expected hull speeds with yse8 yanmar?

[jawzzy]

I've had my 1975 24' Corsair restored and the motor overhauled these past 2 seasons, but I find my Bristol to be a real tank when it meets any kind of head resistance, whether water or wind. As soon as I get any kind of head wind, it drops to about 3 to 3.5 knots, and any kind of sizeable waves, and I'm down to 2 knots or below.

Now I've only owned this beauty for 3 years now, so I can't say what it used to be like, only what I experience. And that's why I'd like to get some feedback on others here who own a 24 inboard to compare with. I haven't replaced the exhaust manifold yet, and have been told it may be plugged, which could account for power loss. I also get a great amount of black smoke when under any high RPM's.

Thanks in advance for any help or advice.

 

[okawbow]

Sounds like you have a problem with something in the engine/prop. I have a 1976 corsair with the original YSE8. The other day, I powered into 20+ head winds, and heavy chop. I was doing close to hull speed.

If you are getting black smoke when you power up, you are overloading the motor. It could be caused by restricted exhaust, resticted air intake, improper valve lash setting, poor quality fuel, low fuel pressure, clogged injectors, improper injector timing, poor compression, fouled bottom, fouled prop, or wrong size or pitch prop.

Do you have a manual? There is a trouble shooting section that may help. You can see one at http://www.sailingboatefaki.gr/Engine Manuals.htm

What prop are you using? Mine is a 12LH7. Could yours be fouled? That makes a huge difference. I'd look at the valve setting first, and then take the exhaust elbow off, and clean it out. Check your head bolts for proper tightness, and go down the list. You shouldn't be getting black smoke, except for a spurt when you crank up the rpm's. Good luck.

 

[jawzzy]

Thanks for the confirmation and help with this, and by hull speed, you mean around 6 Knots I understand for a Bristol 24??

I planned to check the exhaust elbow first. The head gasket was just done, along with a rebuilt injector and injector pump. I also installed a new electric fuel pump, which leads me to my first question: I've just realized that with my Racor fuel filter, I've been using 2 micron filters, which are said to be like sucking thru a straw, but would that also be true with such a small engine and using a 12volt fuel pump? I just found out that I can get 10 microns if need be.

Found my prop id: 13LH12, and just what do you mean by "fouled" with a prop? that's a new one for me. I did hit it on the trailer last year, but it didn't seem to be too damaged. I tried to remove it, but couldn't get the Rudder off to do so...looking at getting this all done this fall professionally. Judging by the difference in our prop #'s, I may want to look at getting a new one, or repitch mine.

I'm going to ask the mechanic who did the injector install if he actually timed it, or just reinstalled it as it was, as well as the valve lash setting. My air intake seems ok, but I'm going to double check that too.

Another suggestion I was given was that perhaps my transmission was slipping, but again I'd have to leave that one to the professionals.

One more thing: the exhaust elbow gets SO HOT, it actually starts to burn the wood cover, and even burned my bed material my last 2 hour run, again perhaps a sign it's plugged.

I'll start looking into these things now that I have the boat back in the driveway for the season.

Thanks again for this and any future help It really helps to compare with someone who has the same setup!!!

 

[okawbow]

My Bristol 24 will do about 5.5 knots at 3/4 throttle. It takes a lot of wind and current to slow it down below 5 knots. A couple years ago, when the motor needed a new head gasket, and injector, the boat could almost be brought to a stand still in high winds and chop.

Your prop sounds like it might be too big, and too pitched, and is not letting the motor get up to speed under load. Maybe you should ask a Marine engineer. Also, does the shaft turn easily by hand? Is there any unusual vibration. By fouling; I mead barnacles or growth. If you don't leave the boat in the water, it's not an issue.

Are you sure you are getting cooling water through your engine? I can place my hand on the exhaust mixing elbow after the engine has run for hours, and it is only warm. I'd check the water pump and impeller.

It's easy to check the valve lash and injector timing yourself. The instructions are in the manual.

 

[jawzzy]

As stated earlier, I can only get 4.3 Knotts max, and that's at maximum throttle, and ONLY on glass type water. I've only had the boat 3 years now, but it's never gone faster than that till now, although it does seem to have gotten somewhat worse in adverse conditions. I'm going to look into the prop size for sure, as I need to get it fixed anyway. The shaft seems to turn easily enough by hand, and I do get vibration, but I believe it's the rudder doing it at only certain RPM's as it needs new bushings. The prop is NOT fouled.

I checked out the water pump last year, and all seemed good...the water coming out of the exhaust is not overly hot either, but after a few hours of running, I can't even touch the wood above the elbow without burning my finger, never mind the exhaust elbow itself I think I'm going to find it really clogged when I do get it off.

And thanks for the tip, I'll look into the valve lash and injector timing in the manual.

 

[jawzzy]

As mentioned earlier, I couldn't get the rudder off.....well I'm back at it again, but see no obvious way, and google searching has failed me. Does anyone know how to remove the rudder on a B-24?

 

[okawbow]

rudder removal

I'm also interested in the answer to this question. I've never had my rudder off, but it seems like it should come off by removing the packing nuts, tiller clamp, and lifting the rudder up off the pintle, and sliding the rudder and shaft down and out. Of course, you need to have the boat high enough that the rudder can drop.

Are you sure you can't pull the prop and shaft out by turning the rudder all the way to one side?

 

[jawzzy]

rudder removal

there's no room to get a wheel puller in to get the prop off, and even then, I don't think there's enough space to get the prop out anyway, and definitely not the shaft.

I'm curious, what are these packing nuts you refer too....all I see is the tiller clamp to remove, then I thought the rudder would do as you think...moving it up,out, and down....being on a trailer, I have the room to do so it appears.

 

[okawbow]

There's a packing gland and hose you can get to by crawling through the starboard pilot berth. I hope you're not claustrophobic. Probably just need to loosen, and make sure there are no dings or rough spots on the shaft above.If that doesn't work; the pintle on the Corsair, is bronze, and glassed into the back of the keel. I've heard of people with Cape Dorys having to grind out the fiberglass to remove the pintle, and then re-glass it to install.

My boat is in the water now, but I'm pretty sure I can swing the rudder over far enough to get the prop off with a 2 jaw puller.

You might want to post the question on the Ask all sailors forum. Surely someone has taken the rudder off on a Bristol or Pearson that has the same set-up.

By the way, I"ll pass on a tip, if you have play in the rudder where the pin sets in the pintle. Three years ago, I cleaned and sanded the socket out as best as I could, while not cleaning the pin. I then mixed some metal filled epoxy I bought at an auto parts store, and worked it into the socket around the pin. I wedged and clamped the rudder, so the pin was centered. When the epoxy had set, but before it was completely hardened, I turned the rudder. The pin had a new bushing cast in place, and zero play. There is still no play after 3 years and over 2 thousand miles.

Here is a picture of the prop aperature. Is yours like this?

 

[jawzzy]

Mine is nothing like that....here is a picture of mine....It also appears yours is prop is only a 2 blade, and mine a 3, so that me be why such a difference in sizes (13lh12 vs 12lh7). Here is a picture of mine....

 

[okawbow]

A three blade that big?!!! No wonder your motor can't keep up! It would take 30hp to turn that prop at full rpm's. I'll bet you can actually back your boat up under control though. Mine won't back worth a darn. I'll bet you would gain 1/2 knot in sailing speed if you switched to a two blade the size of mine. I set my prop vertically when I sail. Apparently, that helps my speed a lot. I won a club PHRF race Sunday, and have won and placed in many other hare and hound type races with my Corsair.

You need to have someone look at your set-up to see if that is the correct prop. It could be that your transmission is different than mine.

 

[jawzzy]

actually, I do back up "really" well, but I thought it was me

I've been trying to find someone who knows there stuff around here, but no luck yet, and that's why I've been searching the web for some answers....is there a plate or something I can find to identify my transmission for comparison? And I'm curious, just how do you know your prop is set vertically when sailing

Congrats on your wins too.....I can't even imagine my Bristol in a race...in 2 seasons sailing the North Channel here, I've only managed to pass 2 boats, and that was at the same time traveling together

 

[okawbow]

I think the manual or parts list should have a picture or decription that identifies the transmission. I seem to remember that there are two types. Maybe one has more gear reduction.

Your prop is almost certainly too large and too pitched for your boat. I've seen 35 footers with smaller props.

I painted a mark on my prop shaft to position the blades vertically. I put the shift lever in reverse to lock it. Don't hesitate to use big sails on the corsair. I can use my full main and a 155 genoa in small whitecap conditions. My boat likes to sail at about 25 degrees heel. If it gets too far over, I'll reef the main, but still leave the big genoa on until the water starts getting foamy. Corsairs aren't fast, but we can handle conditions better than most 24 footers. Last year, I averaged almost 5.5 kts on a 140 mile passage in the Gulf of Mexico. That's a good speed for any small boat.

 

[jawzzy]

thanks for the sail tips! I like the way it speeds up too with about a 25 degrees heel, but the wife can't take much more than 15-20 I actually put my 150 genoa in the water this year doing 5.8 knots, but that was a bit scary being the first time...was sure nice to know though that was probably it's limit

I'll check out the tranny id, and still looking into the prop change for SURE!!!!

 

[jawzzy]

Well, I've been busy this week.....I finally gave in and took the boat to a Marine shop (insurance claim) to get the prop, shaft and rudder done. At first glance the Pro thought for sure I was over propped too, but after confirming my engine and tranny setup, it appears I have a 3.1 ratio, and a 13LH12 is actually a bit under propped for my set up....specs call for a 15LH10, but apparently by dropping 2" in diameter, and increasing 2 for pitch equals "almost" the same performance. I knew the prop was slightly damaged, but the shaft DID turn out to be bent too, so new shaft coming as well as prop repair...they did remove the rudder to accomplish all this, and I've been told it was rather easy, and that they WILL show me how to do it myself when I pick the boat up...I will pass on the info when I've got it

These are the specs listed right on my YSE8(G) motor:
...................HP...... 7..... 6.... 5
Speed Crank (RPM) 3200 2600 2200
...........Prop (RPM) 1093 888 751

now as for the HOT exhaust problem (these guys have bee the MOST helpful marine mechanics I've ever got to provide such FREE advice and knowledge, although the $500 deductible I'm forking out might have something to do with that too ), it appears a previous owner fixed and welded the whole silencer and U piece together, but in doing so, DID NOT re-wrap it in fiberglass wrapping, as mine is a "dry" exhaust, with the water entering on the down side of the U shape, which leaves it to get VERY hot by design. $7 for fiberglass wrap, mechanic's wire and 5 minutes, and problem fixed ....and it was clear and NOT plugged as I thought I was going to find inside.


which brings me back to my original problem: black smoke and no power....now that I know the the exhaust isn't plugged, and the prop is the right size, there goes those reasons for black smoke...and with a rebuilt injector pump and injector done, guess that leaves only a few other things to check......like improper valve lash setting (will check), poor quality fuel (emptied tank, and will clean in Spring), low fuel pressure (electric fuel pump already installed), improper injector timing (will check), poor compression (new head gasket done last winter) or a fouled bottom ( hull bottom painted, but the "guys" said it looked good, and wouldn't be loosing much more than a 1/4 knot at best).

They didn't think my damaged prop and shaft were enough to contribute to either the black smoke or loss of power, but they are "pretty" sure the black smoke IS Fuel related, and not the motor itself, so that should help narrow it down in the Spring (already winterized it).

 

[okawbow]

Are they putting in a new cutlass bearing when they replace the shaft? Now is a good time to do that if there is any chance the old one is worn. The prop size makes more sense with a 3-1 gear reduction. I believe mine is a 2-1. I think a bent shaft is still possibly causing an overload. Once that is fixed, you will know for sure. I would still set the valve lash. All you need is a feeler guage and a couple wrenches. While you have the valve cover off; re-torque the head bolts, and check the rocker arm assembly for tightness. I had the rocker arm come loose on mine at a very inoportune time and the pushrods came out, causing the engine to quit. I almost got run down by a barge in the process. You also might want to inspect your high presssure pump for wear or dirt. Low pressure could cause the smoke. Also check your air intake to be sure it is completely open. I carry extra gaskets for the intake, exhaust, and head. The air intake tube comes off easily for inspection.

The nice thing about these engines, is the simplicity. When my engine quit because of the rocker assembly coming loose; I had it running again in 15 minutes. there's just not that much on these little 1 cylinders. If you have compression, clean fuel at the right pressure, and time, and enough air, it should run.

 

[leeschaumberg]

Hello Jawzzy
A couple things that you need to know -
Your hull speed -
Your engine horsepower at what rpm?
The propshaft gear ratio?
What does the engine rpm run in calm condition?
The engine will show black smoke when highly over loaded. Just a slightly bent prop or shaft will cause this. The boat's bottom and prop has to be as clean and smooth as a baby's bottom. The previous owner maybe just sold it instead of fingering it out! Take a compression test and rpm of the engine to ask with to get good info. Never - Never assume anything.

 

[jawzzy]

thanks for the info, especially on the prop and shaft.. once I get the new tach installed in the spring, I'll be able to start all these tests

 

[jawzzy]

well the Tiny Tach works GREAT, and an easy install really So with a clean Fuel tank, 2 filters, new shaft and prop, I was actually managed to reach 5.4 MPH, which I haven't done since I first got it, so maybe the damage affected my speeds more than I thought...the waters were calm though, and I still have problems getting tip hull speed in waves. The big question though is how much is towing my 8'/4hp dinghy slowing me down? When I hit 5.4mph this weekend, I left the dinghy at the dock for the first time, so maybe it's affecting my hull speeds alot more than thought (most said it would loose a 1/2 knot or so)as well as the amount of black exhaust I wasn't getting without it in tow. Any experiences with this one to pass on out there? As for fixing the mixing elbow, still VERY hot, even with the special tape applied...mine seems to have been rebuilt, and I'm not sure the water inlet being on the DOWN side is right....I've seen some pictures of newer mixing elbows, and they seem to have the inlet in the middle/top, if not even more to the upside of the elbow. Again, any thoughts here? THANKS for reading and your time