38-200 rattles

[Don Taugher]

I'm just curious, are other 38 owners bothered by rattles while idling or motoring at low RPM? I have a 38-200, the engine cover, ladder and head door all rattle at low RPM then smooth out when close to 1000 RPM. I love the wood, but it can be a bit noisey, anyone have a cure? I've added some weather stripping around the engine cover, it has helped some, but still not what I consider quite. It looks like the PO put some wedges between the teak plywood panel and the frame of the head door to stop the vibration, maybe it's time to re-wedge.

Any suggestions?

Thanks,

Don Taugher
38-200 #263
Running Free

 

[Gary Peterson]

Don,
Is the engine rattling more pronounced in gear or out of gear?
The more cylinders a diesel has the less vibration at lower speeds.
Diesels have considerably more compression than gasoline engines-hence more vibration at low speeds that can't be absorbed by the rotating mass.
Injection events, flywheel size, marine gear to flywheel coupling, and motor mount isolators play into the equation. Turbocharged diesels are smoother because of the lower compression. Vibration issues in gear could be also caused by mis-aligned shaft to marine gear, gear ratios and the number of prop blades.
I have seen masts shake because the low speed resonance values of the engine come together at slow speeds. The mount isolators couldn't absorb the produced excitements.
When we did Torsional Analysis of large diesels in yachts, sometimes the analysis produced a barred engine speed at low rpms.
Bottom line-check engine alignment, check motor mount isolators, and check with the engine selling distributor if the mount isloators have the correct rubber Durometer. I have some of the same issues in gear because I have a 2 bladed folding prop.

 

[ted_reshetiloff]

This type of problem is pretty common on boats and can be frustrating to resolve but the first place I would start is by checking out your engine mounts and engine alignment. In most E-38's I have seen including my own the mounts are attached to the stringers/grid with lag screws which will work loose over time. You can reinstall them with an adhesive (not advisable as it will be a PITA to replace), you can remove them and install threaded inserts that will accept machine threads, or you can do what I believe someone else on this board has done which is to hollow out part of the stringer to facilitate through bolting. I am not sure I am crazy about that method but having not seen the application it could be just fine. Then there is the condition of the mounts themselves. Are they old and hard? Are the soft from oil impregnation? New mounts can help to quiet that beast. After you have found the mounts and engine alignment to be satisfactory you can look at the engine insulation and how your ladder and cover are installed. The engine will always vibrate some its a diesel but you can use properly aligned latches to secure the cover from vibrating and you can use/make tight fitting catches for the ladder. On my 38 the 2 guides that hold the top of the ladder in place were held in place with small wood screws which had worked loose. Here is another place for threaded inserts. Carefully align the catches so the ladder fits tightly, but not too tightly to get it out. You may also try applying some tape like what is shown here: http://www.apsltd.com/Tree/d3000/e2131.asp

 

[u079721]

Mine too

Well I don't have any remedy to suggest, but our 1989 E38-200 would also rattle at the lowest RPM. Not enough to resort to wedges or the like, but nudging the speed up from 800 to 1000 would always even things out and make things smooth.

It didn't bother us though, because it was second nature after we started the engine to throttle down by feel to just the speed where things were smooth. I do remember though that when motoring for any length of time with the engine thoroughly warmed up this was not a problem, and we could take the throttle all the way down when going into neutral and leave it there. So we just figured it was a quirk of the boat.