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What happens if cavitation plate is missing

junieb247

Member
"Hi guys, took our 86 Bayliner

"Hi guys, took our 86 Bayliner Capri out for the first time. It's AQ131A motor ran fine it seemed, but the RPMs...we never even took it over 3000 or so because it seemed the back of the boat was digging in. Sounded like the engine was dragging, but it ran fine, just no speed. We didn't want to overdo it and watched temp and other readings carefully. This was our first time out, remember, and so I'd like to ask a couple questions. The water, coming out behind the boat, was shaped like a large whale's tail laying on the water. The propeller is the original size recommended for Volvo penta LH 15x17. (We might have reached about 10 MPH at 2500 RPM or so, and didn't want to strain the motor because it sounded bogged down.) Tomorrow we are going to check the trim on the sterndrive and recheck all our fluids to see that all are still normal. If the Cavitation plate missing cannot cause this kind of effect, I think we might need to have it looked at professionally.

What do you think?

Also, we were in fresh water lake, running the blower. We never ran hot according to the guage, but should there always be water in the fresh water reservoir, even when operating in and using fresh water blower? We keep reading reference to it, but think that is for salt water operation; it's not clear in the manual.

Thanks for your input!!!"
 
"The back of the boat digging

"The back of the boat digging in may be an indication the drive is not going down all the way. Check the weight distribution. People in the back and or a lot of gear in the back. The cav plate is part of the drive. If you're thinking of a plastic dole fin. these are not required but. some folks use them to help an over propped boat or a heavy boat to get on plane better. You could also have some mechanical issues.

There are 2 tanks on this system, one for green juice and one to cool the green juice. The tank on the left as you look at the engine from the front will not remain full without engine running."
 
"The manual calls it "Cavi

"The manual calls it "Cavitaion plate with exhaust outlet" so was wondering if improper exhaust was the problem. We know very little about marine motors/sterndrive. Learning as we go, though!

We had one cooler with us, no other major gear; towels, etc. and total of about 545 pound of humans
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. We did not sit in the back two seats and the two adults stayed on opposite sides of the boat. SO, sounds like the drive is not keeping position? We did have one prob. when we first launched. The drive lifted up in reverse and got stuck. Hmmm...to find the parts responsible for keeping drive down and stable, where do we start looking? Thanks Boatrep!"
 
"If the exhaust is shooting st

"If the exhaust is shooting straight down onto the prop., couldn't that be interfering with the speed? If it were just a cavitation fin, then I wouldn't ask further, as I don't feel that would be a big issue.

Also going to look further into reverse pawl mechanism...see if it appears intact. If so, will try hole three on the trim adjustment unless you think otherwise.

Ordering SELOC repair manual today - too many high recommendations to ignore. Only had the boat a week but want it good to go! Any suggestions on a good place to find/order used parts? Thanks again...you guys are awesome in your knowledge and willingness to help others!"
 
"OK, looks like the drive is N

"OK, looks like the drive is NOT locking down...also like maybe the drive motor support (you lock in when tilted up) might not be in the right position when unlocked and interfering with the drive lowering completely into position. Where is there reference to this motor support part so we can check for correct part and position. Can't see it on any of the manuals so far, but searching. If we get this fixed, maybe we can reach 30 mph? IF ONLY!! Must also replace bellows first though, it looks like. OH BOY!!!
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LOL"
 
"the "drive motor support&

"the "drive motor support" if I'm understanding You correctly, should not be part of the drive. remove it to run the boat. also make sure tilt is fully down, as it will release reverse lock if not. missing exhaust snout should not affect performance."
 
"Hi Scott, thanks! Took off th

"Hi Scott, thanks! Took off that support and with the drive alway down in place, it's not "locking" into position, if it should be. However, that may not be why we can't get any speed; wouldn't the drive be held in the proper place by the propeller's force while running forward? Just wondering...

We have found a small tear in the bottom bellows and an oil leak in the bellows above that one. Would this cause the problem I described with the power? If not, we might have more than a bellows/sterndrive issue. ICK!!"
 
"OK, let's clarify somethi

"OK, let's clarify something here. What do you call the "cavitation plate"? Is it part 4 in this link?

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&grou p=1930&GroupList=1923,1922,1899,1901,1902,1903,1904,1900,1924,1905,1906,1907,190 8,1909,1910,1925,1926,1911,1927,1912,1913,1914,1915,1916,1917,1928,1929,1930,193 1,1932,1939,1919,1934,1935,1920,1936,1921,1937,1938,1940

If so, you definitely need to install one if you don't have it, otherwise the exhaust will go in the wrong direction and negatively affect the propeller thrust.

Now, regarding the "tear" in the bottom bellows. Is it a "pinhole" pointing downwards? If so, this is supposed to be there in order to drain any water that may be left in the exhaulst after you tilt the outdrive to put the boat in a trailer.

Regarding an oil leak in the upper bellows, <font color=""ff0000""><u>that's bad</u></font>. Because if there is an oil leak, there will be water ingress when the boat is in the water, and that will end ruining (if it has not done so by now) the universal joints. This could also be in indication that the input shaft seal is gone.

Now, when the drive is all the way down, you should not be able to pull it back by hand. It should only release when you either hit an object at high speed, or when you tilt the outdrive.

For what I see, your boat is not planing; it cannot do so at 2500 RPM and 10 knots. How long is your boat: 17, 19 feet? You may very well be overpropped, or have a bent blade in your propeller. Under normal conditions, you shold be able to plane around 3500 RPM (or higher) if you are using the right size propeller."
 
"Not metioned before, so I add

"Not metioned before, so I add it to the existing info.
Your drive LIFT motor (electrical motor with a long worg-gear)) is just that, only for lifting/tilting the outdrive. Not to be used for running. You adjust the trim angle by moving the rod on the drive shield.

Also, I'd pull the propeller and check what size (diameter and pitch) it has. Easy work, with boat in water or on land."
 
"Absolutely the part! The Vol

"Absolutely the part! The Volvo manual figure 7 points to it and calls it "cavitation plate with exhaust outlet". I guess I miss-named it. OK! Learning as we go...it's a 19ft Bayliner Capri Cuddy Cabin with Volvo AQ131A Penta 275.

The prop is what the boat calls for, a 15X17 LH rotation one, so we didn't want to change that until we felt any problems were repaired. Was afraid we might compensate for something bad, and end up tearing up the engine, as we are newbies to this whole game. Just got the boat and are working to get it good to go.

We only use the drive lift to lower and raise the stern drive, so no problem there. BUT the lower bellows has a small tear right where the band is. The upper one definitely has a slow oil leak-out and will have to be replaced. While doing this, I've read that it's best to go ahead and replace U-joints if needed, SO will check them AND the seal you mentioned. You refer to the seal washer on the spider, right?

Have ordered the spring that connects to the pin on the stop shaft (pawl area); have already followed instructions for adjustment, but can't see any other reason why the lower unit doesn't lock in place. All the parts seem to be OK; there is a little play, but doesn't seem excessive. Hope the spring will make the difference, although I have read that rarely do they wear out... Couldn't think of what else to try!

We'll order the exhaust outlet and bellows, and inspect the U-joint as described in the SELOC manual. Could the drive problems we've talked about BE the reason for not being able to get up any speed? We don't expect to pull skiers, but would like to go fast enough to plane out and pull a tube if we wanted to!

It would be great if this was the only problem we end up with this year... THANK YOU!!!!!!"
 
"IF you ran the boat with the

"IF you ran the boat with the lifting screw extended, then IT is holding the drive up (and is wrecked by now. The screw is not strong enough to withstand any throttle usage--it's merely to raise the LU up.) Now, if this is the case, it would explain both problems: Why the boat won't plane, and why the LU popping up in reverse (since the latch can't engage.

I'm assuming yours is about a 28 footer? On my old one, the LU had to be all the way in, with the rod at position one, for it to plane off and run worth a darn.

Jeff

PS: Forget 30 mph in that hull (if it's a mid-80s 26 to 28 footer). And even dropping in a 454 won't make it run over 29 mph, but it'll cruise all day at the mid-20s with a good small block. It's the way that hull was designed. Mine ran best by far with a 15 x 19 pitch prop. Wouldn't do a thing with a 15 x 17 or 18."
 
"Uh...lifting screw? Not foll

"Uh...lifting screw? Not following you on that term. I will see what I can find by that name when I have time to search. Have to go to work!

If you have time to specify what you mean, that'll help, too!! BBL..."
 
"after changing u-joint bellow

"after changing u-joint bellows (and u-joints if needed) set trim pin in bottom hole for testing. you can raise it later if needed. give it some gas to get on plane, then back off. make sure reverse lock moves freely, and locks. (can be checked on trailer. check spring in center of lock, and check pawls for wear.(doesn't take much) also make sure there is no side to side movement. (pin should hold it staight. check drive oil level.(top plug is dipstick) if you can't on plane, you may have an engine problem. havve you had a tune-up?"
 
tried to e-mail some pictures.

tried to e-mail some pictures. not sure if they went. maybe twice. electronicaly challenged.
 
"Sneaking in from work to tell

"Sneaking in from work to tell you YES, got them!! Three times...which is fine, as we are STERNDRIVE CHALLENGED. Will definitely use this info. How in the world could we run the boat with that lifting screw extended...we did put the drive all the way down before running, it just seems it doesn't lock in. I HOPE, anyway. Can't imagine that it would get stuck in an extended position without us knowing it, but it def. sounds like another item to check! Thanks a million for the pics."
 
"If you want to see what/how i

"If you want to see what/how it looks, go to:
http://www.dougrussell.com/partscatalog/volvo_omc/
then "Volvo Parts" and clikc your way to your engine/drive. Gives you a good bview of the lifting screw (electrical motor with worm -gear) as well as the latch and the release rod.
I think you'd be fine on the size prop, maybe go down to a 14x17, but the 15x17 will not give you any blazing acceraleration (which you are not looking for anyway)."
 
"Hi again...checked that lifti

"Hi again...checked that lifting screw and it looks just fine. Whew! Watched the drive go up, the pawl move as if it were disengaging; watched the drive come back all the way down and the pawl move as if it were about to latch, but it never locked in. I am thinking that replacing the spring might be just what it needs. Unfortunately, there is more work to do on the bellows. The exhaust one is not as big a concern as the one over the U-joint, though. That's the next item to check! Will let you guys know what we find; you've been a great help!

We'll be back very soon!!"
 
"Have a look at this link:

"Have a look at this link:

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&grou p=1916&GroupList=1923,1922,1899,1901,1902,1903,1904,1900,1924,1905,1906,1907,190 8,1909,1910,1925,1926,1911,1927,1912,1913,1914,1915,1916,1917,1928,1929,1930,193 1,1932,1939,1919,1934,1935,1920,1936,1921,1937,1938,1940

You may want to check that the thrust sleeve 47 is not jammed; that push rod 46 is not deformed; and that the thrust sleeve protrudes no more than 0.5 to 1.5 mm with the shift lever into forward (it should not be touching the tilt mechanism pressure plate when the outsrive is down!!!). The Seloc and Clymer manuals explain how to makethe adjustment."
 
"OK; but after watching this p

"OK; but after watching this part yesterday I think it's good. The sleeve is shiny and lubed, and only a bit of it shows when the drive is down. Maybe just the flat piece (pressure plate?) on the end of it, which is 3 to 4 inches away from the drive when the drive is down. It's all the way up...we'll check it and see if a picture of it in this position can be found just to be sure. May take one! Thanks a bunch!!"
 
"Two more thoughts,

With th


"Two more thoughts,

With the boat out of the water, remove the hose clamp from the drive bellows (drive side, not bellhousing side), then slide forward the bellows so that you can have a look at the U-joint assembly. If the area is full of oil, it is a sign that the seal I mentioned is gone and needs to be replaced. Also, if you find water (or milky oil) or the u-joints look rusty, consider not running the boat until you replace the u-joints. By the way, if you heard a growling sound or felt vibration in that area when you were running the boat, that would also be an indication that the u-joints are gone.

The second though was to make sure that you can move the retaining pawl mechanism freely by hand, as some parts could be seized because of lack of use. Make sure you spray all the stainless parts with WD-40 and that they move freely."
 
"OK, Pescador! Thought maybe

"OK, Pescador! Thought maybe the hose clamp wasn't tight enough on the housing side; we are going to thoroughly examine the bellows today. We are taking all advice given for checking things out! Learning a lot, too, thanks to all you guys here. Trying like heck to be able to take it out again by the 25th, so will let you know what happens!!"
 
"Here's where we are now:

"Here's where we are now:

Pawl is not siezed, we see it moving and can move it by hand.

Took off the bellows to see U-joint. Didn't take it all apart, but the U-joint itself looks almost new. There is no corrosion or excessive play from what we see at this point. There was no noise from it that we know of, either. HOWEVER, there is/was about a cup of oil in the bellows. The oil is a gold/tan color and is not transparent. Is the bellows supposed to be completely clear of oil? There is small tear under the band you instructed us to loosen to check it, and I think we can repair that. But if we have to remove all the parts to get to the seal, we might as well replace the bellows while we are at it. If the seal needs to be replaced, is that part # 19 on this page? http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&grou p=1921&GroupList=1923,1922,1899,1901,1902,1903,1904,1900,1924,1905,1906,1907,190 8,1909,1910,1925,1926,1911,1927,1912,1913,1914,1915,1916,1917,1928,1929,1930,193 1,1932,1939,1919,1934,1935,1920,1936,1921,1937,1938,1940
Now one more thing...can the pawl not latching down cause the boat not to get the speed to plane? It's Amature Hour!!
"
 
"Hey it looks like Dave G unde

"Hey it looks like Dave G under the "U-joint" heading has the same boat as we do! And he is talking about a leak, too. I have not yet looked at the oil in the case, but read where it says it should not take over 2 oz. Did I misunderstand that statement?? If not, am sure we have a leak, as we put in at least 6 oz to get the oil to show on the dipstick. Our dipstick doesn't have a line to mark the proper fill level, but I assume midpoint on the flat end. How would I get oil out of the case to see if it's the same milky tan as what we found in the bellows...or maybe it doesn't matter, just replace whatever seals?"
 
The approximate oil capacity o

The approximate oil capacity of the outdrive is 2.7 US quarts (2.5 litres). The oil is drained through the bottom of the outdrive (remove the screw). Consult section 11 (Maintenance) in your Seloc manual for this.
 
"I kid you not, I do know wher

"I kid you not, I do know where the oil goes and and how to drain it. I had it overfilled the first time I added some and had to let some out. That 2 oz statement came from the online instructions for something I was reading when I looked up the U-joints. Maybe it was some other gear oil reference that I didn't catch.

I wrote to SELOC and requested them replace my online manual with the printed one that all you guys have, too. Hopefully that will help! The online one doesn't list the parts I need to replace or what seals to check, and no troubleshooting for oil leaks, etc. Without input from all of you, I would be sunk!!"
 
"Well, we'll try to keep y

"Well, we'll try to keep you afloat for as long as we can.
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"You've all been GREAT. Ju

"You've all been GREAT. Just going to wait for the manual to arrive, I guess. The spring didn't fix the drive latching, The push rod looks like it's not going back up enough to let the pawl move up so it can latch. Can't tell for sure. It looks like the rod bows when we manually push up on the pawl. Plus, we still have to figure out what seals to purchase to stop the oil getting into the U-joint bellows. Our fun is just beginning, I think!! Maybe we'll have it ready by first snowfall.
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They have shipped our SELOC Ma

They have shipped our SELOC Manual!!! YAY!! Now maybe I can figure out what parts to order for that seal. I hope this book is specific about what parts do what function. We have to get this boat out on the lake at least!
 
I HAVE A 85 BAYLINER 305 GMC

I HAVE A 85 BAYLINER 305 GMC UNDER LOAD IT WILL NOT GO PAST 2000 RPMS ENGINE BOGS DOWN AND BACKFIRES OUT OF GEAR ENGINE WILL GO TO 3000 RPMS AND THAN BACKFIRE AND SHUT DOWN HELP!
 
"Have you run a compression te

"Have you run a compression test and checked the ignition timing? If not, I suggest you do so. If all OK, then your carb could be flooding."
 
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