1985 E26 Yanmar question

[Port Ludlow]

Hi folks,
I have always found answers to issues in this forum and currently have questions about my small 1GM 8hp Yanmar. When cold there is a few minutes of unburnt fuel(black) in the exhaust. The engine will run all day at 2500 rpms at about 4 knots. It appears to be over propped as the boat originally came with a 2 blade prop. It seems a past owner changed to a 3 blade 11-11 pitch. Does anyone know the correct prop for this boat? Also any help diagnosing the unburnt fuel and low rpms would be helpful. The engine is now 31 years old, so is it at the end of its service life? Thanks.

Bob

Cosmos Lady
E26-2

 

[Don Smith]

Bob,

Years ago I bought a used 1985 E26 with a Yanmar 1-GM. I had the opposite problem in that I could easily rev the engine with it in
gear but the prop did not seem to have much bite. I had the prop pulled with the intention of having the pitch increased. I ended up buying a new prop with slightly more pitch than the original.The receipt describes the new prop as follows: "New 12x12 2 blade 3/4 bore, R.hand sailor". That solved the problem.

I've written down the pitch number somewhere. I think it's on the boat and if I can find it, I'll let you know. Whatever pitch it is, it seems optimal.

Happy Holiday sailing.

Captain Don
Gitana, E26

 

[Mike Davis]

Hi folks,
I have always found answers to issues in this forum and currently have questions about my small 1GM 8hp Yanmar. When cold there is a few minutes of unburnt fuel(black) in the exhaust. The engine will run all day at 2500 rpms at about 4 knots. It appears to be over propped as the boat originally came with a 2 blade prop. It seems a past owner changed to a 3 blade 11-11 pitch. Does anyone know the correct prop for this boat? Also any help diagnosing the unburnt fuel and low rpms would be helpful. The engine is now 31 years old, so is it at the end of its service life? Thanks.

Bob

Cosmos Lady
E26-2

Hi Bob
We have a 28+ with a 10hp Universal. The stock prop for that is 12x12 with two blades. This fall I put a new Campbell Sailor 12x7 three blade on and it makes all the difference in the world. An 11 in. pitch for 8hp seems excessive to me.
Mike
E-28+ RUCKUS

 

[Alan Gomes]

Hi folks,
I have always found answers to issues in this forum and currently have questions about my small 1GM 8hp Yanmar. When cold there is a few minutes of unburnt fuel(black) in the exhaust. The engine will run all day at 2500 rpms at about 4 knots. It appears to be over propped as the boat originally came with a 2 blade prop. It seems a past owner changed to a 3 blade 11-11 pitch. Does anyone know the correct prop for this boat? Also any help diagnosing the unburnt fuel and low rpms would be helpful. The engine is now 31 years old, so is it at the end of its service life? Thanks.

Bob

Cosmos Lady
E26-2

Hello, Bob.
I have the same boat (a 1984) and engine as you. When you say, "the engine will run all day at 2500 rpms" do you mean that this is the maximum you can hit? If you can't hit at least 3500 rpm with that engine (in gear) then you are over propped, or else the engine is not making its rated hp for some reason. You do need to confirm the actual engine rpm with a laser tach, by the way, because the tach on that engine is almost certainly off--though it's unlikely to be off by more than a few hundred rpm. You can obtain an inexpensive laser tach from Harbor Freight.

As for the correct pitch: When you ask, "Does anyone know the correct prop for this boat?" you are asking the wrong question. The "boat" has nothing to do with the correct pitch for the prop. In order to determine the correct prop pitch a prop shop needs to know primarily: (1) the engine hp; (2) the gear reduction ratio of the transmission; (3) the number of blades. I say "primarily" because there are certain design factors unique to certain props that can require more or less pitch. For example, the Campbell-Sailer prop generally requires less pitch than a conventional prop due to the shape of the blades. But that's something that a prop shop can tell you.

The bottom line is that it is best to call a reputable prop shop in your area and have them tell you what you need. Be prepared to give the engine hp at max rpm as well as the transmission gear ratio.

By the way: I recommend the 3-blade Campbell-Sailer prop for this engine. As it is, we have a marginal amount of hp for a 5200# boat, so having an efficient prop is imperative. I originally had a 3-blade prop with big dumbo ears. It worked fine as a prop while under power but had a horrendous amount of drag under sail. The nice thing about the Campbell-Sailer prop is that it is very efficient for a 3-blade fixed prop and has much less drag under sail. With the same engine as you have, I typically motor at 5.2-5.4 knots at about 2900 rpm. This is comparable to my previous "Dumbo-eared prop" minus much of he drag. This June I'll be swapping out my 1GM for a 1GM10, which I got off of eBay for an excellent price. (It had been run only in fresh water and was rebuilt not that long ago.) The 1GM10 adds a couple of hp, which is significant when you are talking about as little hp as our engines have. I'll be sending back the prop to have a little bit of pitch added to it, in order to take advantage of the extra hp.The company that makes the Campbell-Sailer prop offers outstanding tech support and they can really answer all your prop questions. (By the way: They do spell it "Sailer" for some reason.)

For an excellent review of the Campbell-Sailer prop by the very reputable Maine Sail, see: http://forums.sailboatowners.com/index.php?threads/prop-review-campbell-sailor.112587/

 

[Alan Gomes]

Bob,

Years ago I bought a used 1985 E26 with a Yanmar 1-GM. I had the opposite problem in that I could easily rev the engine with it in
gear but the prop did not seem to have much bite. I had the prop pulled with the intention of having the pitch increased. I ended up buying a new prop with slightly more pitch than the original.The receipt describes the new prop as follows: "New 12x12 2 blade 3/4 bore, R.hand sailor". That solved the problem.

I've written down the pitch number somewhere. I think it's on the boat and if I can find it, I'll let you know. Whatever pitch it is, it seems optimal.

Happy Holiday sailing.

Captain Don
Gitana, E26

Don,

If it's a "12x12 2 blade" then it is 12" diameter and 12" pitch.

What kind of motoring speeds do you get with that? Just curious.

 

[Don Smith]

Don,

If it's a "12x12 2 blade" then it is 12" diameter and 12" pitch.

What kind of motoring speeds do you get with that? Just curious.

Alan,

It depends on the wind, current, how clean the bottom is, etc., etc.. Generally I can go 5 knots at around 2000 RPMS without any strain on the diesel.

Captain Don
Gitana E26

 

[markvone]

Don,

My Ericson brochure for the E26 with the 10hp Westerbeke says the boat came with a 12 x 10 2 blade prop.

My Ericson brochure for the E26 with the 7.5hp Yanmar 1GM says the boat also came with a 12 x 10 2 blade prop.

My 1984 E26 #205 had the 7.5hp Yanmar 1GM and would run at 6 knots at WOT at 3600 rpm easily with the factory 2 blade prop.

Mark

 

[907Juice]

I have an 82 25+ which I'm sure has the same 1gm. As far back as I can trace back, my boat maintenance log shows a 12x10 sailor. I just bought a new one this year cause the previous one was pretty worn.

As as far as being over or under propped, there are some pretty good forum discussions on how to check the tach as well as checking it out under a load. I think I just googled proper prop size and found some good info.

Juice

 

[Port Ludlow]

1985 E26 Yanmar question - follow-up

Thanks for everyone's feedback and suggestions. I have since had a Yanmar mechanic adjust the rack and the prop re-pitched from 11x11 to 11x9. Without much of an expense, the adjustment has reduced the unburnt fuel at startup and the re-pitched prop has increased the max rpms. The boat now runs 2800 rpms at 4.8 knots and will max out at 3000 rpms going 5.2 knots. Because of its age, the boat tach is off 100 rpms every 1000 as measured with a laser tach. Hopefully there will be many more miles left from this 31 year old diesel. It doesn't get any more efficient than the 1GM.
Bob

 

[Alan Gomes]

Thanks for everyone's feedback and suggestions. I have since had a Yanmar mechanic adjust the rack and the prop re-pitched from 11x11 to 11x9. Without much of an expense, the adjustment has reduced the unburnt fuel at startup and the re-pitched prop has increased the max rpms. The boat now runs 2800 rpms at 4.8 knots and will max out at 3000 rpms going 5.2 knots. Because of its age, the boat tach is off 100 rpms every 1000 as measured with a laser tach. Hopefully there will be many more miles left from this 31 year old diesel. It doesn't get any more efficient than the 1GM.
Bob

Bob,

Not to be a downer, but I wonder whether you have really solved your problem. If you can only hit 3000 rpm max you are well below what you should be able to hit--assuming that's true rpm and not merely what the tach shows. What is the actual max rpm as shown on a laser tach? You should be able to hit 3500-3600 (true), if the engine is putting out its rated hp with an appropriately pitched prop.

The Yanmar tach's inaccuracy is probably not due to the engine's age. They just are off. I have a 1GM in the boat and a 1GM10 in my garage that I'm going to swap into the boat, and both tachs are off in generally the same way. If yours is like mine, then if you are showing 3000 rpm on the tach it may be that you are getting about 3250 or so true--not enough. Again, the laser tach will tell you for sure. (They are not expensive at Harbor Freight.)

Also, the proper solution is not to simply lower the pitch on the prop without first determining whether the engine is putting out its rated HP, or something awfully close to it. If you tell a prop shop what the correct hp should be, number of blades, prop diameter, and transmission ratio, they can tell you what the pitch *should* be. What I'm getting at is, you don't want to just de-pitch the prop to accommodate an engine that has lost some of its power, because it will not perform properly. Taking a full 2 inches of pitch off of that prop should have made a really significant difference, and if you are *still* only hitting 3000 rpm (or 3250 true??) then you're treating a symptom and not the cause. A top speed of 5.2 kts is lower than you should get. I cruise at around 5.4 and can hit close to 6 if I really wind it up to 3500 rpm. My engine is the lower HP 1GM. Is yours a 1GM or a 1GM10? If it's the 1GM10 you should be doing even better still.

 

[footrope]

I agree with Alan that you may not be addressing a power issue. Have you been through your exhaust system and had the fuel injectors checked and cleaned/reconditioned? The pic shows 10 years of carbon build up in my exhaust elbow. It definitely reduced power, if not rpm. Exhaust hoses can also fail where the inner liner separates from the carcass of the hose. That can restrict the exhaust also. Maybe you have addressed these possibilities but not mentioned them in the thread?