can t get more in less I drop pitch and then all I get is more rpms and way better hole shot . I can be plaind in 4 sec almost and it flys up 2 50mph in no time I was going on glass water 50mph I go in 2 foot waves and against current and still do 50mph np cant figer it out I s cheak oil s fine no meatl no gas nada . Plugs r good never any problems with starting or anything running smoothly beautiful sound. I was looking for a place for dyno off the prop .I didnt want to pull motor again . I might not have anychoice but I kinda belive the motor place 45 years I dnt think hes screwing ppl thats all they do is machine motors tmr I put more specs offf the billl he gave me or some paper that came I belive with the cam

I will post it up tmr the compression I belive when the built it was 215 each around I have to cheak tmr I marked down somethings he told me and I did compression test like 3 weeks ago and it was all in the upper 185170 I will find ppw ty

if your running fine its probably okay im just anal and i do a leak down on everything, its the only way to know for sure.

My Baja 212 islander with 454 MPI would do between 65-67mph with a 3 blade 21 pitch bravo. That was with a BB so I don't think the small block will push it much past 55-60 unless it is built and has some torque.

Are you trimming up? Sorry but there was not reason to change gear ratio, and you were better off with 1.47. Where is the timing set? That 600 cfm carb should be fine out of the box so I hope they only adjusted idle mixture.

I will find out about timeing degrees where its at to day and yes tried triming I could be at 45 mph and hit the gas and it jumps 2 50mph np

And out of four ppl 2 tell me adjust timing while boats moveing and these r guys from a marien and 2 told me they adjust at 3000 rpms on land I so fed up

Set initial at 10 at idle, total should be in low 30s. That will be close.

You want total timing to be around 34*. That's a sweet spot for a SBC. Also, what are the numbers on your Thunderbolt module, should read V8-22 or such.

Call Zul

Anybody can build a low to mid 300hp 350 and make a 20ft performance boat run 60mph.

That's the cruel thing with this whole thread.

If you can use better english typing - i'm not that picky but you are giving me a migrain - maybe we can have a better conversation.

#1 - those gears are bullchit. They just took power away from you. Did you run the new motor build with the old gears ? And if so, what happened.

#2 - comp makes many different extreme marine cams. Please list exactly what cam they used.

#3 - what heads ? If factory, which style or year ?

#4 - which intake manifold

#5 - what pistons did they put in your new motor. Manufacturer and part# is needed. Not a description of flat top/dome/or etc as that can lie to you as far as compression.

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Don't !

Many modules keep advancing past 3 grand. Some modules don't stop till 4200rpm. I think one goes to 4500rpm.

Ya I did it ran like 4300rpm and was doing 50mph with a 21p the rest I am going to dig out papers I have and be back soon thanks and srry was half a slep when I stared on this form.

So, your new motor in front of a 1.5 geared Alpha, ran 4300WOT at 50mph with a 21P ?

A 21P what kind of prop ?

BTW: Awaiting what kind of prop, that's basically what a stock 260HP 350 will do with that gear and prop. or little better.

comp cams part /12-240-4 cs xm 270h-12 grindcs xm270h 12 valve lift int .480 exauust .489 duration .06 tappet lift 270 int open 286 exaust close lobe lift .3200 int lobe lift .3260 exaust lobe separation 112.0 i dont know about the piston but i know there flat head piston eldebrock carb 600 cfm eldebrock performer intake holly fuel pump with all these modification still cant get over 50 mph why please help me

Should not have made a gear change, but regardless your not making power.

Who put it together? I ran into something like this with a friends boat. He did a cam swap and it was installed retarded. So even with giving advanced ignition timing it ran like a dog. Also, did you do an exhaust upgrade? Just wondering.

Do you have a fuel pressure gauge on it? I have also seen engines run out of steam because the fuel pump was getting weak at WOT.

My migrain is back.

Please, I wanna help - I beg you - normal communication please.

About your cam - with 350cid's you really need 9.5:1 or preferably more to make it work well.
Also, stock exhaust will have a hard time with that cam.

The XM270H has 226, 236 at .050" / 112LSA and if installed to Comp's specs, only installed on a 110ICL.
It'd s lot of cam for an other wise mild build.

Too much cam for what you probably have, but have yet to answer those other pertinent questions.

You need to answer exactly what else you have for us to further help.

Impossible if you don't know what you have for us to see if it's an engine build issue or a possible tuning or engine health issue.

It would be like me asking everyone why I haven't scored Pamela Anderson yet.

Because you have respect for your dick and a desire not to get a big ole antibiotic shot in the ass??

Hell no ! :hitit:

.554/.557 On that cam....I think an exhaust upgrade is a must. That thing can't breath

Not on the XM 270H for small block. It's under .500"

Anyway, cam is way wrong for a mild 350 build.

Your right, sorry. I looked up xm270h and I found a big block cam with that grind # on the comp website.

x 1,000,000.

OP, please mix in some punctuation marks, use paragraphs and semi-complete sentences at the least.

I'm not a grammar Nazi, but holy jeebus.

Pull motor and dyno it. All questions will be answered then. If it makes no power then it will be apparent right away. (Cam timing off a tooth? That would be my guess. If it makes power on dyno you either have a fuel, ignition, or drive line issue in the boat. Have you double checked if you are getting wide open throttle?

Whe I bought this motor I put it I boat stock I was hitting 35 40mph I pulled it out sent it in to a engin rebuild shop had oversized 300 small cam and put a elderblock 600cfm on top of the elderblock performer with a holy fuel pump manual was a combo kit from summit racing. Put it in boat and was hiting 50mph I wanted faster so pulled it back out took motor back told the guy need more power he says I was around the 200 hp so we talked told me 250mag was 325 and stuff so I told him want more then that so he did the heads and put a cam in it and polished my air in take . Tells me now he 100% sure its min very min hp now is 350 say more like 375 to 400 but for his on sack says 350 for sure . Now speeds under 50mph I can feel the power it s has but yet still not past 50mph and marina told me gear ratio in foot so went 1.47 to a 1.32 not its only in the 40s mph only diff is I push less throttle but cant get out the hole and 21 prop I have bought 3 props this year 17 19 aluminum 21 23 stainless steel . Have tred them all.. I will be going to c the guy for the motor again to day ask for a specs on motor but I am pretty sure it fine I been thinking it might be air restriction in manifolds or mufflers . I have talked 2 like 4 mechanics and they all tell me diff one say I need . Avedaced timming . Cheak throttle cable carb opens all the way runing 94 oct have timming done at 40 50mph on water other says on trailer at 3000rpm . I just dnt know I thinking cuting out baffles in mufflers . Can andone give me a idea am about to sell boat amd get a camper lol.

Does the boat have 27 layers of bottom paint?? A major hook? If not you need to tell the engine builder to stick with briggs and stratten..

Was this a car engine builder or a boat engine builder?

Are you Jim Darrs son by any chance?

jim,

i thnk u u ned a b3 drve puut a 5bade prp on wth a 3 bld shld ht 60-65 thn

hop this helps

No paintt lol they build all motor s performance, car ,truck s ,boats. They been buissness 45years very well recommended by 3 ppl . The shop very busy I been there a lot and dnt see ppl complaining at all can it be muffler with air restriction

No I see lots of ppl using alpha 1s yes it might fall apart after but shd be working anyway

If I have to spend more effort reading than the person does typing, it makes me feal like I care more than you do, and that's not right.

Sorry bud. I'm not being an azzhole.

If your english is schit because of texting, wait till you can hit a real computer and respond clearly.

Of all people, i can't believe I'm having trouble with your language.

Later.

It is simple, the engine is not making the power. I have a 21ft Larson, 5.0L efi making 270HP. I run 55 at 4900RPM with a 21 3 blade.

sel bot and git kamper


SB please pass the Tylenol