500efi help
 

I bought the boat last fall. The engine was gone thru just before I purchased it. Cast heads were changed to aluminum. Before the overhaul, previous owner always had blow by in the valves and said the engine compartment was always oily. He added a puke tank to try and solve the problem. Still have some blow by and no oil going to the puke tank. Today I noticed what looked like oil coming up the dipstick tube. The engine only runs about 48-4900 rpm with a top speed of 71 with perfect conditions. Previous owner said it ran about 5400 rpm with a top speed of 77. Anybody have any thoughts of what could be going on with my engine?

What hull? Is this a 22 foot boat? That's a stout speed for an HP500EFI single engine boat.
Are you sure the tachometer is right?

288 Sunsation, engine is pushing approximately 560 hp according to previous owner.

To get this out of the way and don't take offense if not, is this your first boat ?

Yes this is my first performance boat. No offense taken, i know some but by no means an expert!

Don't worry, you'll know more than you ever wanted to about oil cooler line sizes, why electric fuel pumps suck in boats, and how replacing a trim tab leads to adding a mega blower to your engine soon enough.

Where do you live? Was it winterized properly? Any water in the oil? The standard brain trust question will be have you done a compression test yet?

A 288 if my memory serves me right ran 72 with a 496 ho
560 should in fact be close to...75-77 like stated.
Did you do a compression test? I would!

Northern MI, it was winterized properly, I have not done a compression test yet. Engine seems to run strong, no misfiring, always starts good, just seems to be lacking something. I'm assuming the stock tach on the dash is correct but could be off a little?

What psi should I be seeing while checking compression?

How much have you played with trim, tabs, and a GPS ?

I usually put the tabs down 3/4 of the way while getting on plane then I bring them all the way up when on plane and adjust my out drive trim up to gain optimum ride and speed in calm water. When it's rougher conditions I run the tabs down a touch at a time till the bow comes down some and gives me the best ride.

I built up a 500 efi and fine tuned it on the water in a steppedd hull 27 fountain, boat ran 74 to 76 when it was stock depending on how much fuel and passengers, runs 77 to 80 ish now depending on load. I havent seen many single engine 500 efi boats run upper 70's, not sure if a 288 is a "fast"hull or not but my first question is what do you have for a prop, if you tell me 26 non labbed four blade theres your prob, takes a good 600+ hp to turn a 26 on a v hull and at that usually needs to be labbed. So you either have a fkd up tune, hurt motor or too tall of prop if boat wont rpm (aside from putting extra batterys and passengers in cabin/bow or something blatantly obvious), Smitty

Is that a GPS speedometer you are getting your numbers from?

Have you ruled out a bad batch of gas? Checked the fuel separator for water? I'm just focusing on the performance before the oil purging. Other than blow-by around the rings why would a crankcase pressurize so much?

Fwiw - I'm just a shade tree hack with the wrenches myself just here to learn.

I don't intend to ruin your day however I would recommend doing a compression check. We had the same issue on a 500 efi that was just rebuilt prior to us buying it, motor ran great but would occasionally push a little oil out dipstick. Did a compression check and number 6 cylinder was down just a bit. Pulled motor and had a chipped piston and small portion of ring missing. Id start with a compression check, that will point you in right direction.

Since i started flowing and cleaning injectors this is a re-ocurring story, 15+ year efi motors, never had injectors flowed, tested or cleaned, 1 low flowing injector kills a cylinder, lots of oil blowing out breathers because of excessive blowby on a hurt piston

It does have a 26p prop non labbed.

Do a Compression Test and a Leak Down Test..... You have to find out if its healthy , if its blowing oil out the dipstick , its either to much oil in the pan , or excessive blowby from a bad cylinder.
Also pull the oil filler cap off the valve cover, if its puffing pressure out like a steam train , you've got problems.

Well you read my previous comment on that before you even told me you had that prop I haven't seen a 500efi turn a 26 non labbed in a big single V to where it needs to be like 52 or 5400 you need a labbed 26 prop at a minimum and even then you'll probably only turn 5200 but that's part of why it's only turning 4800, if you're coming too hot boat I see you're in Michigan I can bring a 26 lab for you to try

I can also tell you if your motor has a stock ECU at 4800 it only gets 28 degrees of timing and jumps to 36 degrees by 5200 maybe even at 5000 I don't remember but I can tell you if you don't hit that 5000 RPMs and jump to the 36 degrees at 100 map the boat will never pull

A 26p is a pretty big wheel to spin. I know a lot of 272 folks have trouble spinning a 25p with anything under ~625 HP.

My 272 would only spin a 26 non labbed 5200 at 72/73 with 645 ish gross dyno hp, needed a 26 labbed. A customer has a aetco 580hp 540 in s single checkmate, wont even turn a 26 LABBED past 4800, fwiw, your dead on. A modded 500 efi unless its super strong and in a light, stepped hull ) like a 27 fountain isnt doing it either. Fwiw, Smitty

Some boats (Like Formula) use 1.65 gears. Thus why bigger props than others of the same size.

But yeh, my experience for most , say, 26-30 boats with 1,5 gears end up with around 24 Bravos with 500-550hp or some more. That's why used 24 Bravo's don't stay for sale long. Very popular prop and size.

My 272 Islander with about 500 Dyno HP spins a labbed Mirage plus 25p with 1:65 gears up to an indicated 5600 and 64 mph. Even if he has 1:65 gears 26p is huge.

I didn't know about the graduated timing steps. If it can't spin high enough to advance the timing then that's certainly problematic.

Stock 500 efi timing table is a joke, its at 27 or 28 degrees thru 4800 then jumps to 35.9 suddenly in 200 rpms (at a 100 map)