Ebay Ed

my new to me hp 500 efi has some issues 7 cylinders with 70% or more leakage at bare minimum the heads have to come off. should i 1 just do what i need to get it going ? 2 go thru the entire engine ( dont really have the money to do this ), 3 go thru the entire engine and bump it up a little while in there ( really dont really have the money to do this ) but i heard that these engines really come alive with a cam and reflash ( well easy to get 600 hp doing this ) i want reliablity turn key every weekend so i can waste gas and all i have for an outdrive is a stock bravo 1 so i know if i bump the engine up i will probably kiss it good bye

Thunderstruck27

Well...I like to spend other people's money so I say bump it up! LOL Really, when it comes time to open mine up I will be upgrading too...and I'm on a tight budget also. Lots of luck to you no matter how you go.
TS27

88Fount33

Problem with just doing enough to get going may have you doing most of the items over again if something lets go.

During the leakage test, what was the component of leakage going into the crankcase, that is, are the rings shot? Getting any piston slap going on.

How's the oil pressure:
Cold Vs Hot?
Cold at speed Vs. Hot at Speed?
Cold at Idle Vs. Hot at Idle?
If your pressure is somwhat stable, then perhaps your bearings are still within tolerance, if not then...B.O.A.Ten Thousand.

Boats eat cubic dollars, modified engine boats eat cubic dollars X ten. And NO ONE will give you anything close to $.20 on the $1.00 for your modified eninge from a KNOWN and well respected engine source. Do it yourself and get about $.01 for every dollar spent. I just dumped MAJOR $$ into repowering, of which I will see $0.00 if I had to sell. Boating is more fun than dumping Benjamins into a barrel and setting them on fire, unless you are freezing to death.

Ted G

iTrader: (1)

Sounds like you may have trashed the valves due to leaky headers, love me some CMI's So I would get those checked. The bottom end on these engines seems to be pretty bulletproof so you may be able to get away with just the heads. That said I just went through the bottom and heads on one of mine for $625 in machine work $400 on the heads and $225 to tank it, hone it, replace cam bearings and freeze plugs. So doing a once over can be fairly cheap and is good insurance. By the time I get bearings, rings and a set of lifters I will be less than $1500 in. Don't know if I'd run 600 hp through a standard Bravo, but the boat's not too heavy so if you take it easy....

Raylar

I am an engine builder and as such I am going to ask here on the forum that when OSO'ers like yourself always try to give enough fact and information about your needs and issues so that others here on the forum can help by giving you hopefully good council and advise.
When you are describing the condition of an engine you need to give anyone you are asking for sound mechanical advise good basic descriptions and detail.
First, how many hours on this engine that has now developed a leaking cylinder pressure problem?
Oil pressures, cold and hot as previous poster asked?
7 out of 8 cylinders with that high of leakage in a new to you 500EFI indicates an engine survey was not done at the time of purchase which could have prevented this position you are in now.
In any event , yes with that type of leakage you are definitely into internal engine work with heads and springs and possibly some valves and seats a most likely outcome. However if the engine is a high hour engine with no previous rebuild you could possibly get into a full engine rebuild, which on this Merc Racing engine will be fairly expensive.

As for a cam and program change to add by themselves big power to this engine I would disagree in that the camshaft Merc Racing uses in this engine is a good sized camshaft for the stock heads, compression, and cubic inches of this engine. If you have to do major work to this engine then if you need a big power increase you should consider a heads, camshaft and program upgrade package like those offered by Eddie Young, Atteco Engines or others that have proven package upgrades that can be combined with either your stock base engine or a rebuild engine block.

Best Regards,
Ray @ Raylar

Griff

I would most likely do a full stock rebuild. You won't get 600hp with just a cam and reflash. That might get you to 530hp. You would need a better set of heads to get 600hp.

Ebay Ed

ok thanks guys just so you know the guy i bought it off of never ran it he bought it to install and never got around to it i nor he has ever ran this so no idea on the oil pressure i honestly do not beleive he misrepresented it to me he was only going off of what he was told when he bought it he has read these threads i have about this and called me to see if i though he screwed me or if i wanted my money back i am sure we will be able to work something out but i think i may just go ahead and go thru the entire engine that way i know what i have and how much time is on it

blue thunder

Squirt some oil in the low cylinders and see if the leak % improves. If they don't improve (indicating valves are at fault), refresh the top end and pressure test the headers. You can always change this plan if you get in there and the cylinders are shot or you find a lot of metal laying around.

Ebay Ed

i was told it sounds like there is more air going thru the valves so we are just going to pull the heads and have a look i guess

blue thunder

Make sure you pressure test the exhaust like Ted said above, it is highly possible that is the root cause. Do an OSO search on those pipes leaking and you will see.