Q about 1968 55hp rude

So i finally had the motor running fine in the yard on muffs took it to the lake this morning to run things out and get a feel for it on water and it wouldn't stay running long enough to get it off of the trailer, i could mess with the choke enough to get it running for maybe 30sec and then it would just crap out. I swapped plugs as i had an extra set in the kit i put in the boat and even swapped the fuel line and primer bulb as they were about 13 years old and way passed hard. discovered a needle was stuck on the bottom carb and got it fixed but still no go i get fuel to all of the carbs as i can take the drain screws out and once the gas drains prime it again and more comes out choking or not choking didn't seem to matter except the 1 time i had it running for about 30sec but it came to the same result. And another q i have has something to do with the reed valves i believe while the motor was in the water air would be rushing out of the carbs and i could hear it hissing it had to have been the air rushing back into the exhaust and pushing the air through because it would only do it for maybe a min or 2 and then after trying to get it running it would do it again so could i have a stuck reed?

Re: Q about 1968 55hp rude

Before going to the water......

Check compression readings on all cylinders. What are they?

With s/plugs removed, check spark which on that model should jump a 1/4" gap with a strong blue lightning like flame... a real SNAP! Does it? Note that the gap is important.... checking spark by using the spark plugs is a waste of time.

Try Using Champion L77JC4 plugs, gapped at .030 . What plugs and gap are you presently using?

Best to remove the carbureors, clean and rebuild them so as to know that thy are in perfect condition..... then adjust as follows.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note 1: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

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Re: Q about 1968 55hp rude

Compression from top to bottom 126, 125, 126. Spark would prev jump a 3/8th gap, carbs were working and were sync'd i'm going to check the fule pump again and see if the screen is stopped up, as for the hissing question i think i answered it the 2 holes at the back of my motor which i thought were the pee holes are actually exhaust relief holes, and could be stopped up still, would anyone know of a way to test that, if there was too much back pressure on the motor wouldn't that have caused a similiar symptom to this?

Edit: Sparkplugs are NGK b7hs? it is the champion equivilent and i also had champion plugs that i tried but got the same issue, will recheck spark quality and get back to you, may be tomorrow at work until 11cst tonight

Re: Q about 1968 55hp rude

but if it started then it should have stayed running since it would have pushed the water out of the normal exhaust route...oh also goign to replace the needle and seats on them as i had done that with one that had stuck the neoprene had formed so i knew it would cause more issues in the future.

Re: Q about 1968 55hp rude

Impossible to have those exhaust relief holes plugged. The hissing is probably compression escaping past the piston rings at the cylinder exhaust ports.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

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Re: Q about 1968 55hp rude

well it's not impossible for them to be stopped up i had to run a wire up one and still don't know if i got everything out i still see dirt falling out some and i was messing with it for about 30 trying to get the right angle i even stuck wd40 up there with the straw and tried to get some loose.

Re: Q about 1968 55hp rude

Was that engine in a rodent infested shed for some time..... small field mice getting in via the thermostat water relief holes, something of that nature? I can't imagine that inner area becoming clogged any other way. Blow it out with compressed air.

(Exhaust Relief Ports - Exhaust Housing (Inner/Outer)
(J Reeves)

The long housing between the powerhead and the lower unit is called the exhaust housing. There is a inner housing within it that has a heavy duty seal around the bottom of it, or heavy duty seals around a inner extension between the housing and the lower unit.

The red hot exhaust travels down thru that inner tube and out the propeller with a somewhat supply of water to cool the propeller hub. A good amount of water surrounds and fills the space between the outer and inner tube, otherwise the outer housing would get so hot that the paint would burn off.

Some water pumps, for some reason (differing even when new) exert a great amount of water pressure, and if the exhaust housing seals are in perfect condition, the water fills the tube to a point of overflowing.

This brings into play those two holes or slots, whichever the engine might have, at the top rear portion of the exhaust housing just below the powerhead.

Now, if those two holes/slots weren't there, water would continue to flow up into the cylinders. Water not flowing out of those holes is no concern for alarm UNLESS that outer housing suddenly becomes extremely hot..... the warning horn should sound long before that happens.

The main reason for those holes being there (exhaust relief holes) is that when at an idle, there is an extreme amount of resistance encountered by the exhaust trying to escape due the fact that the outlet via the propeller is now blocked by a wall of water. The escape route in this case is for the exhaust to escape out those two holes, otherwise the engine would slow down quite quickly and die. If exhaust cannot escape, air/fuel cannot gain entrance to the engine.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

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Re: Q about 1968 55hp rude

As a matter of fact lol, it was there 13 years there is even a petrified mouse i found at the front i thinkg im going to glue a mason jar to the front and make him my first mate. ok, I'm going to start with those since on mufs it was a go but in water it was a no. I'll report my results sometime tomorrow, thanks joe