Twin DD 6-71, one harder to cold start

[rangernor]

I have twin 6-71 naturals in my 38 Hatteras.

They have about 1300 hours on them. Starbord engine starts very easy, with next to none smoke. The other engine
takes a couple of tries, with about 5 to 10 seconds on the starter. When it starts it puffs a big white smokecloud, but
clears after 2 seconds.

Both engines has steady idle, and no vibrations. Both never get any hotter than 175, even at WOT.

When warm, they both start by just looking at the starter button.

Any ideas what issues I might have?

[Boatsb]

I have twin 6-71 naturals in my 38 Hatteras.

They have about 1300 hours on them. Starbord engine starts very easy, with next to none smoke. The other engine
takes a couple of tries, with about 5 to 10 seconds on the starter. When it starts it puffs a big white smokecloud, but
clears after 2 seconds.

Both engines has steady idle, and no vibrations. Both never get any hotter than 175, even at WOT.

When warm, they both start by just looking at the starter button.

Any ideas what issues I might have?

That's a bit short of a history.

Tune ups and compression tests?
Injectors, fuel filters and injectors, wot rpm?

[rangernor]

No compression test. Starts very easy when warm, and no blue smoke. No smoke when warm, and 2 seconds smoke when cold.

Havent touched fuel rack, and didnt change fuel filter this year. I have additional twin Separ fuel filters also.

WOT rpm in gear are 2400 for starbord engine, and 2300 for port engine. Pulls stronge all the way up, with no hicups.

[Regal2800]

hard starts when cold and smoke are indications of low compression. how long does the smoke last on the port engine when cold?

[rangernor]

When cold start, the port engine puffs one large white smokecloud. After 2 seconds it clears, and idle is smooth.
Starts very easy with no smoke when warm.

[Regal2800]

could be one cylinder with low compression or possibly a bad injector. might also need to adjust the rack. i would call detroit mechanic and have him come to the boat if the port engine is smoking substantially more than the starboard. Smoke on cold starts could be a host of things. Also i would try to find out what the loaded RPM is on your engine. My JT 6-71n had a loaded of 2500 rpm. You might not be reaching full rated RPM which should be addressed as well.

I had 6-71N in my last boat and there was only a trace of smoke on cold starts.

[Timeout]

The battery on the hard start side may be a little weaker or loose battery connection. I once had an issue where ground wire wasn't as tight as it should be so that side cranked a little slower.

[Doug.T]

I have a similar problem with my port 6V92. Hard to start and smokes when cold. In addition, it gets hot at WOT after 5 min. Both engines pull well and have same RPMs at WOT. Water coming from the port engine has twice the rise as Stbd. 70->90 vs 70->80. Diesel mechanic friend suspects dirty injectors. Any thoughts from this crowd? 6V92TAA Engines.

Doug
Beach Girl
1986 Hatteras 53MY

[saltshaker]

The battery on the hard start side may be a little weaker or loose battery connection. I once had an issue where ground wire wasn't as tight as it should be so that side cranked a little slower.
Try this first. Given that it clears so quickly you may just have a weak battery or connection. Try starting the good engine first then use the parallel switch to fire the hard starting engine. If she spins fast and starts right up then you know its a voltage issue. If she spins fast but doesn't start then you need to dig deeper but that sounds like a low compression issue.

[Dan Mapes]

We had an issue like this with our stbd engine. It definitely cranked slower. A new battery charger keeping the 8D at float on both engines the same has resolved this. They both crank at the same speed based on sound, and they both fire up similarly now. Interestingly enough the slower spinning engine had the better compression numbers.

[SKYCHENEY]

I have a similar problem with my port 6V92. Hard to start and smokes when cold. In addition, it gets hot at WOT after 5 min. Both engines pull well and have same RPMs at WOT. Water coming from the port engine has twice the rise as Stbd. 70->90 vs 70->80. Diesel mechanic friend suspects dirty injectors. Any thoughts from this crowd? 6V92TAA Engines.

Doug
Beach Girl
1986 Hatteras 53MY

Sounds like low raw water flow. When were impellers changed last? Is there wear in the pump(ends, cam)? Is strainer clean?

Could also be a fouled heat exchanger or clogged shower head limiting flow.

[SEVEN]

Not sure if this will help but. I have a mechanic that has worked on DD's for almost 40 years and I am in aw of his knowledge so I'll pass on his little tip. He says to hold down the shut off button while you crank over the motors. Do that for 3 seconds then let the shut off button go and the motors will start. He says it will stop smokey starts. Again I'm not sure if that will work for you but it's a cheap way to check. Good luck.

[Dan Mapes]

In colder or cooler climates this gets some heat into the cylinders and aids starting.

[saltshaker]

It got down to the upper 20's here last Saturday night. Boat didn't want to start Sunday AM and the battery charger was turned off in error. Starboard engine was turning slow as was the port. Got the port to fire and used the parallel switch to fire the starboard. When they're cold they need all the juice you've got. If you can't spin them fast enough they just won't start.

[Finalee]

Another consideration is that there might not be anything wrong. Getting both engines in a twin engine boat to behave the same is an impossible task. There will always be a difference. Seeing how the actual performance is good, my thought is go boating!

[Victor_Chat]

Had this issue, replaced two injectors and tuned up the rack and no more white smoke

[holtcl]

The other thing that really helps on the cold starts is block heaters. In cooler weather I run mine over night, in the morning when I go to start up, the engine room is toasty warm, and the engines start immediately with no smoke. Using them also alleviated my concerns about excessive wear and tear due to cold starts.

Cheryl
Cinderella
1971 53 MY

[Reginald Buckingham III]

What he said.

[SKYCHENEY]

What he said.

Cheryl is a "he"??

[johnjen50]

Not even in P town! (on Cape Cod or Ma Bay)