Prop Cavitation on Cape Dory 36 and and oil leaks on Perkins

[SAMiller]

We are in the process of purchasing a CD36 with a Perkins 4-108. We love the boat, it's a beauty. The previous owners have taken good care of it and we are very pleased with it. Two points of concern:
The engine seems to run fine below 2200 RPM but when taken above that, there is a loud noise and vibration from the aft lower part of the boat. We have been told this is due to prop cavitation. What can be done to eliminate this problem? Would a prop change help? Have others encountered this problem before? How did you solve it?
Also, there seems to be quite a few oil leaks on the Perkins 4-108. Since we've been in the automobile repair business, rebuilding engines has been a specialty for 35 years. We don't like the idea of an engine that leaks oil, but some have said this is normal for the Perkins 4-108... suggestions, comments and advice will be greatly appreciated. Thanks in advance for your help. Best regards, SAM



ShooseyQ@aol.com

[Bill Cahill]

I've owned my 36 for 3 months and also wondered/worried about this noise, on sea trial at was explained as prop cavitation, which does kick in at 2200+ RPM's, after lots of sails I've found that RPM over 2200 approaches hull speed for the boat (GPS clocked) and causes the stern to dig in with a large wake developing, I've also noticed a increase in engine temp on the 4-108 (to 195) when running over 2000, so... I've taken the cavitation as natures way of telling me I may have too much throttle on the boat. I ignore it in conditions where lots of power is needed, it sounds bad, but does no harm. I'll also check back to sea what the true CD36 salts say.

Bill Cahill
Galavant
New Orleans

We are in the process of purchasing a CD36 with a Perkins 4-108. We love the boat, it's a beauty. The previous owners have taken good care of it and we are very pleased with it. Two points of concern:
The engine seems to run fine below 2200 RPM but when taken above that, there is a loud noise and vibration from the aft lower part of the boat. We have been told this is due to prop cavitation. What can be done to eliminate this problem? Would a prop change help? Have others encountered this problem before? How did you solve it?
Also, there seems to be quite a few oil leaks on the Perkins 4-108. Since we've been in the automobile repair business, rebuilding engines has been a specialty for 35 years. We don't like the idea of an engine that leaks oil, but some have said this is normal for the Perkins 4-108... suggestions, comments and advice will be greatly appreciated. Thanks in advance for your help. Best regards, SAM

bcahill@loyno.edu

[Bill Cochrane]

The symptoms you describe (overheating, approaching hull speed, stern digging in, around 2200 rpm) indicate too much prop pitch. The CD36 was spec'd by the factory with a 15x14 fixed 3-blade. When I bought PHOENIX she had a maxprop, 3 blade, also set at 15x14 (ok, 13.8). I took 2" out of the prop last winter and am going to take another inch out this year. The 4108 has confusing specs: 4000 absolute red-line, 3600, and 3000 depending on usage. I'd like to hit hull speed (7.0) about the time the engine hits 3000-3200; right now I get to about 6.6 knots at 26-2700 and the engine is laboring...black smoke, tendency to overheat. (I also probably have a dirty prop and bottom, so can't really get to hull speed.) Looks to me like 15x11 for a 3-blade is a lot closer to reality. For what it's worth, I don't think cavitation is involved.

Bill
CD 36 #114
PHOENIX

I've owned my 36 for 3 months and also wondered/worried about this noise, on sea trial at was explained as prop cavitation, which does kick in at 2200+ RPM's, after lots of sails I've found that RPM over 2200 approaches hull speed for the boat (GPS clocked) and causes the stern to dig in with a large wake developing, I've also noticed a increase in engine temp on the 4-108 (to 195) when running over 2000, so... I've taken the cavitation as natures way of telling me I may have too much throttle on the boat. I ignore it in conditions where lots of power is needed, it sounds bad, but does no harm. I'll also check back to sea what the true CD36 salts say.

Bill Cahill
Galavant
New Orleans

We are in the process of purchasing a CD36 with a Perkins 4-108. We love the boat, it's a beauty. The previous owners have taken good care of it and we are very pleased with it. Two points of concern:
The engine seems to run fine below 2200 RPM but when taken above that, there is a loud noise and vibration from the aft lower part of the boat. We have been told this is due to prop cavitation. What can be done to eliminate this problem? Would a prop change help? Have others encountered this problem before? How did you solve it?
Also, there seems to be quite a few oil leaks on the Perkins 4-108. Since we've been in the automobile repair business, rebuilding engines has been a specialty for 35 years. We don't like the idea of an engine that leaks oil, but some have said this is normal for the Perkins 4-108... suggestions, comments and advice will be greatly appreciated. Thanks in advance for your help. Best regards, SAM

cochrane@clark.net

[David Sabourin]

We are in the process of purchasing a CD36 with a Perkins 4-108. We love the boat, it's a beauty. The previous owners have taken good care of it and we are very pleased with it. Two points of concern:
The engine seems to run fine below 2200 RPM but when taken above that, there is a loud noise and vibration from the aft lower part of the boat. We have been told this is due to prop cavitation. What can be done to eliminate this problem? Would a prop change help? Have others encountered this problem before? How did you solve it?
Also, there seems to be quite a few oil leaks on the Perkins 4-108. Since we've been in the automobile repair business, rebuilding engines has been a specialty for 35 years. We don't like the idea of an engine that leaks oil, but some have said this is normal for the Perkins 4-108... suggestions, comments and advice will be greatly appreciated. Thanks in advance for your help. Best regards, SAM

I have CD36 Hull#151 built in 1988. It has the Perkins 4-108 and has leaked oil from all kinds of places since it was new. Just about everyone I talk to that has this engine has had similar leaks. As far as 2200RPMs, I get hull speed (close to 7 knots) at about 2000RPM. The prop is original equipment and been rebalanced by Black Dog Props over in Kent Island about two years ago. The engine has just under 2000 hrs on it and has always performed well. Only occasionaly have I brought it up to 2200RPMs and that was in an emergency situation or a grounding trying to motor off. I've owned the boat since it was new and have traveled from Canada to Florida and estimate a total accumulated log of 30,000 miles. Hope this experince helps you and good luck with your 36.

David Sabourin
Madhatter 11
CD36 Hull#151



hatter11@erols.com

[Ken Coit]

Sam,

Make sure the engine mount nuts are tight - top and bottom. We tightened one very loose bottom nut and eliminated a lot of vibration and packing gland leaking.

Ken Coit
S/V Parfait
CD-36

We are in the process of purchasing a CD36 with a Perkins 4-108. We love the boat, it's a beauty. The previous owners have taken good care of it and we are very pleased with it. Two points of concern:
The engine seems to run fine below 2200 RPM but when taken above that, there is a loud noise and vibration from the aft lower part of the boat. We have been told this is due to prop cavitation. What can be done to eliminate this problem? Would a prop change help? Have others encountered this problem before? How did you solve it?
Also, there seems to be quite a few oil leaks on the Perkins 4-108. Since we've been in the automobile repair business, rebuilding engines has been a specialty for 35 years. We don't like the idea of an engine that leaks oil, but some have said this is normal for the Perkins 4-108... suggestions, comments and advice will be greatly appreciated. Thanks in advance for your help. Best regards, SAM

ken-shelley.coit@worldnet.att.net

[Ryan Turner]

your engine alignment and the cutlass bearing. I've been told that a worn cutlass bearing can cause all the vibration at the stern. I don't think that prop cavitation is the problem.

Ryan Turner
s/v Zenobia
CD33 hull no. 100
Oriental, NC



rdtec@aol.com

[Matt Cawthorne]

Sam,?br? ?br?Vibration ..... I suspect that your problem is not cavitation. I had Kastell Prop shop in St Michaels Md re-pitch the original 15RH14 down to 15RH12. The original props were made by Essex machine which is somewhere in New England. It was a relatively low DAR (disk area ratio) prop. The low DAR gives lower drag under sail, but is more likely to cavitate. While messing around with the pitch I did some speed trials. After checking the tachometer calibration I took some speed versus RPM data and looked at some Bp-delta curves to try and choose a new pitch. The thing is that I pushed the engine all the way up to something like 3200 rpm with the 15RH14 prop and to 3600 RPM with the 15RH12. Both noise and vibration went up with RPM, but there were no sudden jumps. There was no large jump in vibration. I think that you should get a surveyor or diesel specialist to check the boat out. I would start by cleaning the prop and checking the cutlass bearing and engine alignment. I would also look into engine mounts. It may have something to do with the injection system if the vibration is due to uneven engine operation. ?p?Leaks..... I heard of a legend that there was once a Perkins 4.108 that didn't leak oil. When I bought my boat I hired a Perkins specialist to stop as many leaks as possible. He did a good job and it is down to leaking a teaspoon or two each hour. I am tired of that leak after 6 years and plan to take a trip back to see him and see if he can get that last one. ?p?The CD-36 is a great boat. I never intend to 'upgrade'. The boat is initally tender, but if you learn to reef the main early you will find it an absolute joy to sail on both the bays and on the open ocean. ?p?Good luck,?br?matt?p??p??p?: We are in the process of purchasing a CD36 with a Perkins 4-108. We love the boat, it's a beauty. The previous owners have taken good care of it and we are very pleased with it. Two points of concern:?br?: The engine seems to run fine below 2200 RPM but when taken above that, there is a loud noise and vibration from the aft lower part of the boat. We have been told this is due to prop cavitation. What can be done to eliminate this problem? Would a prop change help? Have others encountered this problem before? How did you solve it??br?: Also, there seems to be quite a few oil leaks on the Perkins 4-108. Since we've been in the automobile repair business, rebuilding engines has been a specialty for 35 years. We don't like the idea of an engine that leaks oil, but some have said this is normal for the Perkins 4-108... suggestions, comments and advice will be greatly appreciated. Thanks in advance for your help. Best regards, SAM?p?



mcawthor@bellatlantic.net

[SAMiller]

Thanks so much for everyone's help with this problem. We will explore all the avenues you've suggested and replace or repair where necessary. As soon as we solve the problem, you'll be the first to know, via this list... and what it took to solve it. We're determined. We do agree that the boat is worth a little effort. Everything else about the CD36 we love... Happy sailing, SAM

We are in the process of purchasing a CD36 with a Perkins 4-108. We love the boat, it's a beauty. The previous owners have taken good care of it and we are very pleased with it. Two points of concern:
The engine seems to run fine below 2200 RPM but when taken above that, there is a loud noise and vibration from the aft lower part of the boat. We have been told this is due to prop cavitation. What can be done to eliminate this problem? Would a prop change help? Have others encountered this problem before? How did you solve it?
Also, there seems to be quite a few oil leaks on the Perkins 4-108. Since we've been in the automobile repair business, rebuilding engines has been a specialty for 35 years. We don't like the idea of an engine that leaks oil, but some have said this is normal for the Perkins 4-108... suggestions, comments and advice will be greatly appreciated. Thanks in advance for your help. Best regards, SAM

ShooseyQ@aol.com