Baja 454 mpi breaks up at WOT

[butchmotors]

I am new to this forum .I recently bought a 96 baja islander 208.It has a 454 mpi with about 330 hours on it. I rented a slip in the genesee river, so finally no more trailering. I ran about 3 full tanks of gas through it with no problems ,itl do about 73 on gps with 3 people on it. recently itl start breaking up around 65mph and sounds like its running out of fuel. I heard a problem with water in the fuel tank so I replaced the filter/water seperator.It didnt seem to help. now im noticing went I hit waves its also cutting out just for a split second,and seems to be getting worse . The guy I bought the boat from said last year he ran ethanol by accident and it started acting up .He said he put some treatment in the gas and it took care of the problem.I dont want to add anything without assurance ,and I stay away from fuel with ethanol.I personally think the fuel pump is givving up. Please any help would be greatly appreciated .

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT

Im starting to think its a cut off switch of some kind thats giving me the misfiring when I hit waves. Im imagining its a mercury switch or of that sort,,,does anyone have any knowledge on these switches?

 

[Philster]

Re: Baja 454 mpi breaks up at WOT

How big is this boat? 73 sounds very wrong. Maybe the GPS readout at WOT and Max operating engine speed headed down current would lead you to believe you are hitting 73.

To clip 70 in that rig you are pushing it to the extreme limit of it operating range. Are we talking bone stock engine here?

Need:
Engine specs.
Boat size/weight
Prop size, blades, type

You ask 100 performance boaters and 99 are going to say it's a 60-65 MPH boat. Makes me curious about the engine, any mods and other wild cards and variables not known here. And, presto, she runs into trouble above 65.

Call me skeptical.

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT

Its about twenty one overall, 3500lbs, some stainless prop looks like a stock quicksilver. The guy I bought it from said it has a set of upgraded heads on it.Honestly it looks bone stock to me but it does do over seventy on gps and is definetly flat bottomed and overpowered.

 

[rodbolt]

Re: Baja 454 mpi breaks up at WOT

check fuel rail pressure at the problem RPM,best I recall its about 45PSI minimum but the service manual will tell you.
if rail pressure is good replace the screens in the injectors or send them out to an injector shop such as flagship marine in punta gorda FL.
no cutout switchs.

 

[Philster]

Re: Baja 454 mpi breaks up at WOT

Upgraded heads?

Hmmm.... some intake head and/or exhaust header mods require ECM reprogramming (if possible).

Ya got hiccups at WOT. This would be where the ECM is in unchartered territory, when flows are at rates not programmed precisely into the chip.

Simple engine mods with engine computers are sometimes not so simple.

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT

I appreciate the advice Rodbolt, I will check pressure when I get a minute..so really no tip over switch? I guess thats what the wristband is for! I have a marine mechanic for a neighbor who mentioned those injectores ,he said they rust over the winter.

 

[Silvertip]

Re: Baja 454 mpi breaks up at WOT

Hitting a rev limiter perhaps? Breakup when hitting waves would not point to a fuel pump but could point to a fuel pickup issue. Such as sediment or gunk in the tank causing a restriction at high speed. Pulling the dip tube may be worth a look. Valve float at high rpm (although we don't have a WOT rpm number at 73 MPH). Ignition breakup at high rpm due to almost anything in the system.

 

[Philster]

Re: Baja 454 mpi breaks up at WOT

Do check back, please, when the problem is rectified as a courtesy to those who want to know (I don't guess it's the injectors).

I feel they'd reveal problems under strong acceleration.

.

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT

I definetly will let you guys know what it is when I find the problem. im not hittin the redline, I think over seventy is right around 4600-4700rpm. Im guessing the next thing il do is full tuneup , the wires look new but who knows. Im also goin to check fuell pressure and my pickup . I know on anything forced induction ignition can be sensitive. I build and own turbo cars and bikes and they eat up plugs ..This is my first big block anything ,and honestly it seems like old technology but the whole marine application everything throse a wrech in the works.again I greatly appreciate the help.

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT

Hitting a rev limiter perhaps? Breakup when hitting waves would not point to a fuel pump but could point to a fuel pickup issue. Such as sediment or gunk in the tank causing a restriction at high speed. Pulling the dip tube may be worth a look. Valve float at high rpm (although we don't have a WOT rpm number at 73 MPH). Ignition breakup at high rpm due to almost anything in the system.

When im hitting waves and it cuts out, itl do it at allmost any speed/rpm,,but its ben rainy in rochester so the second I get time to check it out Il post

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT



I puting my money on this being all my problems.The plugs and wires looked pretty new,but when I took the cap off it looked like two tablespoons of seasoned salt was under the rotor..Most oxidization ive ever seen in a cap,doesent make sense about jumping waves and cutting out,but im sure this stuff was just flying around in the cap. the electrodes in the cap have at least 1/4 inch of junk on them...The place I bought the cap said when you winterize the boat ,unscrew the cap to let any moisture out till next season,,makes sense..again I appreciate all the advice.I took it for a ride yesterday, seems to run great and runs alot smoother

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT

Ive ben out a handfull of times since I did a tuneup, as far as wot,no more problems. when im hitting waves i can still hear it cutting out for a split second. It seems that the less gas I have the more frequent it becomes,wich makes me think its a pickup problem.My neighbor at my slip is a marine mechanic,he said check all the wire looms make sure ther not pulling on any connections.I made sure ther all secured. I know thers one kill switch on my outdrive res .I think il bypass that for a few mins and try again

 

[HT32BSX115]

Re: Baja 454 mpi breaks up at WOT

I definetly will let you guys know what it is when I find the problem. im not hittin the redline, I think over seventy is right around 4600-4700rpm.

That is almost ALWAYS the REV limiter. The rev limiter calculates the RPM directly so the TACH could easily be off (high) at the upper range by a couple hundred RPM. The Rev Limiter would still detect the overspeed.


You won't know for sure until you try a known (different) tachometer.


What is your drive ratio (probably 1.50:1?)

What's the prop pitch?


Cheers,


Rick

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT

That is almost ALWAYS the REV limiter. The rev limiter calculates the RPM directly so the TACH could easily be off (high) at the upper range by a couple hundred RPM. The Rev Limiter would still detect the overspeed.


You won't know for sure until you try a known (different) tachometer.


What is your drive ratio (probably 1.50:1?)

What's the prop pitch?


Cheers,


Rick

It cant be the redline because I can be gong 25mph on flat water for ten mins with no problem hit a wave and split second power loss. Yesterday I finally unplugged the outdrive res overfill cutoff switch with no luck. Its really startin to drive me nuts!!

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT

Finally figured out the problem,,That little cutoff switch for the wristband. I checked it before with my fluke and it tested out good.The other day it was choppy and started cutting out real bad ,,then stalled and no restart till I togled with that stupid switch. I still have to order a switch ,for now I bypassed it and It runs awsome In any waves, I want to say I appreciate all the advice.

 

[butchmotors]

Re: Baja 454 mpi breaks up at WOT

Now that thats sorted out.Im looking to make this boat a little faster. Is a higher pitched prop going to take to much from the low end

 

[Bondo]

Re: Baja 454 mpi breaks up at WOT

Now that thats sorted out.Im looking to make this boat a little faster. Is a higher pitched prop going to take to much from the low end

Ayuh,.... Time to take This question to the Prop Forum....