Engine Alignment Pointers Please . .

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C

Clark

I have some pretty strong vibrations above 22-2400 rpm in a 1996 H280 w/ 2GM20F and rattles your teeth at 3000. I've read all the archives and feel as though I can do an alignment but am not sure what to expect on a few of the points. The Hunter manual says: 1) "Establish the shaft in the center of the shaft log (stuffing box assembly?) by raising the shaft until it touches the top of the log . . . . lower the shaft until it touches the bottom of the log . . . etc" Q: How much play should I see here; 1/8", 1/4", 1/2" . . . ? 2) "Now adjust the engine mounts to allow the pilot on the coupling halves to slip together . . . " Q: Will the shaft flange move very far back away from the trans flange? Is the pilot in the center of the flange(s)? The rest is pretty straightforward regarding the gap tolerance between flanges. Q: Are the bolts for the flanges and engine mounts metric? Q: What tools are used for horizontal adjustments? Seems like getting .004 would be pretty hard by adjusting the base of the mounts? Thanks all for your patience and help.
 
B

Benny

Excessive vibration?

Make sure the prop and shaft are clean and the sacrificial Zink is whole. Check for excessive play in the cutlass bearing. Replace air and fuel filter and clean water separator. A clean running engine has reduced vibration. If still excessive then you can attempt to re-align the engine. Shaft ends alingment is in the order of a maximum of 0.2 mm. First check tolerances for existing alingment. If alingment is OK then damaged or tired motor mounts are the problem. The stern tube is also responsible for controlling vibration. If replacing do all and be aware that the front and back are different and engine model specific for Yanmars. The motor mounts have jack nuts under the motor bracket and these are used to perform the adjustments. If re-alignment results in no improvement then replace the mounts. These small engines usually show marked vibration at certain rpm and as they age they loosen up increasing the vibration at those points. Yes the nuts should be metric.
 
C

Clark

Thanks Benny; follow-up ? (as usual) . .

"Shaft ends alingment is in the order of a maximum of 0.2 mm" - I take it that is the final tolerance. When the flanges are disconnected, how much total play is there? I've read that slipping a block of wood under the shaft to hold it in position is workeable and I wonder how tough it'll be to center the shaft end. I spotted the jack nuts and am aware of their vertical adjustment function. It is the horizontal adjustment that concerns me. Whack the bracket w/ a hammer?!
 
Sep 9, 2005
61
- - St Joseph, MI
Engine Alignment

I didn't know zilch about alignment, now I have more info than I can understand w/o spending time to study. I appreciate all of the above. We bought our H30 last year, the surveyor discovered the shaft to be bent .030, enough to rattle your bones. No visible damage to either prop or shaft. We concluded that a yard had lifted the boat with a sling under the shaft. Have since replaced the shaft and the missing aft "LIFT HERE" decals. Greatly reduced vibration too!
 

Clark

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Jun 30, 2004
886
Hunter 280 Lake Guntersville, AL
Yea, that is one of the things that could cause .

bad vibes and cost several boat units to address. I found a loose lock nut on one mount and it did improve my situation but not enough IMHO. I plan to do an alignment and hope that is the source of my problem. I'll also make measurements and post them here for future reference.
 
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