timing curve for omc 225hp

[lahnlubba]

i have just replaced the distributor in my 1973 sea ray w/ 5.7 litre 225hp engine. I put in a later model HEI from a camaro, mainly to do away with the points setup. It starts and idles great, but seems to really lack the top end it used to have , Can anyone tell me what sort of timing curve boat motors have? it seems to idle really nice and slow and evenly now, with no stalling when docking so i am very happy with the swap i'd just like a little more top end <br />(tops out @ 3600), the timing is at 4btdc.<br />thanks to all.<br />nick

 

[Bondo]

Re: timing curve for omc 225hp

Timing Should be Full Advance Before 3000rpms... <br />Bump up the base timing to 7 or 8*....<br />You Should be spinning 4400rpms at WOT...

 

[Trent]

Re: timing curve for omc 225hp

I here a BOOM comming! <br /><br />Automotive parts do not belong on a boat! You need a Marine specific distributor for saftey!

 

[lahnlubba]

Re: timing curve for omc 225hp

thanks for your reply bondo!!,when does the "curve start? right off idle? or does it come in all in a rush @ around 2-3000? full advance being 36 deg total?<br />the old prop is a little marked up, and i'm going to change it, it is a 14x14,..<br /><br />well trent i appreciate your concern for my safety, but i am not as dumb as i look/sound,..<br />we allways open the motor doghouse before we start the motor,. we always park the boat bow up with the bung out, so the bilges are really clean,.we trailer it to the water everytime.

 

[NOSLEEP]

Re: timing curve for omc 225hp

You are asking for trouble with the auto setup.<br />It only takes one mistake, and you can join the<br />long list of.. I thought it would be ok!

 

[lahnlubba]

Re: timing curve for omc 225hp

again thanks for reply NO SLEEP in regards for my safety,.. but if you have no usefull input regarding timing please keep the tired old rhetoric to yourself thanks. It is so annoying to have people reply posting opinions that are just obvious and have been said 100.s of times before,..and really do no good, and are unlikely to change the course of action being initiated any way happy boating!<br />nick

 

[NOSLEEP]

Re: timing curve for omc 225hp

Knock yourself out!<br />Happy boating.

 

[akriverrat]

Re: timing curve for omc 225hp

i was going to post pertinent federal and state regs but they aren't. canada. i won't be near you so i won't be hurt if it happens. my marine legal version hei starts advancing right off idle up to 3200rpm fully advanced. my buddy with zz4 had to dump hei because it couldn't produce enough spark at 4000-6500rpm. msd.

 

[lahnlubba]

Re: timing curve for omc 225hp

thanks mr river rat, the motor sits almost above deck in this boat,. the back of the dog house has an open space between it and the transom,..and we always lift up the cover before we launch , to check vital fluids etc,.. so i feel confident that a "kaboom" won't happen,.. The other boat a 26ft bayliner cierra sunbridge, its a different story with the motor below decks,....<br />thanks for the info on the timing curve,.. i'll be buying the spring and weight kit for the distributor.<br />Am also just in the process of putting the heads back on a 93 corvette lt1 motor, we are gonna run it with a carb, and an msd set up,<br />nick.

 

[akriverrat]

Re: timing curve for omc 225hp

UScg considers engine compartment with 15 square inches open to atmosphere per net cubic feet of engine room (l x w x h - space engine takes up) to be an open engine space and not need a bilge blower. hei vac advance should not be used. buds zz4 is in jet sled and wet exhaust. it was a bear stopping reversion from valve overlap. not sure if you meant lt1 was going in boat but that is something to keep in mind. engines car cams don't usually work well in boats-not enough torque.

 

[anesthes]

Re: timing curve for omc 225hp

<br />Automotive parts do not belong on a boat! <br />

I better remove that tree air freshner right away!<br /><br />Seriously though. I honestly do believe some components are modified to be safer in the marine environment, like fuelpumps, starters. Though I'd like to see the actual SAE or equal USCG requirements & drafts.<br /><br />On the distributor, I don't really see how the dist ITSELF is marine approved, I think the _CAP_ is whats different.<br /><br />

<br />My marine legal version hei starts advancing right off idle up to 3200rpm fully advanced.<br />

Thats good info to know the start and stop of the timing table, but what is "fully advanced" ? Fully advanced on my blown racecar is 24 degrees.<br /><br />

<br />engines car cams don't usually work well in boats-not enough torque. <br />

I'd like to see the full specs on a marine cam, to see what the power curve is suposed to look like in software.<br /><br />-- Joe

 

[lahnlubba]

Re: timing curve for omc 225hp

easy joe,... it's not a popular way here to question all that is marine!! <br />i was thinking if the motor doesn't have quite enough torque, i'd bump cam timing 4 ahead and see how that worked,..i was also thinking small block chevy should take 34-38 full advance, <br />i'm shooting for 6btdc @idle and starting at 12-1400 all in by 2500, what do you think?<br />nick..

 

[anesthes]

Re: timing curve for omc 225hp

It really depends on the C/R of the motor to begin with.. a 9.5:1 motor shouldn't detonate at 38 degrees, with good gas. especially in a boat where your running a max temp of 160 F.. <br /><br />-- Joe

 

[akriverrat]

Re: timing curve for omc 225hp

don't want to get in arguement. most marine engines are running under conditions most like an engine in a heavy heavy vehicle, going up a hill, 3/4 to full throttle. most like a truck or rv and the cams are usually quite similiar if not the same. IF you wet exhaust cam overlap is bad. especially at lower rpms. the engine will suck water out of the exhaust stream back into the cylinders. the closer the water is injected into the exhaust the worse it will be. full advance on my engine according to company that warrantied it is 32 at 3200. 92 octane.http://www.uscgboating.org/ if you want to see what is marine approved and why it can be found on this site or links provided on this site. no, it is not just the cap that is marine. primarily the legal concern on marine parts is not durability but preventing the "KABOOM". meaning, keeping gasoline contained, and if it does leak being sure electrical sparks will not ignite it. i care not one wit if you use non stainless headgaskets in a raw water cooled engine and they rust through and ruin the engine. same for waterpump, freeze plugs, and aluminum intake manifolds. nor are there any laws to that effect. nor does anyone care if you try to wet exhaust a high overlap cam and reversion ruins the engine. or if you can't get full rpm out of a motor that doesn't make it's torque and horsepower at a low enough rpm to do you any good. reality is, a boat is like a heavy truck racing up hill in a saltwater monsoon. i was just hoping to help a little and maybe save you some grief down the road. take it for what it is worth. or not.

 

[lahnlubba]

Re: timing curve for omc 225hp

preciate your concern mr rat, but you are assuming that i know little if nothing,.. and to ASSume will make an ASS out of U+ ME and i tried nicely to tell you that the motor does NOT!! have a long overlap cam,.. just a decent amount of lift, so reversion is NOT a problem at low rpm,.<br />happy boating.<br />oh, did you know that a balance tube between both exit pipes, willhelp to cure your 'reversion' problems? go ahead, ask why..

 

[galaxy]

Re: timing curve for omc 225hp

On the distributor, I don't really see how the dist ITSELF is marine approved, I think the _CAP_ is whats different.<br /><br />I believe marine distributor's have spark arrest vents on the bottom.

 

[akriverrat]

Re: timing curve for omc 225hp

why?

 

[lahnlubba]

Re: timing curve for omc 225hp

when you build a balance tube between the exhaust pipes of a v8, it makes the time between exhaust pulses shorter,therfore decreasing the 'sucking back or reversion' of the exhaust/intake overlap timing of the camshaft.<br />It gives 8 closer pulses shared equally rather than 4 longer pulse intervals. Will make the exhaust a nice even tone rather than the staccato<br />sound of a bank of 4 firing thru their seperate pipes. <br />nick

 

[akriverrat]

Re: timing curve for omc 225hp

makes sense. wonder why its not done?

 

[JasonB]

Re: timing curve for omc 225hp

Galaxy, you are correct on the difference in a marine distro.<br /><br />WFIW, when I rebuilt the 302 Ford in my boat, I used high quality/performance auto parts like pistons, rings, oil pump, etc. I even used High grade auto gaskets for stuff like oil pan, carb to manifold, etc. However, I did use marine head gaskets, intake gaskets, exh. manifold gaskets. etc. The cam is an "auto" cam with the grind I chose. The cam is a single with an RPM range of 1200-4200 (factory redline for my engine) and it pulls like nobody's business. All accessories are marine (alternator, distro, carb, etc). <br /><br />I argued a number of hours with my brother over the marine gaskets. He's a mechanic and argued that the better auto gaskets would be fine. Bottom line was it's my boat and I want piece of mind knowing we did certain things by the book. <br /><br />There are places you can skimp or deviate, but I don't want to be stuck on the water because I used cheaper gaskets to save a buck, or have to fight a fire/explosion because I plopped an auto carb under the cover. Not worth it, but that's just MHO.<br /><br />If it makes sparks, carries fuel, or touches water, use marine. Heck, I still have a marine distributor and it doesn't even make sparks anymore. Gotta love electronic conversions.