Safe RPM range for 165HP inline six?

[Fordiesel69]

People rant and rave about the durability of the 165HP six. People run the 4cyl version very hard and near WOT and they just take it. Will the six take the abuse as well?

 

[mkast]

Re: Safe RPM range for 165HP inline six?

Will the six take the abuse as well?

By abuse, do you mean a lack of maintenance?

 

[Bt Doctur]

Re: Safe RPM range for 165HP inline six?

4500 is about the max if your propped correctly, lots of torque in those`s 6`s

 

[kilowatts]

Re: Safe RPM range for 165HP inline six?

Hi Guys:

According to my Mercruiser manual the WOT for a MCM 165 is 3900 - 4300 RPM. Of course if your boat is over or under propped then the figures change. Same if the boat is saturated or badly matched etc. etc. Generally speaking with good maintenance a 165 will give excellent service. I have 2 engines which are both over 35 years old and they run like new! I'm a big fan of the inline 6.

kilowatts

 

[Fordiesel69]

Re: Safe RPM range for 165HP inline six?

By abuse, do you mean a lack of maintenance?

No, what I mean is people run the 4cyl's wide open when tubing, cruising, etc because they are so slow and sluggish. They do seem to take this well without sticking the rods thru the side. If you do this to a V8/V6 it will not be long before it blows. I meant is the L6 as durable as the 120/140 when you are running it at high throttle / RPM?

 

[HT32BSX115]

Re: Safe RPM range for 165HP inline six?

If you do this to a V8/V6 it will not be long before it blows.

I run my V-8 at WOT fairly frequently, it hasn't blown up yet......

My last boat was a 1966 Marktwain (230 cu-in 6, 150 Mercruiser) that Dad bought new........we ran that thing at WOT many times in the 39 years that we had it......it didn't blow up either......

 

[Alumarine]

Re: Safe RPM range for 165HP inline six?

Slow and sluggish?????

I think all the configurations can be run at WOT safely.

 

[CheapboatKev]

Re: Safe RPM range for 165HP inline six?

The simple fact is that you are basing your question on automobile experience, where you can't run pedal to the metal and redline the motor without damage.

All true marine I/O's are built with a cam made for this type of WOT running.
Most failures at WOT are related to poor maintenance of other components such as water pumps, never changing outdrive fluids and such.
If all the components are in order, running within the WOT specs is fine.

Just saying....

 

[CheapboatKev]

Re: Safe RPM range for 165HP inline six?

Just saw your sig...
blown upper & lower OD huh?

 

[Fordiesel69]

Re: Safe RPM range for 165HP inline six?

Just saw your sig...
blown upper & lower OD huh?

Yep, the previous owner had shift cable WAYYYY out of adjustment, and then ran the drive low on fluid. This is how I picked it up so cheap. Engine seems absolutly perfect.

 

[Joshua Nichols]

Re: Safe RPM range for 165HP inline six?

1988 Four Winns Sundowner 235, 5.7-4V 260HP OMC Cobra.
1977 Glastron V-184 Crestflite, 165HP Inline Six Mercruiser, blown upper / lower drive!!!!!
1979 Sea Ray SRV-260, Twin 470's, Purchased at car auction by accident, was forced to take! Hope it is good!

The man loves his abuse....

Had a buddy that had a ol inline 6 in his ol boat.. We cut our teeth on it.. Was a pretty good set up..

 

[cr2k]

Re: Safe RPM range for 165HP inline six?

If the boat is properly propped it will run in the suggested range at WOT. Not like a car that can over rev going down a hill.

 

[jopes]

Re: Safe RPM range for 165HP inline six?

my dad had a 1968 glastron with the 165 in it. no hour meter, but he ran it at 2 speeds, idling for trolling, and wide open nearly the rest of the time. easily burned 400-500 gallons of fuel each summer in it. After about 25 years of running it, he decided to rebuild the motor. I think they were great engines to have in a boat.

 

[EZDuzIt]

I have a 17' tri hull with the Merc 165 straight six. With a 15"x 17 pitch prop I'm nuts on 4500 rpm and 40 mph at WOT. I could go with a 19 pitch, get a little more speed and lower the WOT rpm but for my application the 17 is perfect. It launches outta the water. If I go to a 19 pitch I'll lose that killer hole shot. My marine mechanic and my prop guy both say that engine can take 4500 rpm all day long and also says the manual is rather conservative. Mechanic says you can squeeze up to 4700 rpm but you're starting to play with fire at WOT for any sort of long run. But for the extra gtf off the water boost it'll handle it.