View Full Version : 3GM30F quesitons

06-16-2007, 11:19 PM
"Hello out there. I am hoping someone is willing to answer a couple of questions for me. I have just bought a Cascade 36 and have very little sailing or diesel experience.

I have a 3GM30F (i think, i have not found the serial # yet)that was installed as a fairly low time used engine. It has probably sat around for most of it's life (4 plus years that i know of) and has no wiring harness installed. There is a jury rigged start switch to the solenoid and a main battery cable to start it.
It is hard to start cold, but starts well when warm. I just bought two new T-125 6 volt batteries wired in series, but they don't seem to make a difference. It seems like one cylinder fires but the other two don't quite want to go. I have to use the compression release to get it to turn over with any speed. I cleaned all the battery and ground conections. It also blows black smoke under full throttle.
I know I need to buy a manual (Clymer?)but was hoping for some human help. I have been able to read some of the posts about this issue and understand fuel and compression, but don't have a clue about diesel timing or fuel richness adjusting.
I am up in the Seattle area near Port Townsend.
Also my gear box dip stick only has one mark on it about an 1/4 inch from the bottom. Do I just screw it in to check and only fill to that line? That is what is looks like, but doesn't seem to leave much room for error.
Thanks for any help anyone is willing to offer."

06-17-2007, 05:48 PM
"definately get a manual. several issues. buy the yanmar manual. they are easy to understand, and cost is not bad. can't remember who the distributor is there, but a dealer should be easy to find. can't quite figure from your post if you are having a starting problem, or a cranking problem, or both. smoke at full throttle could just be over propping. full throttle rpm. should be 3600. trying to exceed hull speed wil get you smoke. gear dipstick line is max. level. bottom of stick is min. one caution. don't, under any curcumstance, use any type of starting fluid on that engine. it will do nasty things to your pistons."

06-17-2007, 08:35 PM
"Thanks very much for the advice, Scott. I have been looking at Seloc, Clymer, and Yanmar service manual prices. About $35 for either of the first two and $85 for the Yanmar. If I read you right, the Yanmar is the way to go.
I suspect it is over propped as it will make almost 8 knots.
I am hoping at this point I just have a cranking issue. I was going to look at the contacts in the solenoid next time i get to the boat.
When i read a post about possible previous water ingestion, i became a little worried as the bottom 1/4 of the air cleaner/silencer was rotted out, mesh and foam just like it had been sitting partially submerged in water. There is also rust in the bottom third of the air cleaner cover.
Although a few friends have suggested starter fluid, I have resisted using any. I did buy a can for an emergency start, but from the great info found in this forum, it sounds like i could use WD40 for the same purpose.
Do you think i should pull the head and look around or just wait and see if the cranking issue is it? It does not turn over very fast at all and with just one set of batteries, it barely turns over at all without the compression releases open.
Thanks again, Scott, for your quick response."

06-17-2007, 10:26 PM
"yanmar manual definately worth the extra $. I don't recommend wd40 either. have seen engines damaged by that, too. try to solve cranking issue first. don't remove head just yet. check compression, injectors first. once you've reached hull speed, any more throttle will produce smoke. she won't go any faster. when you get that far, try to get an rpm. readout @ hullspeed. (if you're not sure of what that is, watch for the big, trailing wave)"

06-18-2007, 08:57 AM
"I just thought of it..
Remove the exhaust elbow, and check for carbon & soot. The goose neck type I have seen blocked solid, or a outlet restricted to a pencil dia. Clean and install with a new gasket. Yhis happens when this engine is not run under load.
good luck"

06-18-2007, 10:37 AM
"excellent suggestion. these engines very prone to that, (sooting)and could cause the hard start, too. sometimes you will see soot in exhaust water."

06-18-2007, 11:03 PM
"Thanks, Scott and Ron. Your advice means a lot to me.
I just ordered the Yanmar manual. Should have it in a week'
I found a seemingly cool gal that has access to parts. I am encouraged.
Now i just need to find the serial # to confirm which engine I am trying to take care off.

Signing up for this forum (I am somewhat paranoid of giving out personal info on the internet) is one of the better things I have done lately. Of course it would be useless with responses from people like you.

I have a gas engine compression gauge. I suppose it will not work on diesel? I suppose the manual will tell me how to check the injectors?
Thanks again, you two. beers on me if we ever meet."

06-19-2007, 10:28 AM
"No, as "gas" compression meter will not work. Example, gas is 125 psi your Yanmar diesel is 465 psi. You will need a mechanic with spedial tools to check it when the need arises.
Beside the port side of the engine where the oil filter is you will find a boss, on there will be a s/n number stamped. Then check the back plate of the sea water pump. If it has Johnson on it add the letter"E" to the s/n This is a late engine and assembled in Holland. Make note as the early and late water pump impellers are not interchangable. Engine rpm at starting is 450 rpm. Get the batteries load tested, and since the starter and alternator are King's Ransoms to replace it would be a good idea to get them serviced. ie brushes bearings & bushings. A good preventive mtce. The Yanmar Service book is a good read. The Yanmar GM series is a great engine."

06-19-2007, 08:14 PM
have seen diesel compression guages at harbor freight pretty reasonable. but you would still need an adapter. compression test should not cost all that much. probably worth while to hire it out. injectors need to come out to check compression. have them tested while they are out. (special equipment required) might take you up on those beers sometime. used to live in Point Roberts and show up now and then.

06-20-2007, 10:20 PM
"Thanks once again, Scott and Ron, for taking the time to help me out. I will certainly have the compression and injectors checked out. I guess I was planning to do it myself, but don't want to tool up for a hopefully once in the next ten years test or check. Great advice about the starter and alternator as well. I was just going to look at the contacts, but will check the bushings and brushes as well. All of this might give me a clue how many hours are on the engine.
I know how to pin back the alternator brushes for reassembly on old chevys....is there a hole for a toothpick on these yanmars?
Boat is in Sequim. I go there for 5 or 6 days about once a month. I always take a cooler...."

03-16-2008, 02:11 PM
"Hello all,

I am having an issue with my Yanmar 3GM30F that hopefully one of you can help with.

I went to my boat on Friday and fired up the engine in preparation of a day on the water yesterday. The engine ran great and I ran it long enough to warm it up then shut it down. I went back to the slip with my family yesterday and the engine acted completely differently.

First off, it was hard to get started. Once it fired up, there was a popping noise coming from the air intake every time the number one cylinder fired (almost like a backfire?). I opened and closed each of the decompression levers one at a time and when I opened the number one cylindar, the popping stopped. Do you think I have an intake valve on the number one cylindar sticking. Are you concerned with a slight film on the surface of the antifreeze when I open the cover? Also, when I started it yesterday, the plastic antifreeze reservoir overflowed hard enough to knock the lid off.

That started my mind in the direction of a head gasket allowing compression into the water jacket and compressing the fluid in the reservoir, thus blowing the lid off the reservoir. Would this cause a popping noise at the air intake? Am I thinking too much into this?

I bought the boat used so I don't know the history of the engine but it has ran like a champ since I got it and did fine during a 200 mile on-engine run from Miami.

Could it be something else? What is the fix?

Also, what grade/brand of motor oil do you suggest? I am not sure what API Service "C" is. I used what the manual suggested (30 weight).

Any advise would be appreciated, I want to go sailing.

Ray Tarr
Patrick AFB, Fl
1963 Allied Seawind, Crackertail
Hull # 25"

03-16-2008, 02:36 PM
Yes it does sound as if a head gasket has gone. Remove the head and check. Get the valves checked and ground and lapped. may as well since the head is off. Check your exhaust elbow for carbom and leaks. Some elbows are SS and down angle and others are goose necked and cast iron. Replace if warranted. Check cylinders for water marks especially the one nead the back (gear side) and check the bumping clearance of each piston. (ie height of travel to top dead centre.
Check the injectors too. The lube oil to use is a series 3 or something recomended for diesel engines. It will say that on the jug of oil you buy. We use 15W40 all year in British Columbia. Yanmar say 10W30. After 20 hours retorque the cyl head bolts. Have the valves adjusted each year to.008 thou. Good Luck Ray

Charles Pukit
05-15-2008, 02:52 PM
"Have a Yanmar 3GM30F which had been running fine. Changed oil and filter, ran engine briefly and laid it up for 2 years.

Engine cranks OK, fuel shut off. Low oil pressure won't go off while cranking. Dip stick shows oil level OK. Pulled OP sensor out and cranked engine- no oil coming out of OP sensor hole. Took oil filter off and cranked engine- only a very little dribble oil from oil filter seat. No bad noises from engine while cranking, so I assume oil pump is OK.

Any suggestions appreciated! Charlie"

05-16-2008, 04:55 PM
Solved it by decompressing the engine so it cranked faster. All OK now. Thanks. cp

05-22-2008, 09:29 AM
"Does running the 30gm to charge the batteries only, do overall harm to the engine?"

05-15-2009, 09:30 PM
"Apparently, eventually, from all that I've heard & read, as the engines like load."

05-15-2009, 10:54 PM
"hi 8 knots is okay as its a 30hp approx engine,i have a 9hp 1gm10 and it pushes my bilge keeler,23foot,wood yacht at around 6 knots,black smoke is usually fuel so do the filters as i have found the secondary filter(engine)is very smaller and can easyly become clogged and that well resticted fuel flow,as compression tester has to be diesel one as compression ratio is at lease twice that of a petrol engine,your diesel tank could be dirty if so clean,check all fuel lines and connections,check exhaust elbow for clogging and exhaust port and while you have it out check that there is no holes in inner pipe/divider inside the exhaust mixing elbow as if there is can lead to water being suck back into engine"