Calling all OMC experts, you can't make this stuff up....

[KaGee]

Re: Calling all OMC experts, you can't make this stuff up....

http://www.pertronix.com/ <br /><br />Follow the links.

 

[Striper Blues]

Re: Calling all OMC experts, you can't make this stuff up....

The saga continues. New distributor definately improved performance of timing advance however, she still deteriorates and dies after she gets hot. I have replaced entire fuel system (ran her on external tank, new fuel pump and carb. <br /><br />Can a vaccum leak cause her to bog and pop through carb during accel? After she is good and warm she won't run above 1000 rpm with out fading to a stall. I disconnedted the linkage to carb and pump, plenty of gas from accelerator pump. This is a very niche problem. I'm wondering if it could be a vaccum leak (now long block build, maybe intake manifold?) or perhaps a wire shorting after, what sagging? OK I'm groping but, read above..... not much left to check.....Yikes and good night Irene....

 

[Richard Petersen]

Re: Calling all OMC experts, you can't make this stuff up....

Get a cheap vacuum guage and put it in a place that has FULL vacuum at idle. Get a squirting oilcan. Squirt oil at the edges of the intake manifold all around at a struggle speed. Also at the carb base and the plastic insulator if it has one. oil will raise the vacuum and RPM. Retighten the manifold bolts when cold. AND the head bolts when cold.Do you use ANY rubber or flex fuel lines?

 

[Striper Blues]

Re: Calling all OMC experts, you can't make this stuff up....

Cyclops, thanks for the advice... I do have some rubber lines, one from the tank to the floscan sensor and one from the sensor to the fuel pump. All but the line from the tank are brand new transmission oil cooler line, heavy duty stuff so I wouldn't get kinks coming out of the sensor.

 

[Striper Blues]

Re: Calling all OMC experts, you can't make this stuff up....

Update....as it turns out the distributor was defective as it wasn't advancing properly. However the bigger issue was that the rebuilt carb was heating up (I guess) and starving the engine for fuel. This lead to the popping and stalling. I put the old one back on and wahla. Of course the old one gave me an old problem, the vaccum secondaries do not work. I am chasing the rebuilder to replace the one I bought. <br /><br />This brings me almost full circle (ugh) except it gets to plane much better with the distributor. However, I'm still only seeing 3900 WOT about 23 knots. I have the right prop per Grady/White and supposedly the original out drive. It makes no difference to WOT if I manually open the secondaries and pour more fuel in (I can see it going in), the RPM at WOT remains 3900. <br /><br />I have a stainless prop (same size 15x17) that I will try this weekend, but I already know it won't get me to 4400 to 4800, the factory spec for the 460 OMC King Cobra.<br /><br />Is it only likely to be gear ratio ? All operating parameters are right on the numbers dwell, timing, vaccum, compression, etc.....

 

[whywhyzed]

Re: Calling all OMC experts, you can't make this stuff up....

you can change ratios to make the engine turn faster that's great, but that won't increase your speed will it

 

[Striper Blues]

Re: Calling all OMC experts, you can't make this stuff up....

Well the stainless definately runs smoother,and added about 50 or so rpm, so I tried a 15.25X15 which gained me about 400 rpm. Now she is 4200 at WOT. <br /><br />Should I be concerned? given the spec is 4400-4800 according to the OMC Manual and Grady White? Does it make sense to go smaller, after all I'm gaining rpms, but like the man says no additional top end speed. Is it even healthy for the engine to just run at higher r's?

 

[KaGee]

Re: Calling all OMC experts, you can't make this stuff up....

IMHO, you are really where you need be prop wise. You could tweak some more I suppose, but what would really be gained?

 

[whywhyzed]

Re: Calling all OMC experts, you can't make this stuff up....

I think you might be hauling a half ton of water under the floor boards or something like that

 

[Striper Blues]

Re: Calling all OMC experts, you can't make this stuff up....

P.S. Late last season fuel starvation problem reappeared and we found a piece of screen stuffed about 12" up inside the steel fuel line which connects to anti-siphon valve. You guessed it the screen was nearly blocked off. Have never had a stallling/popping problem since. <br /><br />Why then you might ask wasn't this evident when I ran it with an external fuel tank. I can't explain that, because I did hook it directly to the fuel pump bypassing the entire tank/line system in boat. Just one B**** of an experience. On the bright side I have virtually a new engine. ahem.....

 

[KaGee]

Re: Calling all OMC experts, you can't make this stuff up....

Congrats... You'll be set when the weather breaks. Y'all supposed to get a blizzard this weekend aren't you?

 

[kenimpzoom]

Re: Calling all OMC experts, you can't make this stuff up....

Dadgum I hate problems like that, but it is good to hear you have it fixed.<br /><br />BTW, it is possible to have totally different springs on each weight in the distributor. Not common, but it can be done if the distributor was dialed in that way.<br /><br />Ken

 

[rodbolt]

Re: Calling all OMC experts, you can't make this stuff up....

would have been to easy to attach a vacum guage to the suction side of the fuel pump and look for fuel restrictions, that system should have less than 4" vacum at WOT, if there is more you have a restriction between the tank fuel level and the pump.<br /> I get them everyweek. 500 in parts have been changed and it still wont run so they bring it in.<br /> over the years I have developed various test procedures to confirm or eliminate the fuel,ign and mechanical systems.<br />but a compression test,fuel system vacum test, spark and spark advance test will eliminate 90% of the issues in less than an hour. the sticky secondary issue is common, engine vacum tries to pull the shutters open and a vacum bleed passage tries to close the shutters via the diaphram on the stbd aft side of the carb. make sure all the linkage and shaft bushings are clean lubricated and corrosin free. and occasionally someone leaves out the secondary diaphram spring or installs the incorrect one.<br /> sometimes its more helpful to think of it as intake manifold presure instead of intake vacum. at or near WOT vacum is about 0"Hg or about 14.7 PSI.it sometimes helps in understanding how and why a liquid moves from the fuel bowl to the intake manifold.