View Full Version : Elbow too short
11-26-2006, 10:52 PM
"Hi all you expert marine engine folks (how is that for high expectations?)
I recently purchased a 1993 GM 181ci/3.0L 4cyl I/O with a Yamaha stern drive in my Godfrey Hurricane Deck Boat. I also have water getting into my crankcase oil.
It was quite a bit of water - about 1qt. The prior owner did not seem to be aware of this problem.
I noticed that the stern drive of this boat rides very low in the water when not moving. Nearly the entire lower unit is submerged. Could it be that the water is backing up through the exhaust manifold elbow ?
I can not visually see any cracks/corrosion in the block, exhaust manifold or the engine head. I removed both today.
What do you guys think ? Where does the water usually get in ?
11-27-2006, 07:50 AM
..."It was quite a bit of water - about 1qt. The prior owner did not seem to be aware of this problem. "
You may have to raise the height of the risers to get them further above the water line. You may be able to get an extension pice that sandwiches in between the risers to make them higher--I've seen them sold for other marine engines (like 454s that are famous for water ingestion). A few inches more height would help a lot.
11-27-2006, 09:23 AM
"I'm not sure if Yamaha uses an exhaust flapper in the exhaust system, but I would pull the elbow and take a look. They don't last for ever and yours may be gone. While you have the elbow off, look for signs of water in the exhaust portion of the manifold. This may render some clues, maybe a leaky gasket or a bad elbow.
Being 13 years old, I would have to say that it has not been this way since new or it would never have lasted this long. Most likely something has deteriorated over the years to cause this condition.
Let us know what you find.
11-28-2006, 09:30 PM
"Hi Guys - please suggest a place where I can get a new elbow - or elbow extension. There is a LOT of room in the engine compartment above the engine. I wonder if one can get to carried away with too much elbow height ????
Jeff, have you no faith in your boat sellers? (Just kidding!) I like the near-new condition 20' Hurricane Deckboat so much that some engine work will not get me down.
Rick, the boat has always been in fresh water (which seems to be ice most of the time) so corrosion is not a huge problem (at least I think it isn't). It does have a flapper - and it seems to flap just fine. It is covered with soot, but it flaps freely. When it is closed I do not think it would create an airtight seal however.
Thanks for your help!"
11-29-2006, 08:02 AM
"I like Rick's "flapper gone" theory, and it should be replaced, but i'd add at least 6 inches in height since you have the headroom. THere's nothing like having gravity work for you!
Where to by spacers....Humm....Gotta do some web searches I guess.
Try our host board FIRST, then these guys:
11-29-2006, 09:51 PM
"Good news! My head is warped !
The machine shop said that the head was warped to 0.012". The shop said that that is plenty of warp to let water in. (I hope he is right.) Anyway, they milled off 0.015" to make the surface perfect.
Thanks for the web sites Jeff. Since I have everything apart, I would like to take some preventitive action and replace the flapper and increase the height of the riser.
By the way, I FINALLY found what I hope will be a good shop manual on Ebay last night. According to the seller it is titled "1989 Yamaha Marine Stern Drive L4 3.0 Engine Manual Z". While mine is a 1993 - it should give me good head torque, valve adjustment, etc. numbers.
Take Care everyone, Jim"
"OK, now you need to use a spacer gasket to keep the added compression from being a problem. Removing >.007" is where it starts to increase. Or, you can go with higher octane gas."
11-29-2006, 10:43 PM
Thanks for tip Jim N.
The machine shop guy said that I would not notice any difference because my 4 cyl 3.0l was not a high performance engine.
I would be concerned about adding materials between my head and block.
I think that I will start a new post and get some more opinions.
The problem with higher compression is that it can combust earlier and that's not good. Low octane fuels burn faster than high octane and need lower compression in the first place.
12-08-2006, 09:04 AM
""I would be concerned about adding materials between my head and block."
You just use a Thicker Headgasket...... They're available in Several Thicknesses......
For your question about the Height of your Riser,......
The Industry Standard is a Minimum of 13" from the level of the Water Outside the Hull, to the point that the Riser Dumps it's water Into the Exhaust.......}"
12-08-2006, 10:58 PM
"I am nowhere near 13" ! I will definitely add an extender. Aside from hitting the top of the engine cover, I wonder if there is a problem with going too tall on the elbow ?
By the way Bondo, where did you find the industry standard ?
12-09-2006, 08:46 AM
"That I can't tell you,.......
It came up several times in discussions about boats, mostly with Volvo drives that were having Serious Back-flow Issues.....
In other words,...I don't remember Where to send you to See the references......I think it was supplied, With References, by a Working Tech who hangs out at another forum I hang out at....
But I Do remember that 13"s IS the Key......
That's from the Water OUTside the Boat,....."
12-09-2006, 12:57 PM
"Here is where it comes from:http://www.marineengine.com/discus/messages/3/40113.jpgMerc Application guide"">
This is a page out of the Mercruiser inboard application guide. I can't tell you the rule is the same for I/Os.
12-09-2006, 02:48 PM
The higher the better. No problem.
12-10-2006, 10:26 AM
Thanks Rick and Jeff!
You are clearly better at finding this stuff than I am.
I was concerned that I might be overloading the water pump by making it push the water up six inches higher. I was also worried that the water that is pushed up six inches would be of sufficient volume so that when the engine was shut off it would get into the exhaust valves when it came back running down the engine side of the roller coaster.
12-12-2006, 06:40 AM
..."I was also worried that the water that is pushed up six inches would be of sufficient volume so that when the engine was shut off it would get into the exhaust valves when it came back running down the engine side of the roller coaster."
You are a worrywart (like me!) It'll flow right out the back like a syphon (which is what it's like). No sweat.
12-12-2006, 07:41 PM
That Water joins the Exhaust flow After the Hump,......
A Good 6"s past the Up part of the system.....
Unless you were to park that boat on it's Bow, Straight Down,......
Or have a Riser Rot Out,.....
That Water Can't climb back Up the Hill........"
12-12-2006, 08:26 PM
"I am busted! Worse yet, I am also a perfectionist!"
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