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1GM10 yanmar diesel

Feb 29, 2020
6
O'Day O'Day 26 Baltimore
I am looking for some advice for an 1986 O'Day 26 with a Yanmar 1GM10 (C) which I bought last Fall. The engine (2008) ran away ( not over 3500 rpm) and we think the block may well have a crack. After careful inspection wear limits etc. , we rebuilt the engine and it still ran away. 1. Is it possible that the breather is causing this? It seems a very simple mechanism. 2. If not, are new blocks or remanufactured Yanmar 1GM 10 engines available? 3. Has anyone repowered an O'Day 26 with a new diesel? I am 76 now and have dreamed all my life of having a sailboat like this. I have spent the last year fixing the trailer and boat and do really appreciate your advice. I am naming the boat Solar Harvest.
 
Nov 22, 2011
960
Ericson 26-2 San Pedro, CA
I am looking for some advice for an 1986 O'Day 26 with a Yanmar 1GM10 (C) which I bought last Fall. The engine (2008) ran away ( not over 3500 rpm) and we think the block may well have a crack. After careful inspection wear limits etc. , we rebuilt the engine and it still ran away. 1. Is it possible that the breather is causing this? It seems a very simple mechanism. 2. If not, are new blocks or remanufactured Yanmar 1GM 10 engines available? 3. Has anyone repowered an O'Day 26 with a new diesel? I am 76 now and have dreamed all my life of having a sailboat like this. I have spent the last year fixing the trailer and boat and do really appreciate your advice. I am naming the boat Solar Harvest.
Not sure I have advice on the cause of the runaway, but if you did not run it over 3500 rpm that is certainly within spec for that engine and ought not to have damaged it.

I am wondering if you have an issue with the governor or the fuel rack or something of that sort? I will say that the 1GM10 is a very simple and reliable engine.
 
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Nov 6, 2006
9,209
Hunter 34 Mandeville Louisiana
I agree with Alan, Carefully check the linkage, fuel rack and governor..
 
Nov 22, 2011
960
Ericson 26-2 San Pedro, CA
I agree with Alan, Carefully check the linkage, fuel rack and governor..
If the issue does or might relate to the governor, I think I'd suggest calling in a knowledgeable mechanic, preferably someone with specific experience on engines such as yours. While the mechanical governor in the 1GM is not exactly insanely complicated, I would say that it's not the simplest system on that engine, either.

I wouldn't be too quick to give up on your little Yanmar. As I said, it's a good engine. I think a good mechanic should be able to get to the bottom of this runaway issue, and once he does I'll bet you'll be in fine shape.
 
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Nov 22, 2011
960
Ericson 26-2 San Pedro, CA
By the way: here is a quick overview of how the governor works on a 1GM10, as best I understand it. This may be more detail than you want, but I offer it for your interest. Do with it what you will. :)

The injection fuel pump has a "rack," which is like a slider/throttle that allows more or less flow of fuel depending on how far it is slid in the open direction. The position of this fuel rack depends on opposing spring pressures. On the one hand, there is a throttle spring that wants to open the fuel rack, while the governor spring opposes that and wants to close the rack.

The governor, for its part, provides the spring pressure that closes the rack as follows. When the engine starts and spins up, two weights fly outward through centrifugal force. These weights in turn are linked to a cone-like device that shoves forward on a spline, which in turn provides the spring pressure to close the rack.

When the engine is off and the throttle is in neutral, the rack is actually all the way opened and therefore prepared to output maximum fuel. However, in neutral there is also very little throttle spring pressure holding that rack opened. Of course, very little spring pressure is needed to do so because there is no pressure countering it. When the engine starts and begins its rotation, the governor kicks in and opposes the small amount of throttle spring pressure holding the rack open with a relatively larger amount of spring pressure from the governor via the engine rotation, with the net result that the rack slides in a direction to reduce the amount of fuel and lessening the engine speed.

When the throttle lever is slid forward, this tightens the throttle spring which opens the rack, giving the injector more fuel. But as the injector gets more fuel, the engine runs faster, which throws the governor weights out more because of the increased centrifugal force, which adds to the spring pressure on the part of the governor that slides the fuel rack in the direction of less fuel. It is the balancing act or stasis between the spring pressure increasing the fuel (via the throttle spring) vs. the spring pressure decreasing the amount of fuel (via the governor spring) that maintains a particular rpm.

The injector control shaft adjustment puts a hard limit on the travel of the rack, such that it can only open so far and thus only deliver so much fuel. Screwing out the injector control shaft increases the range of travel on the rack, thus allowing more fuel on the top end, while screwing it in restricts the range of travel, limiting the maximum amount of fuel the injector pump can provide.

I think from this that you could imagine that an issue with one of the springs might result in a runaway condition. Anyway, just more grist for your mill.
 
Feb 29, 2020
6
O'Day O'Day 26 Baltimore
dmax,Alan Gomes, and Kloudie1: Thank you very much guys. My son will be very interested in checking this. I am very appreciative of your help.
 
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Jul 30, 2019
208
Seaward 25 777 Fort St. James
If it stops increasing its revs at some point (3500 rpm you seem to say), then it is not a runaway as I understand them. In a true runaway the crescendo continues to the point of destruction unless completely starved of oxygen. Much more likely to be a linkage or spring problem. Get a diesel mechanic to look at it, where it is, in the boat.
 
Feb 29, 2020
6
O'Day O'Day 26 Baltimore
Noodat Lady: The first time this happened the air filter was not attached. My son, who is a mechanic but not familiar with marine engines, was squatting by the stbd. side of the engine and put his hand over the intake flange and lifted up on the decompression lever. His hand did not make out well but is ok now. There is of course more to this story, but he plans to do a compression test next. Thanks very much for your thoughtful comment. You are of course correct it would have blown apart possibly with injuries'. I will post the results.
 
Jul 30, 2019
208
Seaward 25 777 Fort St. James
Noodat Lady: The first time this happened the air filter was not attached. My son, who is a mechanic but not familiar with marine engines, was squatting by the stbd. side of the engine and put his hand over the intake flange and lifted up on the decompression lever. His hand did not make out well but is ok now. There is of course more to this story, but he plans to do a compression test next. Thanks very much for your thoughtful comment. You are of course correct it would have blown apart possibly with injuries'. I will post the results.
Wow! He's lucky it was a single cylinder, small diesel! So you are saying that except for his prompt, if possibly ill advised, action, it would have continued to increase revs, so sounding much more like a true runaway, with your original hypothesis of a cracked block seeming very likely. Your son may well have saved the boat at the cost of his injury, since conrods have been known to fly out at ballistic speeds from runaway diesels.

It will be interesting to hear the solution, and I hope it is not too expensive a one.
 
Feb 29, 2020
6
O'Day O'Day 26 Baltimore
Alan Gomes and Noondat Lady: We tried running the engine again and the RPMs went up to 3000 but no higher. We had been all ready to cover the air intake flange with a flat putty knife and pull the decompression lever. neither was necessary. We shut the fuel off and the engine stopped. SOOO... your idea about the governor seemed really good at this point. We read again and re-read the manual and looked in the oil fill port and could see the two springs, control levelers, and rack on the bottom of the fuel injection pump. We really could not see well so we decided to pull the engine up into the cabin again (UGH). Getting a better look in the cabin, we realized the rack on the fuel injection pump would not move. The rack is very small light metal working on a worm gear inside the pump to set fuel load. We tapped very lightly on the edge of the rack and it began to move very easily and we saw some dirt as well. We removed the injection pump and shim (gasket) measured .013. The pump is at a specialist being serviced and we have ordered a "shim set" for the pump from Yanmar.

This all started last fall when I hooked up a garden hose (40 lb) to the water inlet instead of letting the impeller, through suction, draw the correct amount of water into the engine to flush it out. I had also added rv antifreeze so I guess that is why I did not crack the block. In the spring , when I tried to turn over the engine with hose connected, it would not turn over( the cylinder was full of water). We hand cranked the engine and were able to start it as described above after that. We are now hanging a bucket over the stern and the engine is drawing water from that. I am not sure of all the causes and effects. I am sure I should have read the manual (always) first. The broken oil ring caused the engine to run away. After the first repair, the jammed rack caused us to think that the engine was running away again. Consulting the forum was a very good idea!! Thank you very much gents. We really appreciate it. Red Rover 1425
 
Nov 22, 2011
960
Ericson 26-2 San Pedro, CA
Please report back after you get your pump back from being refurbished. Hopefully that's going to solve your problem.
 
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Jun 3, 2004
89
Oday 26 Lake Keowee,SC
a lot of fork lifts use this engine. you can check with one in your area, same for parts
 
Feb 29, 2020
6
O'Day O'Day 26 Baltimore
Alan Gomes, Noodat Lady, and Kloudie 1: I would like to thank you fellows again for your help. It really made the difference. I have been working on other projects in the boat and otherwise and the virus slowed everything down as well. The port side chain plates and deck were a big repair with a lot of rotten wood and water intrusion. My son had covid in Feb of 2020 but did not get very sick. This past Feburary he caught it again and was very sick for 2 weeks. He is getting better now.

Refurbished Fuel injection pump was replaced. Ran the engine a few weeks ago, still hard to start, for only 15 minutes as we had honed the cylinder with changing the rings and bearings. I pumped the 15 gal fuel tank as dry as I could, refilled, changed oil and filter, and fuel filter. All the hoses were replaced as most were probably from 1986. changed the fuel pump as well. Primed the engine and started same. I slowly brought the RPM's over ten minutes to 3200 and ran that way for 20 minutes. The top rpm's was 3450 and idle about 900. we adjusted that once but that seems close enough. The engine started the next day without hesitation. Of course the prop was not engaged. I had planned to raise the mast myself and watched all the video on line about that. I have the boat positioned under a tree level on the trailer and block and tackle but I have chickened out on that for this year. The Marina wants $400 to raise it. I have just ordered new stays and shrouds and and hoping for a July launch. I will single hand most of the time and have a new question. Has anyone thought of a way to stop the Yanmar when you fall overboard? Would it have to be electronic? Perhaps a spring loaded pull that you detach as you leave that would pull the wire to stop the fuel flow?
 
Jun 3, 2004
89
Oday 26 Lake Keowee,SC
Just info.... 1GM engines are also used in forklifts. I got parts from a forklift dealer one time and they have a lot if knowledge
.
 

Ward H

.
Nov 7, 2011
3,096
Catalina 30 Mk II Barnegat, NJ
Has anyone thought of a way to stop the Yanmar when you fall overboard?
Just don't! What about if you're under sail? Consider falling overboard the same as falling off a 100' cliff.
Invest in a harness and tether. Then identify attachment points for the tether that will let you work at the mast or bow BUT will not let you fall overboard and be dragged. Even attachment points in the cockpit would be good in rough weather.

On my 82 O'day 25, basically same boat but with outboard, I ran halyard and reef lines back to the cockpit. I also had roller furling. While I wasn't afraid of working on the deck I tried to minimize doing so to reduce risk.

I lowered my mast once. Three guys and it was a struggle to lower it under control. Paying the yard to raise it is a wise move.

As you posted a month ago you were hoping for a July launch, I'm hoping you're on the water and enjoying the summer.
 
Jan 30, 2012
1,089
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Redrover

Kloudie and Alan have probably identified the problem. When the high pressure pump is installed the governor actuation fork must engage the rack - the rack must move with nearly no resistance by the way. From what you describe the pump rack pin was not engaged in the fork - setting probably forward of the crotch in the fork.

Review Ch. 4 in the Yanmar shop manual (the GM series manual) which describes how the items need to engage one another. If you don't have the manual let us know and I will see to it you get a copy.

Charles
 
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