Interesting problem just cropped up. Just completed changing the fuel filters, fuel pump (am I the only one with "weeping" pump diaphrams?), and all engine coolant hoses (including those leading to the hot water heater) on my 1985 2GMF (H31). Bled fuel system and engine seems to run just fine except that I can't get more than about 2800 RPM in forward gear. Reverse works just fine. I made no changes in the throttle linkage. Any ideas? Thanks in advance. Smooth Sailing, Tim (S/V "TIDE")
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When is the last time you tried to give it WOT?
Tim: When is the last time you tried to give it wide open throttle? 1. Have you tried going below with the engine running and moving the throttle by hand (be careful of the belts & pullies)? 2. Have you inspected your mixing elbow? 3. Are you trying this in gear or out?
Tim: When is the last time you tried to give it wide open throttle? 1. Have you tried going below with the engine running and moving the throttle by hand (be careful of the belts & pullies)? 2. Have you inspected your mixing elbow? 3. Are you trying this in gear or out?
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Tim Leighton
STILL TROUBLESHOOTING
Steve: To answer your questions. Probably haven't tried WOT since sometime last season. Seems wierd that I get it in reverse and not forward. The mixing elbow is fine, good water flow and elbow itself stays cool (until I moved the exhaust to the the starboard aft side of the boat the only way I could confirm good SW coolant flow...what a dumb Hunter design!). Haven't tried seeing if the block throttle linkage has additional movement after I reach full throw at the helm. I'll give that a shot today and will keep you (and anyone else interested) posted. Thanks! Tim (still perplexed on the Chesapeake)
Steve: To answer your questions. Probably haven't tried WOT since sometime last season. Seems wierd that I get it in reverse and not forward. The mixing elbow is fine, good water flow and elbow itself stays cool (until I moved the exhaust to the the starboard aft side of the boat the only way I could confirm good SW coolant flow...what a dumb Hunter design!). Haven't tried seeing if the block throttle linkage has additional movement after I reach full throw at the helm. I'll give that a shot today and will keep you (and anyone else interested) posted. Thanks! Tim (still perplexed on the Chesapeake)
Have you actually removed the elbow?
Tim: I have to agree with you about this being strange. I assume that you are talking about the discharge going under the stern rather than out where you can see it. Have you actually removed the elbow to check for coking. I would do this must to make sure. It really does not make sense that this work in reverse and not in forward. Was you boat in the water all winter? Maybe you should have someone check out the prop? I'll be interested in knowing what turns up.
Tim: I have to agree with you about this being strange. I assume that you are talking about the discharge going under the stern rather than out where you can see it. Have you actually removed the elbow to check for coking. I would do this must to make sure. It really does not make sense that this work in reverse and not in forward. Was you boat in the water all winter? Maybe you should have someone check out the prop? I'll be interested in knowing what turns up.
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Ernie Rodriguez
Same problem
I have a similar situation with my Yanmar 3GM. After rebuilding the engine with new pistons,rings,cylinder sleves, connecting rod bearings (and one new connecting rod), injectors and overhauled head I find that wot is 2900 in forward underway and 3450 in neutral. I also found that tied up to the dock in forward the best I could get was 2600 in forward and 3400 in reverse. There gear ratio is different in reverse than in forward, so that is not surprising. However, just recently I decided to inspect the mixing elbow just to make sure and found some coking right at the input to the elbow. I had replaced it three years ago so I did not expect it to be a problem, neverthless after I cleaned it out with a wire brush I found that it is pitted quite bad, almost to the point that if I were to use it again it would probably start leaking from the inside. The outside of the unit looks brand new. I plan to replace it and also the waterlift muffler with a bigger one. If that doesn't get the rpms up to what it is supposed to be, looks like I will be back to square one. Anyway, in your case you really need to take a close look at that mixing elbow. Good luck with yours, Ernie
I have a similar situation with my Yanmar 3GM. After rebuilding the engine with new pistons,rings,cylinder sleves, connecting rod bearings (and one new connecting rod), injectors and overhauled head I find that wot is 2900 in forward underway and 3450 in neutral. I also found that tied up to the dock in forward the best I could get was 2600 in forward and 3400 in reverse. There gear ratio is different in reverse than in forward, so that is not surprising. However, just recently I decided to inspect the mixing elbow just to make sure and found some coking right at the input to the elbow. I had replaced it three years ago so I did not expect it to be a problem, neverthless after I cleaned it out with a wire brush I found that it is pitted quite bad, almost to the point that if I were to use it again it would probably start leaking from the inside. The outside of the unit looks brand new. I plan to replace it and also the waterlift muffler with a bigger one. If that doesn't get the rpms up to what it is supposed to be, looks like I will be back to square one. Anyway, in your case you really need to take a close look at that mixing elbow. Good luck with yours, Ernie
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Tim Leighton
WILL GIVE IT A SHOT
Hadn't thought of the mixing elbow since it remains cold when the engine is running and warm. As you are all aware, it is a bitch to remove and replace. I've been doing so every 2-3 years ever since I had to replace the darn thing about 8 years ago. Still, doing so allows me to give it a good cleaning and remove all that coking. Still, I'll probably do so....just in case! FYI, I did figure out that it is not unusual to have different max RPM's in FWD and REV. The prop is pitched for max thrust in FWD, not REV. So it makes sense that REV would run a bit faster (less blade angle = less thrust = higher potential RPM). Will continue to troubleshoot and report back here. Thanks again for all the advice. Tim (S/V "TIDE")
Hadn't thought of the mixing elbow since it remains cold when the engine is running and warm. As you are all aware, it is a bitch to remove and replace. I've been doing so every 2-3 years ever since I had to replace the darn thing about 8 years ago. Still, doing so allows me to give it a good cleaning and remove all that coking. Still, I'll probably do so....just in case! FYI, I did figure out that it is not unusual to have different max RPM's in FWD and REV. The prop is pitched for max thrust in FWD, not REV. So it makes sense that REV would run a bit faster (less blade angle = less thrust = higher potential RPM). Will continue to troubleshoot and report back here. Thanks again for all the advice. Tim (S/V "TIDE")
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