Help me identify a couple of things...

[JKG8R]

Greetings fellow Checkmate owners. I just made my first post in the 'welcome' section to show off my new 'new' 1990 Convincor 251. I've taken it out a couple of times and it is awesome and everything I hoped. I have two things I need to get some information on...

The boat has a bypass cooling system with only a crank driven water pump. When I tested the boat with a Merc mechanic he recommended I add a thermostat to the bypass cooling system so I bought a Hardin Marine bypass with thermostat kit (with a 140 degree thermostat). This weekend the water temp again never moved off the minimum so I need to troubleshoot the gauge but my concern is the oil temp. When we were riding ~3,500 -4,000 RPM the oil temp got up to ~250 degrees so I backed off and the temp came right back down. This morning I started looking and I don't think it has an oil cooler. It has a remote oil filter and bracket but I don't see anything with a water jacket anywhere. Shouldn't it have one? It's a 450HP 518ci engine so I would think it needs one. This is the oil filter and hoses:



My other question is: What the heck is this?!? It's an aluminum canister mounted on the starboard side of the engine. The tank has no markings on it, it has a pressure valve and a solenoid valve looking thing at the base and then is plumbed around to the port side of the block in the front just above the oil pan. It's a GEN VI block if it matters to anyone. I haven't cut the wiring harness apart yet but it appears the solenoid / relay gets ignition power.




Thanks for any input / advise / assistance. : )

 

[Gimme Fuel]

YES you need an oil cooler! You should have at least a 2" x 18" cooler for that HP. It should be plumbed in the oil lines after the filter unit in the return line back to the block adapter. That cannister looks like an oil accumulator/pre-luber. That solenoid valve should be wired to a switch or the ignition to release just beore starting the engine to prevent dry starts. As ar as the bypas system, those will cause the engine to run very cool. The block temperature doesnt matter much. Your oil temps are what to watch. You should be around 170-180* cruising and under 230* for hard runs. At least that is what I shoot for. Oil temps above 250* start to break down dino oils and really thin causing decreased film strength. The only problem a cold block would have is if you run efi and have not disabled the cold enrichment mode.

 

[Gimme Fuel]

Also, because of the cooler running block, your oil cooler should either have a built in oil thermostat bypass or you can plumb in an external oil thermostat that will allow the oil to bypass the cooler and get up to temp. The oil needs to keep warm enough to evaporate moisture and condensation out. Also, i the oil is too cold it wont flow properly putting stress on your whole oil system, not iltering as easily, and causing the pressure bypass valvesin the block and the filter to open.

 

[JKG8R]

That is exactly what I needed to know. Thanks for taking the time to answer. For the oil cooler on the water side, will I just come off the water pump with full-size hose (1-1/4"), go through the cooler and then back into the crossover pipe on the block? Are there any brands in paticular you would recommend or stay away from?

 

[Gimme Fuel]

yes, the cooler will plumb inbetween the output of your sea pump and the inlet of your crossover pipe (piece replacing block water pump). They are availible with the 1-1\4" slip on ends. You should also be running a small cooler for your power steering fluid also. That little pump can make a lot of heat in that system if you cruise at sustained high RPM's. CP Performance has many to choose from at decent prices and they are good quality. The integrated thermostat coolers are very expensive though. I went with a 3x"18" standard cooler on mine with a Derale Perormance 1/2" NPT oil thermostat from Jegs for $53. Very nice piece for the price BTW.

 

[JKG8R]

Gimme Fuel, I really appreciate your help on this. I drew up a quick cooling system schematic to show how I understand it should be done. Am I missing anything? I'm going to plumb it so I can add a power steering cooler between the engine oil cooler and engine down the road. The engine has ~100 hours on it since it was built and the PS fluid looks and smells fine (not burnt or black). I'm going to keep an eye on it but I don't plan on any extended high RPM runs

 

[Gimme Fuel]

Very nice drawing! You got it right! The only thing you might need to do is drill a 3/16 hole or two in the thermostat to allow a little extra water to get through to keep your exhaust water jackets full and reasonably cool until your engine reaches temperature. A lot of guys end up just running a restrictor instead of a thermostat. Also, with the lack of a circulating pump, there is the possibility of steam pockets to form in the back of the heads. Having a crossover between the two rear cooling ports on the head and T-ing them into a small overboard dump line eliminates this. Crossovers can be a PITA to get setup correctly but it is one less thing to fail and makes the motor look nice.

 

[JKG8R]

It's a shame you're 1,000 miles north. It's supposed to be 75 and sunny this weekend so we could take her out on the river and let you check it out for me.

 

[ezstriper]

eddie marine has a nice oil cooler that I run, I do not run the oil thermostat, not needed in my opinion...others my disagree, you will need the P/S cooler now as will foam up the fluid without one pretty quick after running for any length of time...plumb with #10 line and watch out for 90 deg fittings etc...

 

[Gimme Fuel]

It's a shame you're 1,000 miles north. It's supposed to be 75 and sunny this weekend so we could take her out on the river and let you check it out for me.

Haha....I wish I was closer also! I'm tired of snow already and it isn't even officially winter yet

Also, now that I look at your pics on the computer instead of my not-so-smart phone, I see your oil lines look like they are made of hydraulic lines and fittings. You should maybe replumb these with NPT nipples and pressure hose or go with the AN style fittings. Hydraulic fittings have mush smaller orifices than comparable sized AN fittings because they are designed for much higher pressures. With 1/2" hydraulic fittings, you aren't gaining much over the stock 3/8" oil lines. I went with all 1/2" NPT fittings with 5/8" nipples and lines for my oil system. Quite possibly overkill, but the easier oil can move through the system, the cooler and less aerated it stays. I also am using a tandem parallel oil filter unit so I can use standard filters. The hp filters/racing models have much larger filter pores so they can flow high volumes. This consequently will let fine debris/dirt go through the engine. Not an issue for racing engines that are frequently rebuilt but could possibly cause damage on engines that we build and use for years on end. Just something to think about. I try to find the longest/highest capacity filters that will thread onto my filter unit.

 

[JKG8R]

I agree with the hoses. I'm going to use -10AN hoses and fittings and ditch the 90 degree turns. I'm trying to figure the best way to position everything and it would be a LOT easier to install the cooler between the drive and raw water pump. Does the Bravo 1 have a water pump to help push or does the raw water pump have to draw the water up and "prime" itself? I think the cooler is going to go on the floor adjacent to the engine so there will be a lot of 1-1/4" hose wrapping around to feed the pump, turn and go back into the cooler then turn 180 and go back to the crossover pipe connection. Thoughts?

Also, ezstriper, you said you don't run a thermostat. Any reason for that? Do you have any problem with the oil getting up to and staying at temperature?

 

[Gimme Fuel]

No, the only water pump on a Bravo is the belt driven vac pump. You don't want to put your cooler between the drive and pump. On most installations, the water hose runs from the pump to the rear of the motor, up and over the bell housing (usually where power steering cooler is) then back down along the other side of the block (usually where oil cooler goes) then up the front into the crossover inlet (you can flip your crossover to put the inlet on the other side if need be). It is a lot of hose but it looks clean when installed. That is how Merc does it too. I mount my coolers and everything else to the block so it is a complete drop in ready to run unit.

 

[JKG8R]

That makes sense. I hate to ask but do you think you could post or send me a picture of how your coolers are mounted and your hoses are routed? If I could mount the cooler over the bellhousing that would definitly make it a cleaner installation but I don't know if I can do that until I have one in hand and see what kind of brackets I would need to make. Thanks for all the help.

 

[Gimme Fuel]

eesh, I don't have pictures yet of my setup. It is all a pile of parts and the old method I had was pretty much stock Merc coolers and brackets. I have yet to make the ones for my new coolers.

Fairly stock from Merc:

Heavily Modified:



Sorry, I don't really have any good pics of exactly what you are looking for.

 

[JKG8R]

If you don't have them availble don't sweat it. I'll order up a cooler next week after Christmas, so my wife doesn't shoot me, and spend a couple of evenings staring at it until I find what looks the best to me. Not too many warm days left so I'm anxious to go back out before cold weather sets in for 2 months.

 

[Wrenchmate]

Since I also own a 251 Ive been paying attention to this thread.
I know Gimme fuels knowledge of these engines is impeccable but
I cant believe why someone would leave this off.
Im probably wrong, I thought all big block convincors came with factory coolers installed.
My water hose runs under neath the engine to the cooler and since I have
headers its fairly to spot but with bigger factory or other manifolds it can
blend in, tucked under there neatly. (Tight engine compartment)
Sorry to butt in, just thinkin it might still be in there some where.
Gimmefuels engine rocks.

 

[Gimme Fuel]

Im guessing whoever built his motor knew their way around a big block but didnt know the demands of marine engines. JKG seems to understand this quite well based on his nice technical drawing he made. If one was there, im sure he would have found it by now. I give him the beneit of a doubt on this one. I have seen this happen when car guys try to build a boat. Plus his lack of 1-1/4" water hose suggests there isnt a cooler either. Regardless, his oil temps are high and it needs cooling system attention.

 

[Gimme Fuel]

Thanks or the compliments by the way! I just wish that one ran as good as it looks! simple rookie mistake cost me big time! Had to basically start over. On the flipside, it is going to be about the strongest a pump gas naturally aspirated 540 can be. Now back to JKG's issue after that commercial.break......

 

[JKG8R]

Good morning guys. Definitly no coolers installed on my engine. It is a Gen VI engine with a remote filter adapter on the block and a remote HP-4 filter. Like you said about your engine, the people that built the engine did a fanstastic job and used all the right parts but I don't think they understood the heavy load it was going to run under. When I test drove the boat, running ~45mph it is on the primaries cruising along and the oil temp stayed ~200 degrees and cooled right off when you backed off. The oil pressure hot is still close to 15psi @ idle and over 50psi @ 4,000 RPM When I installed the Hardin-Marine crossover setup with a thermostat to get the block temp to come up, the oil temp went up as well. Cruising at the same speed the oil temps are well over 200 and when I push it up to 4,500 RPM for just a couple of seconds the temps went right up to 240 and very slowly came down when I backed off.

I'll look at the receipts when I get home and update what I'm missing but basically from memory my engine is a Gen VI 454 block, 0.030 over with a forged 4.5" crank (518ci), forged rods and pistons (balanced assembly), Comp Cams Xtreme Marine hyd. roller cam (284/290 advertised), 502 heads with a 3-angle valve job and upgraded valves, aluminum intake with a Holley Marine 750 carb, K&N arrestor and MSD ignition. After sitting for months the compression was still dead on across the board and leak-down was even at ~10%.The Merc mechanic that I paid to look at the boat with me said it has IMCO headers but I can't see any markings on them so I have no idea what they are. It also has 4" through-hull exhaust. I still haven't run it WOT to see what it will do but the engine looks like it will be happy with 5,000RPM+ even though I don't plan on doing that very often. It ran just over 60 on GPS @ 4,500 RPM (with the family loaded up) so I expect I can get it over 70 one of these days. Oh, I have a Mirage 25P 3-blade prop if that matters to anyone reading this.

Just a side note: I installed a Garmin Chartplotter with a GFS10 fuel flow sensor when I bought the boat and the last time out it was getting 3.2MPG at 35MPH with my wife, 3 daughters and 50 gallons of gas in the tank. I thought that was fantastic. When I slowed to 25MPH my mileage went down to 2.5MPG. The couple of times I pushed it up to get into the secondaries I wasn't looking at the display to see how bad it got but it sure sounded sweet.

 

[JKG8R]

Well it's been a while but I'm back on my project. We took the boat out a couple of times in the past month and it's been running great. Even without a cooler the oil temps were running right at 240 degrees if I keep the speed at ~30MPH. We made a 60 mile trip two weekends ago without issue which really boosted my confidence in the boat. After a lot of reading and debating in my head I opted for a Hardin Marine cooler (2" x 16" overall length) with no thermostat. A local guy with a GTX 251 and a Magnum engine said he doesn't use a thermostat with a cooler that size and it works great. If I end up switching this out for a 3" cooler I'll add the thermostat to be safe. I have a few pics of what I did yesterday afternoon:

First, I removed the hydraulic hose and fittings that were connecting the remote filter. I went back with -10AN hose and no 90 degree fittings.


I am using a mixture of 1-1/4 stainless steel tubing and marine hose for the water lines. I need to tuck the cooler and lines up to the engine more and get it all strapped down but this is basically it:


You can see the hose with the green stripe, that is the hose from the Bravo pickup. Once day when the engine is pulled out I will mount the cooler in the bilge or somewhere to make it cleaner but for now this is the best I could come up with:


I also ditched the thermostat and I'm going to play with a couple of restrictor plates to get the water temp dialed in to ~140 degrees. I was using a thermostat from CP Performance with the steam ports but it still seemed like the temp danced around more than I wanted it to. It's supposed to be in the 70's this weekend so I'll take it out and see how it does. If the oil temps are good I'll push it a little bit and see what she can do. : )