How fast does your Cherubini motor?

[TooCoys]

I've got a 1980 27' with a Yanmar 1gm10 in it, and it motors extremely slow.

We took it out yesterday for its first test sail since I bought it, and we were being passed by other sail boats left and right. It took us a good 30 minutes to go maybe 1nm?!?

I know that my cutless bearing is loose and will need to be replaced, which I plan on doing next month, but what else could be causing this?

Could the prop be slipping? At one point we though we were dragging bottom because we could hear and feel some vibration, but we were in at least 10 feet of water and I only draft 4.3'. We determined that the prop was turning because of the current as we down wave since the wind was behind us. Is that normal?

People keep telling me that sailing is just slow and that I am just not used to it, but when other boats my size are passing me, I'm starting to get concerned.

How fast does your boat go under motor?

 

[David in Sandusky]

Our '77 h27 with a 1GM10 installed 8 years ago will motor at 5.5 to 6 knots in relatively calm conditions. (That is when there is not enough wind to sail!)

What rpm do you get in neutral gear with a wide open throttle? The spec is 3,600. 3,300 to 3,600 is OK. If you can't make those rpms in neutral, then you have a problem with your fuel or air supply, or your exhaust system may be blocked.

If you get over 3,300 in neutral, then what are your rpms at wide open throttle in forward gear? What does your exhaust look like? (Clear, cloudy, black, or white?) Again, you should be able to turn at least 3,300 rpm in gear. If you can't, then your problem could be alignment ( likely because of the vibration you report), you transmission, or too much pitch on your prop.

Finally, tell us about your prop. How many blades? Fixed or folding? What are the diameter and pitch? (These may be stamped on the shaft of the prop itself - something like 13x9 or similar.) Yes, your prop could be slipping, that is one of many possibilities.

This is all stuff you will need to learn anyway. But, it is key to understanding where to look for your problem.

 

[TooCoys]

Our '77 h27 with a 1GM10 installed 8 years ago will motor at 5.5 to 6 knots in relatively calm conditions. (That is when there is not enough wind to sail!)

What rpm do you get in neutral gear with a wide open throttle? The spec is 3,600. 3,300 to 3,600 is OK. If you can't make those rpms in neutral, then you have a problem with your fuel or air supply, or your exhaust system may be blocked.

If you get over 3,300 in neutral, then what are your rpms at wide open throttle in forward gear? What does your exhaust look like? (Clear, cloudy, black, or white?) Again, you should be able to turn at least 3,300 rpm in gear. If you can't, then your problem could be alignment ( likely because of the vibration you report), you transmission, or too much pitch on your prop.

Finally, tell us about your prop. How many blades? Fixed or folding? What are the diameter and pitch? (These may be stamped on the shaft of the prop itself - something like 13x9 or similar.)

This is all stuff you will need to learn anyway. But, it is key to understanding where to look for your problem.

I have no idea what my RPM's are. I do not have a tach - I do not have a fuel gauge either. I have not seen any smoke coming from the engine anywhere, and the water outlet is intermittent. It will dump a bunch of water, then a few seconds passes, and then it dumps more.

This is what my prop looks like.

 

[David in Sandusky]

Looks like the original prop. Can't see any issues, but that doesn't mean very much.

Good news about your exhaust. Black could mean you are over propped, and white means a blown head gasket.

I defer to others on diagnostic tach solutions. It's strange that you don't have the standard 1GM10 instrument panel, but your 1GM10 was an upgrade. All of the h27's of our design shipped with Yanmar SB8's, or gasoline engines.

 

[TooCoys]

Looks like the original prop. Can't see any issues, but that doesn't mean very much.

Good news about your exhaust. Black could mean you are over propped, and white means a blown head gasket.

I defer to others on diagnostic tach solutions. It's strange that you don't have the standard 1GM10 instrument panel, but your 1GM10 was an upgrade. All of the h27's of our design shipped with Yanmar SB8's, or gasoline engines.

It used to have a gas engine I believe. It was changed to a diesel somewhere in the late 2000's. 2005-6 maybe.

I'd like to add a tach, but its beyond my mechanical abilities unless I can find a good set of instructions somewhere.

 

[GorillaToast]

Two years ago I couldn't get any forward speed out of my 1GM even tho the rpms were in the 3300 - 3600 range. Turned out to be a slipping cone clutch in the transmission. I rebuilt mine, lapping the cones in the process, and now I get 5.5 - 6kts in calm waters. If you're not mechanically experienced, I would advise having a shop do the work as its a bit tricky.
One way to find out if it's slipping is to start motoring and push down hard on your shift lever and see if your speed picks up.

 

[David in Sandusky]

There is a standard control panel (or two) for the 1GM10 with a tach and other useful instruments. It will come with a wiring diagram.

Is there a diesel mechanic in your area? He could be a big help, and could recommend solutions for you.

Where are your ignition and shifter mounted?

 

[TooCoys]

There is a standard control panel (or two) for the 1GM10 with a tach and other useful instruments. It will come with a wiring diagram.

Is there a diesel mechanic in your area? He could be a big help, and could recommend solutions for you.

Where are your ignition and shifter mounted?

It's mounted on the starboard side of the cockpit.

The yanmar manual says that there is a tach sensor on the back of my engine. Its on page 12 or 13. I took a photo and noticed that I have what it describes. There is a orange and blue wire coming out of it. On the other end of the wiring harness there is an unused plug that also has a blue and orange wire. I wonder if this is a simple connection.

 

[Jalepeno]

I installed one of these ten years ago. Simple, reliable, cost effective and works great.
https://www.tinytach.com/diesel-tinytach