Yanmar 2gm20f not going over 2k rpms

Jun 11, 2019
21
Hunter 30 Port Canaveral
I just recently bought a 79 hunter 30, first sailboat ever so I'm still learning. When I first got the boat the motor would give lots of black smoke and not go over 1200rpms. Since then I have had the prop and bottom cleaned, prop and shaft were pretty bad but bottom looked clean. Also I have done fuel filters, added biocide and a stablizer to the fuel. I have done oil, oil filter, air filter, cleaned raw water strainer, all now hoses, new mixing elbow, and new belts. It now runs good , no black smoke but won't go past 2000rmps. I'm getting 5.5 knots at full throttle at the 2000rmps, no smoke at all. Any help would be appreciated
 
Jan 24, 2009
450
1981 Cherubini Hunter 27 Shipwright Harbor Marina, MD
You should post this in the Forums for All Owners > Engines & Propulsion section, it's not a Hunter specific question and you'll get more responses. Good luck with it.
 
Apr 22, 2011
865
Hunter 27 Pecan Grove, Oriental, NC
If you can get around 3500 rpm in neutral, then more than likely your problem is due to overproping. My 2gm20f has a 15x11 prop which I run at about 2500 to 2800 rpm underway.
 
Jun 11, 2019
21
Hunter 30 Port Canaveral
Ok... I'll double check when I go back the boat this weekend, but im pretty sure I only get 2000 rpm in neutral as well
 
May 27, 2004
1,964
Hunter 30_74-83 Ponce Inlet FL
I've owned a sister ship to your boat since new. PM me if you do have model specific questions.
 
Feb 8, 2014
1,300
Columbia 36 Muskegon
Could also be the throttle linkage not moving the throttle lever all the way. You can check that by disconnecting the cable from the engine and moving the lever by hand. If it goes further by hand than it did with the cable you've found the problem.
 

Jaxg

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Jun 30, 2019
20
Hunter 37 Cherubini Jacksonville
Just spoke with my neighbor 38’ Island Packet he said he had the same problem (cant break 2k) and it ended up being the prop. Took an experienced prop guy to get it dialed in but now he can do a comfy 25-2700rpm, but unfortunately only gained about 1 mph. You should be able to take a boat in neutral to its redline, if you can only get 2k in neutral, it ain’t the prop. BTW i was blown away at the amount of room in a 38’ Island Packet with 2 generous staterooms. The interior layout was done very very well. He’s about to dump it for 100k (2005 ) it would be an incredible liveaboard. I’m thinking my H37c would however leave him in my wake.
 
Jun 11, 2019
21
Hunter 30 Port Canaveral
Yea will not go past 2k rpms in neutral. Gonna recheck fuel lines and throttle linkage this weekend