detriot 671 tib not hitting no load rpm

[captcrunch]

Finally had my mechanic out on the boat yesterday, as
I have been having an Issue where the boat will run great then appear to bog.

He discovered I am not hitting no load rpm on the starboard motor an have a lot o crank case blow by. he is going to take the boat Monday to start working on this, anyone have any thoughts as to hat can be causing this an fixes? from t I've read so far sounds like I could be talking a rebuild

 

[oscarvan]

Lots of possibilities.... start with valve adjustment and check the rack and make sure all injectors are on the same page. Then look at compression issues..... cylinder walls/rings/valves.... Remember that individual jugs can be re-lined in situ, although if one is tired the other ones may not be far behind. And, the head can be pulled for a refurb.... No need to declare it deceased just yet.....

He will most likely do a compression check and take it from there.

 

[kingsley_oasis]

Unless motor is really trashed or starved of fuel it should hit no load rpm. You would also expect noticeable misfiring. No load rpm being low is usually linkage not fully traveling, or governor adjustment.
Now if you mean WOT under full load, then that is a different story

 

[JD5652]

If you have signifcant blow by that means the rings need to be replaced on those cylinders. You could also try a top end tune up meaning injector height adjustment, governor adjustment, rack adjustment.

How bad is the blow by?? How many cylinders?

 

[captcrunch]

Don’t have that info yet, hoping it as something like a governor or linkage adjustment and not bad rings. Engine took a hit two years ago sucking up exhaust from the port motor

 

[oscarvan]

Engine took a hit two years ago sucking up exhaust from the port motor

What happened here?

 

[captcrunch]

Marmon clamp broke on port motor and starboard infested a ton of exhaust gases, blower was carboned up etc and was replaced along with all the exhaust leaks sorted. Interesting I had the throttle cable on the starboard motor replaced a few seasons ago right before all this happened and it’s been a long road sorting through exhaust leaks and such so sort of hoping that it may be a linkage or governor adjustment.

 

[Finalee]

I've seen worn out diesel and gas motors still able to hit high idle rpm. Now starting them was a different story. Check the easy stuff first.

 

[Bob Bradley]

Probably a silly question, but have you disconnected the throttle control cables and tried to move it to full throttle by hand?

 

[captcrunch]

Have not tried that yet. Going down to the boat this morning and will look at that

 

[Dan Mapes]

Make sure the shut down lever is fully seated.

 

[captcrunch]

Adjusted throttle cable, got no load rpm. Went for bay test boat started shaking violently. Mechanic took quick look back at dock, had my shift tranny didn't like the way the years sounded.... hopefully will know mo're tomororw

 

[Briankinley2004]

Just curious if fuel supply has been checked? Are filters clean, lines unobstructed and pick up tubes clean? Perhaps try running on a different tank. Are all valves fully open?

 

[captcrunch]

Fuel system was checked, filters changed and only single tank. Port engine runs great

 

[Finalee]

Hows the bottom and running gear? Reading over the scant information it sounds like the boat has been sitting unused for awhile?

 

[rustybucket]

Adjusted throttle cable, got no load rpm. Went for bay test boat started shaking violently. Mechanic took quick look back at dock, had my shift tranny didn't like the way the years sounded.... hopefully will know mo're tomororw

Any clues as to what was shaking? Engine? Trans? Shaft wobble? What rpm was it shaking? How clean is the prop? Long shot but you could have picked up a rope or debris on the seatrial.

Given the limited info, I'd probably dive the prop to check the simplest, most likely source of vibration first (we regularly pickup stuff on the prop, like almost every trip).

Next I'd check shaft wobble, bent shaft would demonstrate bad vibrations.

High idle at the dock again to rule out the engine as source of vibration.

Once you eliminate those the trans is the next order of bidness and that's above my pay grade.