Cat 3208TAs slow to heat up

[jaredjensen]

We recently bought a 1994 Riviera 42 with low-hour (500) twin Cat 375HP 3208TAs. The engines start quick and run great, but both take a long time to warm up, at least according to the gauges. We leave the slip a couple minutes after starting the engines, and then run under light load (600-800 rpm) until the gauges indicate operating temp, which takes almost 30 minutes. What's even more odd is that the temp gauges don't read anything until the engines are warm, at which point they rise from the minimum (100F) to ~170F in 2-3 seconds.

It seems like a stuck thermostat, but I've heard the Cats have a dual thermostat system that basically never fails, so to have two engines with this issue seems like a stretch.

I need to have my wife drive the boat during warmup while I check engine temps with an IR gun every few minutes to try to narrow it down to sender, gauge or thermostat. But I figured I'd ask here to see what's normal for these engines and for any other troubleshooting tips. Thanks!

 

[Mac2]

I’m not a professional mechanic. I have 3208Ns. They hold 14 gallons of coolant each. Think about heating that much fluid on the stove. It will take a long time. I can only go 7 knots max in the canal where I live. I don’t think I ever get to 180 degrees until I get to the lake, 45 minutes away, and Im able to speed up. Im guessing the sudden temp increase is the result of the thermostats opening up at a specified temperature.

 

[jaredjensen]

It takes us 15 minutes to get out of the harbor at no-wake speed, so the slow warmup isn't a huge deal. It's just about 10 minutes longer than the TAMD61As in our last boat, where I'd roughly stick to the "10 RPM per degree" rule, e.g. 1000 RPM at 100F, so it warmed up faster. Since I can't see the Cat temps until they're warm, I'm doing a conservative and completely non-scientific time-based approach of 1000 RPM after 15-20 minutes.

If the sudden gauge increase is due to thermostats opening, then I think that means the sender is located somewhere that doesn't see actual temp initially. Which seems weird, but does jive with the somewhat cryptic note in the manual about "don't load the engine until the gauges move". One of my buddies has the same engines, but his warm up faster and gauges read something during warmup, so I figured I had a "problem".

 

[Mac2]

Mine do increase slowly, so it is strange how your gauges are reading, but I wouldn’t worry to much-as you said, hard to believe both engines have the same issue.

 

[Lepke]

With a dual thermostat engine, if one sticks partly open, it takes a long time to warm up.
An engine doesn't normally go from 100° to 170° in seconds. I suspect a sticking thermostat or failing sensor. Most larger diesels have a small bypass around the thermostats so there is always some coolant flow. Even my Perkins 4108 generator engine has one.

 

[Jeff F]

Maybe a related question, but do those engines have raw water engine oil coolers?

I ask because I recently was chatting with the owner of a DE boat with a 3208TA, and his big complaint was that the engine wouldn't maintain proper operating temperatures at slower speeds. I've been wondering since about that.

 

[jaredjensen]

With a dual thermostat engine, if one sticks partly open, it takes a long time to warm up.
An engine doesn't normally go from 100° to 170° in seconds. I suspect a sticking thermostat or failing sensor.

With the low hours, I was thinking the thermostats could be sticky from just not being exercised much, but I don't know the usage or service history. I've also heard they're kind of a pain to change, but haven't really looked into it yet and was considering just replacing a sender on one engine to see what happens first. My project list is still pretty long (it never ends), so it might be a while before I get around to actually doing anything about this.

 

[jaredjensen]

Maybe a related question, but do those engines have raw water engine oil coolers?

I'm pretty sure they're fresh water cooled. And I haven't noticed the temp dropping after throttling back to idle, but I'm usually busy getting the boat ready to put away at that time. I'll pay attention next time.

 

[Tired Trawler]

Greetings,
Another possible factor in slow warm up could be a domestic hot water tank & or hot water cabin / bus heaters in the engines fresh water ( coolant ) circuits, Quite common in our neck of the woods on the westcoast.
Hope this helps.

 

[O C Diver]

Do you have service records?

I have a debilitating disease called CDO (Obsessive Compulsive Disorder but in alphabetical order as it should be). Without service records, I would want to flush the coolant passages, atleast rod the heat exchangers, replace the thermostats, replace coolant, and replace radiator caps. The boat is 31 years old and barring service records is possibly original cooling equipment. It would be a real shame to spend thousand$$$ doing head gaskets versus hundreds servicing the coolant system.

Ted

 

[jaredjensen]

Another possible factor in slow warm up could be a domestic hot water tank & or hot water cabin / bus heaters in the engines fresh water ( coolant ) circuits

The port engine has a coolant loop for the water tank and a cabin heat exchanger, and it does take 3 minutes longer to come up to temp than starboard. I actually ordered a diesel hydronic heater this morning and will be using that for water and cabin heat instead of the engine.

 

[jaredjensen]

The boat is 31 years old and barring service records is possibly original cooling equipment. It would be a real shame to spend thousand$$$ doing head gaskets versus hundreds servicing the coolant system.

There are no records, but the previous listing indicates the "complete cooling system" was serviced 4-5 years ago. It's on my list to change the coolant and at least check the heat exchangers for buildup (in addition to all other regular maintenance to establish a baseline), but right now I have no indication of overheating, even at WOT.

 

[Insequent]

You may be constrained by slow speed zones, but I would think you should run at a little more rpm if possible. Say 1000. That will still be light load, but remember that load = temp increase.

 

[jaredjensen]

I would think you should run at a little more rpm if possible. Say 1000.

That's pretty much what I've started doing. It takes about 15 minutes to get out of the no-wake harbor, and I figure by then the engines are warm enough to bump the RPM to 1000 or so to get them up to temp faster. It'd be more comforting to see something on the gauges before then, so I'll probably eventually try to resolve that.

 

[tiltrider1]

The Cat 3208 will take for ever to warm up at 800 rpms. They just are not generating any heat. I run 800 rpms to get out of the marina then I bump them up to 1200rpms. Still it takes 5 to 10 minutes to see any heat. Once I see some heat I bump up to 1500. After they warm up to 195 degrees I take them up to 1750 rpms.

At 800 rpms it would take me more than 30 minutes to get to operating temperature.

 

[Portage_Bay]

It's a 3208. Compared to many engines in recreational boats more iron and more coolant. It's not going to warm up until you work it a bit. The sudden jump from minimum to 170 in 2 - 3 seconds points to a sender or gauge problem in my opinion. You're going to check with an IR gun to observe the "warm up". Do that before you fall too far down the rabbit hole of dead end trouble shooting.

 

[heysteve]

On my 3208N, the service manual says to replace the "temperature regulators" every two years or 1000 hours.

 

[Mac2]

On my 3208N, the service manual says to replace the "temperature regulators" every two years or 1000 hours.

Good information. Thanks

 

[Lepke]

With twins, any questionable sensor, swap between engines. If the problem moves, it's the sensor.

 

[stevemitchell]

check with an IR gun to observe the "warm up"

The best advice so far is above from @Portage_Bay - checking the engines with an IR gun while warming up is not only great advice, it's one of the first things I always do on a new boat, or a boat I'm troubleshooting. I do not trust analog gauges, especially older ones, until I know that they're reading from the right place and are accurate. Plus, to your point in one of your earlier notes, where is this particular gauge reading from - is the engine hotter elsewhere? Colder?

Having had 2 boats with 3208 variants, I agree with everyone else about them being slow to warm up without any decent load on them. However, I don't think I've ever seen them go from low temp to operating temperature in a few seconds. Definitely worth hanging out with an IR gun in the engine room during that time to see what happens.

Congrats on the new boat

 

[Portage_Bay]

The best advice so far is above from @Portage_Bay - checking the engines with an IR gun while warming up is not only great advice

I have to credit OP with suggesting he use an IR gun

I need to have my wife drive the boat during warmup while I check engine temps with an IR gun every few minutes to try to narrow it down to sender, gauge or thermostat.

I've got older twin Cummins 6BT that show different temps and warm up times. Checking with the IR gun shows it's a problem with the old analog gauges and or senders.

 

[jaredjensen]

Hrm, I didn't get notifications of replies until today, so belated thanks for all the input! I haven't gotten around to troubleshooting this yet, but will post back with results when I do. I'm currently up against the clock to get a hydronic heating system installed before the temps drop much more, but that's another post!

Congrats on the new boat

Hey Steve! Hopefully we'll keep this one more than three years. =)

 

[stevemitchell]

I have to credit OP with suggesting he use an IR gun

Oops, sorry!

 

[Leeward III]

Cat recommendations are for the temp regulators to be changed every 2 years. They also recommend 190 degree regulators that are faster acting, eliminating some of the white smoke when cold.

 

[Deano]

I had a trawler with 3208 TAs and could tell when the thermostat’s opened by a drop in temperature. I guess it depends on sensor location.

 

[heysteve]

Cat recommendations are for the temp regulators to be changed every 2 years. They also recommend 190 degree regulators that are faster acting, eliminating some of the white smoke when cold.

I was wondering about that temp change. My boat came with two 165 regulators but when I purchased recently from Cat they were 190s.

 

[SteveK]

What? you have to wait for the coolant temp to reach operating temp before you go to cruising rpm. Long wait ahead.
The engines need a short warmup, oil circulated which is all done by the time I untie and leave the no wake zone. Coolant is still slowly rising as the engine block is absorbing the heat until it starts passing it on the coolant.
Forgetaboutit. Just worry if the temp goes above thermostat open temp.

 

[Leeward III]

If you really want to get into the weeds with your 3208, try CAT SIS2Go app, which is serial number specific , costs $15 per month, has all you’ll ever need to know.

 

[Mac2]

If you really want to get into the weeds with your 3208, try CAT SIS2Go app, which is serial number specific , costs $15 per month, has all you’ll ever need to know.

I attempted to create an account, but was denied. Stated I needed to contact my dealer to get their permission?

 

[Leeward III]

Try the Cat Central app, which also wants your dealers name. As we cruise up and down the east coast we use dealers from Pennsylvania to Florida. When you buy parts open an account or give one a call, I’m sure they would be very accommodating.