A couple of questions re: 1986 mercruiser 454 7.4 L 340 h.p. engines

[heatz1express]

O.K., so first let me say I have always had good luck getting answers on the iboats forums - a good bunch of boaters!

Today, my questions have to do with the engines and drives in my new to me boat. 1986 ChrisCraft Commander 336 with twin 454's and borg/warner transmissions.

first question; Having recently replaced the thermostats in both engines, I noticed that on the Starboard engine there is a third smaller diameter hose coming/going from the housing. It is only maybe 5 or 6 inches long and goes straight back. WHAT IS IT FOR ? and why isn't there one on the port side. Also, when I bought new thermostats the parts guy said that the right thermostats for the year of my engines was 140 degrees. That is what I put in both engines (unless the wrong thermostat was in the package) and the starboard engine still runs around 160 degrees as opposed to the port engine which is running right around 140. What is the correct operating temp. for these motors and why the difference in temps.?

second (and last for now) question; On the portside (which had a new shaftlog installed recently), a moment after I have finished shifting, either from forward or reverse, to neutral there is a squeaking almost high pitched whistle noise that lasts a short time and then stops. A local marine mechanic I spoke with suggested that it is probably the shaft rubbing on the shaftlog packing as it slows to a stop and that it will go away over time. His suggestion makes sense to me since it is a new shaftlog, but the "squeak" seems to be lasting longer after I shift out of gear. Anybody know what it is? Should I be checking my trans. fluid level?
Not making sense to me, since the noise occurs not while shifting, but immediately after I shift to neutral. How can that be trans. ?

 

[Bondo]

Re: A couple of questions re: 1986 mercruiser 454 7.4 L 340 h.p. engines

O.K., so first let me say I have always had good luck getting answers on the iboats forums - a good bunch of boaters!

Today, my questions have to do with the engines and drives in my new to me boat. 1986 ChrisCraft Commander 336 with twin 454's and borg/warner transmissions.

first question; Having recently replaced the thermostats in both engines, I noticed that on the Starboard engine there is a third smaller diameter hose coming/going from the housing. It is only maybe 5 or 6 inches long and goes straight back. WHAT IS IT FOR ? and why isn't there one on the port side. Also, when I bought new thermostats the parts guy said that the right thermostats for the year of my engines was 140 degrees. That is what I put in both engines (unless the wrong thermostat was in the package) and the starboard engine still runs around 160 degrees as opposed to the port engine which is running right around 140. What is the correct operating temp. for these motors and why the difference in temps.?

second (and last for now) question; On the portside (which had a new shaftlog installed recently), a moment after I have finished shifting, either from forward or reverse, to neutral there is a squeaking almost high pitched whistle noise that lasts a short time and then stops. A local marine mechanic I spoke with suggested that it is probably the shaft rubbing on the shaftlog packing as it slows to a stop and that it will go away over time. His suggestion makes sense to me since it is a new shaftlog, but the "squeak" seems to be lasting longer after I shift out of gear. Anybody know what it is? Should I be checking my trans. fluid level?
Not making sense to me, since the noise occurs not while shifting, but immediately after I shift to neutral. How can that be trans. ?

Ayuh,.... How 'bout a picture of the mysterious water line, 'n where does it Go too,..??

Have ya changed the raw water pump Impellers,..?? That's Always the 1st place to look with Heat issues,...

I'm guessin' yer boatin' in freshwater, I'd run the 160? t-stats for abit better fuel burn,...
The 140? stats are for keepin' salt outa the castin's,...

'n, as for checkin' the tranny oil levels,.... I guess, Ya,....
Bein' a Mechanic/ equipment operator/ boater,...
I check All the fluid levels, Every day at 1st start up,...

 

[alldodge]

Re: A couple of questions re: 1986 mercruiser 454 7.4 L 340 h.p. engines

Not knowing your serial numbers and not being able to see what your looking at I'll add the following: There were two different thermostat(TS) housing made during 1981 and 1987 for the 340hp inboards. Both used 140 degree TS but plumbing was different. I'll at least one of your engines has had work done on it. It could be the older engine (mybe starboard) may have more build up on internals, but 160 isn't bad.

The shaftlogs you have should leak a bit of water. The water leak is what lbricates the seal. No expert hear, but what I have read and been around, the seal should drip with the engine not running once every 12-15 minutes. With the engine running it should drip once every 30 seconds. SO far as checking the trans fluid tells me you haven't and therefore I would say yes, it needs checking.

Edit: Was to slow posting, Bond-o is the expert

 

[heatz1express]

Re: A couple of questions re: 1986 mercruiser 454 7.4 L 340 h.p. engines

Ayuh,.... How 'bout a picture of the mysterious water line, 'n where does it Go too,..??

Have ya changed the raw water pump Impellers,..?? That's Always the 1st place to look with Heat issues,...

I'm guessin' yer boatin' in freshwater, I'd run the 160? t-stats for abit better fuel burn,...
The 140? stats are for keepin' salt outa the castin's,...

'n, as for checkin' the tranny oil levels,.... I guess, Ya,....
Bein' a Mechanic/ equipment operator/ boater,...
I check All the fluid levels, Every day at 1st start up,...

Thanks Bond-O ! when you are right you are right... and you are right. I'm just hoping someone on iboats can tell me, "It is your shaft log packing! mine did the same thing and it is normal until the shaft wears into the packing". "The noise you are hearing is nothing to worry about" !

The only thing I can think of, with regards to the third hose from the thermostat housing, is that it might be for hot water - providing hot water to the water system.

 

[Bondo]

Re: A couple of questions re: 1986 mercruiser 454 7.4 L 340 h.p. engines

The only thing I can think of, with regards to the third hose from the thermostat housing, is that it might be for hot water - providing hot water to the water system.

Ayuh,... possibly, But,...
Normally the hottest water is under the t-stat, not over it,...
Generally,..
Hot water heaters tap outa the intake manifold, before the t-stat, 'n dump back into the circulatin' water pump housin',...