Yanmar 1gm10 Performance Problem

[Tropic Cat]

Originally Posted by michaelmrc

What about injectors or a weak lift pump I've read somewhere that a weak lift pump will prevent the engine from hitting max revs
If it was prop related wouldn't it happen all the time

I have two of these engines in my boat. First, I'd like to know what the diameter and the pitch is on the new 3 bladed prop.

Next, I'll suggest you change both fuel filters and follow the Yanar directions to the letter when bleeding the fuel lines.

Lastly, get in the water and look at the prop. Bring a scraper with you and clean it.

If that doesn't do it, then go deeper into the issue. It sounds like you're making this more complicated than you need to.

[michaelmrc]

Originally Posted by Chief Engineer

Who specced the three blade prop for a one cylinder engine?

Chief the prop was recommended by northbywest propellers And Ron Campbell maker of Campbell sailor props

[michaelmrc]

Originally Posted by Tropic Cat

I have two of these engines in my boat. First, I'd like to know what the diameter and the pitch is on the new 3 bladed prop.

Next, I'll suggest you change both fuel filters and follow the Yanar directions to the letter when bleeding the fuel lines.

Lastly, get in the water and look at the prop. Bring a scraper with you and clean it.

If that doesn't do it, then go deeper into the issue. It sounds like you're making this more complicated than you need to.

Will do for sure I've changed the secondary filter already and just picked up the new primary filter today so will get down there this week and change it out
Question though when a diver cleans the bottom of your boat don't they normally do the prop as well

[michaelmrc]

oh and the campbell sailor prop is one that ron campbell has used successfully on several 1gm installs. is a 12" diameter x 7" pitch

[Tropic Cat]

The prop should be sized so the engine turns 3600 RPM at full throttle in forward gear. Like the Chief, I've never heard of a 3 blade prop in a 1GM10. But having said that the size and the pitch sound right.

I'll place my bet's on that filter.

[michaelmrc]

Let's hope would be happy if it was that simple

[michaelmrc]

well update to the dilemma this weekend i changed the primary filter rebled the system dove under the boat cleaned the prop prop shaft hull etc.. (note it wasnt very dirty just a little fuzz) and yet the engine still doesnt run up past 3000, yet if i put it in reverse it will rev up to 3500 no problem. under forward only 27 -2900. i cant see it being the prop i checked it for any dings or damage didnt find any and it used to rev to 3200 no problem before. what else can this be any suggestions as to the next place to troubleshoot. thanks everyone. ..... frustrating

[Ex-Calif]

Any smoke or crud coming out of the exhaust?

I would expect that the engine will rev higher in reverse than in forward due to prop geometry. I presume you are doing these tests while tied to a dock. If so I would expect max rpm to be a little lower than redline because the prop and engine are under a higher load when static.

I will further presume that in neutral you can achieve static (redline) rpm. This proves the engine is not being governed to a lower rpm but does not indicate if the engine will make rated hp.

Less than max RPM loaded with no smoke = lack of fuel
Less than max rpm loaded with smoke = restriction or overload

You state that you have had a "lower" than 3600 speed since the new prop was installed. This indicates the prop is slightly oversized for the boat. However, you probably still pushed the throttle to max to get max speed.

What I suspect happened fro the point you changed the prop is that you weren't getting complete combustion at WOT and you have been slowly coking up the exhaust mixer. It is a slow and insidious process.

You checked "up the tailpipe" but you haven't checked the exhaust mixer.

My two recommendations are

- pull the exhaust mixer and check it
- have the injectors cleaned.

[captain58sailin]

Wouldn't hurt to take a look at your packing gland, make sure you are getting a little drip coming through. Just sounds like you might have too much load on the engine somewhere, perhaps the prop is over sized/pitched for the engine/vessel combination, even pros can make mistakes sometimes. The exhaust mixer could also be the culprit.

[michaelmrc]

ex-calif thank you that does make sense. i dont get any black smoke while running wot but with my old 2 blade prop i could obtain 3600 rpm in forward although it didnt have the torque that this one does. and yes when i get to 3200 rpm my throttle is only at about 2/3s open but i typically push the throttle to wot and as you mentioned i havent checked the exhaust side of the mixer i will pull it off and take a look. if it is all coked up is there a preferred method of cleaning it. as well will i need a new gasket or can i use the old one with some sealant.

captain58sailin i have checked the shaft and packing gland to make sure things were smooth thanks i will check the exhaust mixer.

[Ex-Calif]

Ironically, I currently have this problem. I hear that you can't clean them but I also hear that you can. I am going to find a local shop here with some nasty chemicals and see if they can give it a shot.

I have also priced a new one at around $400.

[michaelmrc]

ok another update, last night i changed the primary filter had a hell of a time bleeding the system but everything seemed ok. today i took it out it ran at 3300 rpm and didnt miss a beat. i killed the engine sailed for a couple of hours then fired it back up to return to the marina. put it in gear wot 2700 slowly creeping up to 2900 with the engine running i rebled the injector and as i cracked the screw air came out and the engine reved up to around 3100 once back at the dock i pulled off the exhaust mixer tube to see if it was coked up. other than a little normal soot it seemed just like new.
so not filters, not the exhaust tube not the prop whats my next step .....

[Ex-Calif]

So you've been able to duplicate the 3200-3300 RPM you always had since changing the prop.

After a period of idleness you got 2700 creeping to 2900 until you bled the injector while running.

Doesn't it appear air is getting into the high pressure side of the fuel system?

[Tropic Cat]

Originally Posted by michaelmrc

just had a diver about a month ago clean the bottom he did mention that im due for bottom paint though. when i left last weekend the boat ran pretty consistent at 3200 with the occasional drop to about 3000 which i assumed was the alternator kicking in charging batteries. but when i returned from this trip it started out at about 2500 slowly crept up to about 2800 but wouldnt go any higher.

What next step. You just wrote that your engine is back up to where you said it was.

Be Happy

[michaelmrc]

well im not sure thats its fixed. like i said it started to drop in rpms and only seemed to recover once i bled that injector.