m18 universal engine

[newboatowner]

Merry Christmas to all of you.

I have an on going problem with the engine in my 1980 Catalina 30 that drives me to distraction. I love the boat and I know the boat. The only disappointment is the engine - an M18 Universal. I have been on this forum many times trying to figure out if it is running right or just down right undersized. The consensus is that it is just too small for the size boat.
I am still, however, trying to boost the power a bit because I feel that there is some mechanical problem that is making this small engine smaller.

I have rebuilt the injector pump (blowing smoke and that did the trick). I put in a new fuel pump, changed filters, cleaned out the tank and speak to it gently every time it starts but I find that the maximum RPM that I get under load is 2,300.

When the boat was pulled, I took off the two blade prop and found that it was a 12 incher. I do not know what the pitch is but I will be bringing it to a shop for measurement in January. The specs call for a 13x10 for maximum performance.

The question is: Is this undersized prop a potential cause of the low RPM? I would hate to invest in buying a 13x10 for no reason.

 

[Calif. Ted]

Have you checked the exhaust elbow recently ? When clogged it's like a banana in your exhaust pipe only it comes on slowly.

 

[Capt jgw]

The M18 is only 14 hp, so it is undersized for a beamy 30 footer. The earlier C30's came with the M15 which is only 11hp and really undersized. The engine is probably running s well as it can, but do check an clean the exhaust system, especially the mixing elbow. Of all's good there, you're probably over propped. Sounds like you've covered everything else. Do you know if the boats ever been able to make more rpm's? If not, then it's the prop. Your prop shop can probably flatten the pitch by a couple inches, that will help a lot. The pitch has a lot more to do with engine load than diameter.

 

[Maine Sail]

#1 Confirm tach readings with a digital photo tach. You can't go any further until you know what the engine is actually turning for RPM. What I find in about 8 out of 10 times in these situations it is an incorrect tach reading coupled with an over prop situation. The other times are simple things like the fuel rack throw needs to be adjusted.

#2 Make sure throttle arm is fully advancing to WOT. Test engine RPM in neutral with no load and also neutral at WOT under load.

#3 If engine is getting to accurate max rated RPM at WOT in neutral, but not under load, the likely culprit is an over prop situation. You can still have a 12" prop that is over pitched for the boat...

We owned a C-30 and re-powered with an M-20 which is not much biger than the M-18. We had way more power than we needed but she was propped correctly. A little under propping is usually better than a little over propping, with small engines so best to err on the side of under propped to account for a high alternator load....

 

[weinie]

M18 also.
http://forums.sbo.sailboatowners.com/showthread.php?t=142183

Jump to the end for the solution.

 

[newboatowner]

Thanks so much for your comments.
How can I check the exhaust elbow? Do I have to disassemble?
Forgive me but what does WOT mean?

 

[Stu Jackson]

Usually Universals don't have "exhaust elbows". they have "exhaust risers" which are pipe with a smaller pipe nipple welded into the side of the main exhaust gas pipe between the engine manifold and the muffler. It is usually Yanmars that have exhaust elbows, a one piece gizmo combining the raw water input to the exhuast gas pipe close to the engine, and thence to the muffler.

To check a Unive4rsal riser, find the place where the water from the HX goes into the exhaust gas pipe from the engine to the muffler, usually pretty close to the muffler.

It's also shown in your boat manual. Get one somewhere online if you don't have one.

WOT = wide open throttle

 

[Bob4203]

My 1988 Mark II is powered by the M-18 and do not despair too much! I do not think your engine is slower, its simply SLOWER! I sail in an Army Corp impoundment (Lake Lanier, GA) where the only resistance I might encounter is the wake from a bass boat or houseboat and yet at high rpm's (2K +) I am not making way that quickly. I have been along side other Catalina 30' powered by the M-25 with 22 horsepower and its like a three legged dog taking on a greyhound! Simply, Catalina should have bypassed the M-18 and just kept the M-25 going in its early Mark II models. The M-18 was installed in so many Mark II's after replacing the 5411, and as an interim engine until the M-25 became standard.

My engine has only 513 hours on it and has been kept in tip top shape regarding maintenance. I had to replace my raw water pump (Sherman) with the Oberdorfer, due to premature shaft wear. Sherwoods suffer these days with a bad reputation. If you have the Sherwood consider the Oberdorfer as a replacement when the time comes.

So, I would not get too crazy over the lack of speed. You could go with empty water tanks and less gear to get her lighter, but the only other option is repowering. I personally do not think dropping 8K+ into an engine to achieve a few more knots is worth it.

By the way, several years ago my friend and I took his dads 1980 Catalina 30 powered by the 5411 from Destin, Florida to Mobile, Ala and back inside and outside. Under power alone we slugged along just fine against wind and tide.

Good luck

Bob

 

[noanker]

I have found my m-18 adequate for everything but pulling water skiiers. I sail because I am not in a hurry. the hull design will only allow the boat to go so fast. it is a fuel sipper that gets me where I want to go. I wouldn't upgrade to a bigger engine

 

[newboatowner]

Thanks again for all of your inputs.

I removed the prop and found that the markings indicated that it is a 12x7 which is severely undersized. That, combined with the issue of size of the engine may be the culprit. I am considering purchasing a Martec folding prop that is 14X10. The price seems ok but I am wondering if it would benefit me in thrust.

 

[Alan Gomes]

Thanks again for all of your inputs.

I removed the prop and found that the markings indicated that it is a 12x7 which is severely undersized. That, combined with the issue of size of the engine may be the culprit. I am considering purchasing a Martec folding prop that is 14X10. The price seems ok but I am wondering if it would benefit me in thrust.

I had a Martec 2-blade folder on my Catalina 30 with an M25XP engine. It pushed the boat as well as a 2-blade fixed prop. I would say that it seemed to have less thrust in reverse than the fixed, and also a good deal less prop walk. Of course, the folder will give you better performance under sail. Also, the folder does require periodic maintenance.