CAT Motors

[alldodge]

Only know of a few on forums that may have the knowledge to answer to questions, but sure like all thoughts just for discussions. We have been seeing water pressure issues even prior to the CAT motors, and now I'm seeing things getting even worst.

Have seen a few threads talking about issues with boats and water pressure. Comments for Merc lead back to the poppet valves (such as on 4.5's) but I'm wondering is it just poor design. Similar issues are showing up on OSO with larger motors.

Is water psi that critical for these motors, and if so what are the pressure parameters?
What happens if a motor cruises from cold to warm water and pressure changes?
Would it help to install a larger pump to move more water and increase pressure?

If things like this cannot be determined why should (not would) anyone buy a boat with a CAT motor

Would really like to understand the issues and if I'm just going off in the wrong direction and missing the point(s)

 

[Bt Doctur]

To me the water pressure is a useless item. With proper service intervals and keeping a close eye on the "running temperature" you should remain trouble free. I dont think the CAT motors runs that much hotter .Never seen the specs on it. GEN II or Bravo the pumps are the same. Maybe the issue is with poppet valve design instead of the thermostat design.Trying to get to work on one to determine the resistance values of a motor not throwing a pressure code and create a resistor package to eliminate it.

 

[alldodge]

Do agree with you BT, I see of no reason for the water pressure sensor tied into the ECM/PCM. It will catch some issues before they get worst, but how and when. Older motors it's just been a pain in the back side trying to determine what is happening, when the motor has no other issues

 

[alldodge]

Add muc Fun Times kenny nunez see if Ya'll have any insight

 

[Scott Danforth]

not sure what value the water sensor truly has. the sensor is not water friendly with most failing. it is a standard COTS pressure switch designed for anything but salt water/brackish water. a simple pressure gauge (standard on many outboard boats) provides 99% more information

I agree the spaghetti farm that is the merc 4.5 cooling is way too complicated.

catalyzed exhaust generates a bit more heat on the exhaust side, so the CAT motors cooled with a full system HX wold need a bigger HX. half system would be fine

I personally believe that all I/O's should be a half-system with a full system being an option. the problem is the HX adds about $750 to the cost of manufacturing ($650 for the cooler, $100 for brackets, etc.), after subtracting the spaghetti which is the Merc cooling hose bundle, about $500 total cost upgrade

the average consumer just shops on price. which is why every penny is looked at.

however I personally would shell out the extra $1000-$2000 on a new boat purchase if the standard was HX cooling. then again, i turn wrenches as a hobby, assist in service work, and fully understand the ounce of prevention is better than a ton of cure.

going to half-system HX cooling, the whole system becomes simple with an engine driven pump. (would have to abandon the outboard originated pump in an alpha leg)

incoming raw water hits the PS cooler, then the combo fuel/oil cooler..... goes thru the raw water pump to the HX, then out the exhaust. that is a rubber hose from the PS cooler to the combo cooler (or combo PS/Oil and fuel cooler), a rubber hose to the raw water pump, a rubber hose from the raw water pump, three hoses between the long block and the HX (lower, upper and fill), and two exit hoses to the manifolds. there would need to be 3 small bleed hoses to self bleed the system. the expansion tank would need to be a separate tank/separator, similar to the MOAS system from Volvo Penta (MOAS stands for Mother Of All Separators)

a full system would require the exhaust manifolds to be plumbed in off the back of the head in the intake manifold, and then exit to the circulating pump inlet with restrictors in the manifold feeding the T-stat.. two extra hoses, however a very simple system without check valves.

it however would take a hit upside the heads to get Merc to see the simplicity in that (its similar to PCM and VP offerings)

 

[GA_Boater]

Mercs plumbing nightmare is made even more complicated with their blockbuster innovation - Single Point Drain for winterizing. I see the air assisted SPD has a lot of complaints around the InterWeb, too. A bicycle tire pump to pressurize the system - Really?

Aren't all new Mercruisers CAT equipped or only required for some parts of the country?

 

[alldodge]

All new motors under 500 HP are required to have CAT, so not just Merc (VP, Indmar, etc)

Don't see me ever buying a new boat for this reason

 

[Scott Danforth]

EPA rules came out in 2010. some manufacturers could use credits for a while to phase in, however i believe most of the credits are used up.

agreed, dont see me buying a new boat unless maybe diesel.

 

[Lou C]

If I were buying new the CAT engines were the end of inboards for me. Everything added, made the one advantage I/Os had (simpler less expensive automotive based engine vs outboards) disappear. If I'd have to take an EFI cat engine with all the extra added complexity I'd at that point prefer an outboard to get away from all the other I/O maintenance. The only remaining advantage is the ability to have closed cooling. Nothing else. So in the future it will be all outboards for me.