Carb/Smoke/Fuel Quesition

[elbowcarey]

Hey guys,
I have a Mercruiser 5.7 350 magnum in a 88 Raven Countach, nice hull looks like a small cigarette (23').... Anyway I am having a lack of power problem for some reason and unsure what to check 1st.....
Used to be fine WOT at approx. 4600rpms and 60mph, now like 3800rpms and 40mph with white smoke coming out the exhaust. Also i noticed that gas was coming out the base of the carburetor.... Took it out, brought it home, and fired it up on the hose seemed to idle fine with no gas leaking out carb??? Took it back to the water and it ran the same way, lack of power and smokey??? What would be my 1st steps on this one to diagnose the problem? Thx Craig

[wagspe208]

First of all... you don't think outboard guys know anything about smoke except it is suppposed to, do you? LOL
1) Do a leakdown test, compression test is ok, too (leakdown is better, though)
2) Is there a vacuum plug blown off the carb? Float level ok? Gas coming out of the base is odd. Is the base gasket in tact? Carb snug (notice I did not say head bolt tight)
Sounds like a head gasket on the description. Leakdown or compression will tell you that.
Did problem start this year (beginning of season) or mid season? Exhaust could be cracked also if not propelry winterized.
Wags

[elbowcarey]

The problem started at the end of last season......

[wagspe208]

I'd start with compression and leakdown test then.
It is unlikely something is cracked since it started mid season last year. How are engine temps?
Wags

[elbowcarey]

engine temps are good, 170 ish, I did a compression test today 1 - 150, 2 - 170, 3 - 155, 4 - 155, 5 - 160, 6 - 155, 7 - 155, 8 - 150............ seems fine..... I did notice a few of the plugs were pretty loose, you think air leaking around a few plugs could be the culprit?

[elbowcarey]

Does the smoke only happen under load ? Reason being is I didn't find any issues, plugs were all the same new, lightly used and gapped properly, no water in the oil, oil looks good and level does not rise, compression ok, So I put it all back together and brought it up to operating temp 170-5 degrees and let it run for a while on the hose..... Nothing out of the ordinary, rev'd it up a few times in neutral - nothing, no smoke.. Turn it off and you get a little lingering smoke but I think thats normal for a hot exhaust and residuel water.... I am going to take it out on Friday and give it another run.....

[elbowcarey]

Ok got the heads off now...... one side came off pretty clean the other side looks like two of the rings on the gasket are peeling in two spots and there was water comng out of the lower head bolts..... I am gonna take the heads in to get them tested.... Do you guys think this is just the head gasket?

[thompy]

sounds like you have it under control, are the checking for cracks, and true mating surface, it sounds like the gasket to me though

[elbowcarey]

Heads checked out good, no cracks............ should have it back together this week..... does anyone know the torque settings for the rockers? I keep reading just to tighten until they do not spin then go another 1/2 turn?

[thompy]

its been awhile but i did that then adjusted while running backed them off till it started calcking and a 1/4 turn, its a little messy whith the oil pumping, i modded a valve cover,cut the top out and added some sheetmetal to make it taller to keep the oil in the motor

[elbowcarey]

Ok .... All back together and took it out today.......Not good,,,, still smokin' ???? This is what I noticed: low oil pressure (40), smoke at idle/wot, good power but slight hesitation, pissin me off........ white smoke.... could this be a bad oil pump? Could this be that the water flow is bad, slow water flow and hot risers/manifolds? Or that the exit ports on the themostat housing that go to the exhaust that have the check valves are too tight causing not enough water to flow? What next? I really need some good advice to get this fixed......

[thompy]

have you done a cyl leak down test

[elbowcarey]

Ok All back together, new risers/manifolds, runs/sounds great............but now I am noticing that the engine temp shows only like 100 but the risers/exhaust tubes/exhaust water are all way hot..... Shut it down and checked the tubing from the impellar back, no restrictions.... I am changing the impellar in the alpha one to see if that is the problem, not really sure what a bad one looks like....on the one I removed 3 of the fins are chipped up at the ends, seems like this would cause a pressue drop/air. Would you think this is the issue or could I have a bad sea water pump too? Also does anyone know the way this system works with the 6 hose configuation off of the thermostat housing, I ask because the two outlets (t) to the risers that have the two balls (check valve) is the reason I'm asking.... I don't think water is going through here to the risers because the thermostat I believe needs to open for this to happen and I think the risers/manifolds are too hot when the engine is only at 100 degrees.... Any good ideas????????????

[Hydrophobic guy]

Ok All back together, new risers/manifolds, runs/sounds great............but now I am noticing that the engine temp shows only like 100 but the risers/exhaust tubes/exhaust water are all way hot..... Shut it down and checked the tubing from the impellar back, no restrictions.... I am changing the impellar in the alpha one to see if that is the problem, not really sure what a bad one looks like....on the one I removed 3 of the fins are chipped up at the ends, seems like this would cause a pressue drop/air. Would you think this is the issue or could I have a bad sea water pump too? Also does anyone know the way this system works with the 6 hose configuation off of the thermostat housing, I ask because the two outlets (t) to the risers that have the two balls (check valve) is the reason I'm asking.... I don't think water is going through here to the risers because the thermostat I believe needs to open for this to happen and I think the risers/manifolds are too hot when the engine is only at 100 degrees.... Any good ideas????????????

Do yourself a favor and ditch that multi hose mess and circ pump and go to a two hose with a crossover. And if you don't have one now pick up a Holley DP carb.

[elbowcarey]

Impellar changed and now everything seems great................Finally.............Going out today for a test run let you know