671 ?

[neilinov]

While test running a boat the other day the engines would come all the way up at idle. When we put a load on them and started bringing them up to full speed one engine bogged down at about 1600 and never felt like it was quite putting out the same as the other engine. There was no smoke or anything it just didn't feel right. I'm not a mechanic and this is the best I can describe the situation. The owner said it was because it was chilly outside and the engine would act right as soon as it warmed up some more. We ran it for an hour and it never really straightened out. Should I walk away or is this a problem that can be somewhat easily remedied and negotiated out of the buying price?

[jimbo62]

How does it run above 1600? These engines seem to like to run between 1800 and 1950 but dont do well below that. If they run ok at 80% of max, there may not be a big issue.

[Storm]

How chilly was it?

The symptoms you describe (bogging down) could be cold/fozen fuel or a frozen or dirty fuel dirty fuel filter or a number of other issues. If the temp has been in the single digits and the engine hasn't been run for awhile, the first thing I would look for is water in the fuel filter or in the separator. Although, you should have noticed some improvement if you ran the engines for an hour. That should be sufficient time for things to thaw.

Storm

[JD5652]

While test running a boat the other day the engines would come all the way up at idle. When we put a load on them and started bringing them up to full speed one engine bogged down at about 1600 and never felt like it was quite putting out the same as the other engine. There was no smoke or anything it just didn't feel right. I'm not a mechanic and this is the best I can describe the situation. The owner said it was because it was chilly outside and the engine would act right as soon as it warmed up some more. We ran it for an hour and it never really straightened out. Should I walk away or is this a problem that can be somewhat easily remedied and negotiated out of the buying price?

Neil-

A little more info is required......

(1) Did the engine EVER get above 1600 RPM?
(2) Do you have any more data....engine temps? Turbo boost? Exhaust Gas Temps (EGT)?
(3) What was the outside temps?

Regardless, the engines should make approximately 2650 Max RPM WOT unloaded at the dock. Underway, the engines should make 2500 RPM WOT.

The owners statement doesn't make sense. I've ran my boat in 30 degree weather (J&T 671-TI's) with no problems.

[neilinov]

I'm gonna pass on this one. Something was telling me that there was something not right here. As far as the temps go, cold is a relative word. It was a "chilly" 50 degree south Florida day. I suspect it was a fuel problem, but not knowing a lot about these engines I was not sure. I've heard on more than one occasion that the 671 with the boosted up hp won't run as long in between overhauls. Any thoughts???

[Storm]

Fifty degrees. Heck, my engine would probably overheat if it ever got that hot here in Maine. Definitely not a freezing problem, but I still think it's a fuel issue.

Storm

[seapower]

it's usually right. Too many good boat's around to be buying a "maybe". Just my opinion. As to your second point, generally you will not get the hour's out of a "high output" version of any engine. You pay for power, one way or the other. Frank,SeaPower

[Avenger]

I'll second the probability of a fuel supply problem.

If it's temperature related, why doesn't it affect the other engine?

And yes, the TIB at what, 485 HP, is not notorious for long term durability.

[Storm]

I think temp-related has been ruled out. But, both engines probably have individual water separators and fuel filters. That's why one might be affected and the other not. In extreme weather conditions, a restriction can occur in fuel delivery to one engine and not the other. Or for that matter, one engine might simply have a dirty fuel filter, injector issues, fuel line could be collapsing, or a myriad of other causes.

Storm