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Adrift
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46 Posts
Discussion Starter · #1 ·
Here is what I know about the boat/engine:

-1gm10 w/410 hrs. Not sure of service history.
-boat sat from fall 2013 to May when I bought it.
-it had about 2/3 tank of diesel, I filled it in May and put fuel treatment in.
-I changed the oil, filter, tranny oil.

The engine starts and runs well, but won't rev over 2500rpm. It also surges a bit, at full throttle is remains at 2500rpm, and occasionally goes up to 3000 only to drop back down. Also, if I drop the revs, then 'gun' it, it will go above 2500 for a short time before dropping back.

I'm thinking some kind of fuel delivery problem....time to change the fuel filters? I drained the fuel filter today and fair bit of black particles came out....this also got air in the system so I know I have to bleed it next time.

Any advice/additional info. appreciated. Hoping it's not a big job!!!
 

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Adrift
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46 Posts
Discussion Starter · #3 ·
Hello. In drive.

To be honest I didnt think to do this in neutral.

The boat needs a bottom job, but was power washed and the prop was relatively clean.
 

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Remember you're a womble
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2,328 Posts
Try it in neutral as well, that'll tell you if the engine can at least rev to 3600rpm easily. Do you get any smoke when you try to push it past 2500?
Also, have you checked to see if full throttle at the lever actually gets you full throttle at the engine?
 

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Registered
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765 Posts
I had this exact problem on my old 1GM (not the 1GM10) and I changed EVERYTHING, reset timing, adjusted valves, checked compression, clean prop, nothing worked. Finally hired a mechanic who pointed an IR thermometer at the exhaust and told me it was a partially clogged. I dont remember if I fixed it before changing the engine for a 2GM13. I even borrowed a strobe light to check the speed of the flywheel to make sure the tach was reading right.
The 1GM was just too small for an 8000 lb boat cuz it had only 6.5 hp.
 

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2,569 Posts
My old Volvo MD17C has never managed to get beyond 2250 rpm when in gear.
Peak power I understand to be at 2500 rpm.
If I try to push it harder than 2250 rpm, it simply smokes a lot and there is no point.
I just live with it.
2250 rpm is about 8 and a bit knots.
Not too bad for an 11 ton ship with a long keel.
 

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Mechsmith
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240 Posts
Rocketer, you are over propped, or have a plugged exaust. If a diesel smokes more than briefly it's being overloaded. This will either "tulip" the valves or put a hole in the piston sooner or later.

I have seen it happen a couple of times in my farm equipmment repair business. It will happen when the wind is on your nose and all you want to do is get home and you won't even notice the smoke in time. Fix it! It will blow at the most inopportune time.
 
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