6BTA 5.9 M3–Coolant System Maintenance

[Mike Uliasz]

Just purchased a 97 Pursuit with twin 6BTA 5.9-M3 engines, 370 hp. Going thru the cool systems and removed the heat exchangers to clean them. 1 engine has the blue coolant so that’s an easy match, but one has RED. By the color chart is looks more like the NOAT fleet guard, but not totally sure. Coolant was changed 5 years ago, so it sounds like i can just added more to top it off. Any tips or best guesses? Would there be an issue if OAT was mixed with NOAT?
Thanks
Mike

Topic

[Mike Uliasz]

Ran the boat for a 2nd time after the coolant system Maintenance. Had to get the bottom cleaned by a driver to get her to plane after sitting for 6 weeks. All good temp wise, starboard engine that ran hot (200-205) and had the after-cooler blockage cruised was right on 180 and the port ran the same as B4 just over 180 at cruise. Heat gun showed 177 at the hottest spot I could find (front coolant hose going into the heat exchanger). Water temp 77-80 degree. Ran the boat in the 2200-2400 rpm range.

2600 was the max for rpm’s, so that’s my next issue. The max rpm’s at idle; port 3000, starboard 3300. Buddy recommending getting the tach’s calibrated first at idle. Other thing is the boat had been sitting prior to purchase, so the fuel was old. I did put 100 gallons in each tank with Diesel Kleen cetane boost. Surveyor recommended it, said don’t mix with any other additives.

Port engine had a slight touch of dark exhaust smoke at cruise too, barley see it. Like to run the boat till the end of the year and burn out the old fuel, then clean the bottom/running gear good. probably needs to get the prop’s checks. Get the tach’s checked now. Any do and don’t recommendations?

Wooden marshmallow skewers worked great for cleaning the after-coolers and heat exchangers … lol

Thanks
Mike

[Mike Uliasz]

Finished putting the 2 after-coolers back together, much easier job and the starboard one back in the boat. QQ, the port after-cooler is heavier, the casing seems thicker and the core is heavier. Buddy mentioned it maybe a newer one? That the after-coolers were beefed up on later models. The engines are 96. Top 2 pics off the starboard, lighter one and the bottom pic off the port.
Thanks

[Mike Uliasz]

Thanks Mike! Cleaned all the parts up this weekend and will assemble tonight with Tony’s kit. Where did you install the flesh water flush? My buddy and I were discussing where to insert/place B4 the after-cooler to avoid running the engines. Have one on my Shamrock and it works great.

[Mike Pettee]

Fresh water flush setup is worth its weight in gold and then some. Quick and easy. I flush mine after each use as soon as it’s not deathly hot in the engine room.

[Mike Mason]

Blockage is from sea water sitting in the coolers. Get them up to Tony’s spec and then install fresh water flush systems. Worth their weight in gold.

Watch those temps steady to spec once all cleaned and reinstalled.

Keep up the good work.

[Mike Uliasz]

Heat Exchanger

The heat exchangers had some blockage from the zincs, guess that’s from them dissolving in the raw water from lack of use?

The after-cooler blockage, is that from the zincs? The other after-cooler core (no pic) was rust colored with only a few tubes blocked. Next steps clean and pressure test the cores then reassemble. Got the kit in the mail yesterday ?. Thanks again for the tips and input!

[Tony Athens]

Aftercooler Servicing

Glad you went for it……. I’d say 75% blockage on the seawater side..

Tony

[Mike Uliasz]

Aftercoolers apart

Made some surprising progress thanks to the recommendations and help on this forum and website. After-coolers off and apart. First one much easier, was greased and just needed one solid tap from a 3 lb sledge hammer with a block of wood. Second one took a little more work going back and forth. First 4 pics are off the starboard engine that ran slightly hot at cruise. Other 3 off the Port. Any input on the cores is appreciated. Thanks Mike

[Mike Uliasz]

Rob,
Thanks for the tips, same boat and motors too LOL. Good old sledge hammer and penetrating oil. The oil cooler can basically be cleaned in place with a wood rod with the aftercooler off and the hose on the other side disconnected.

Thanks again for the link, very helpful.

[Rob Schepis]

Mike Uliasz wrote:

Is there a special process to press it out or can I tap it out with a block of wood?

Some slide out with the push of two thumbs, others won’t budge with a block of wood and a sledge hammer. Only you know what you are dealing with. Use the search function, plenty posted on this forum and this site on dealing with core removal, aftercooler service, etc etc.. Here’s one forum topic regarding removal: https://www.sbmar.com/community/topic/6btas-aftercooler-service/

[Mike Uliasz]

After-cooler Maintenance

Pulled off one after-cooler this weekend, 2/3’s of the bottom tubes were covered with a thin coating of white crusted, cleaned them out with a wooden rod and barnacle buster. Now I need to remove the core. Is there a special process to press it out or can I tap it out with a block of wood? Probably best to bring it to a professional to remove and pressure test? Looking in the air intakes, it did not look like any water had gotten it. There was a coating of white grease around the cord, housing and cap on the inside.

[Mike Uliasz]

Thanks Rob!

[Rob Schepis]

Mike Uliasz wrote:

Look like kit #2 for the after coolers, any other gaskets needed B4 placing the order?

Yes on the o-rings, no on gaskets. Order the alco grease too unless you have something comparable already. https://www.sbmar.com/product/alco-metalube-boat-owner-size-with-application-brush-6-oz-tube/

1 user thanked author for this post.

Mike Uliasz

[Mike Uliasz]

Look like kit #2 for the after coolers, any other gaskets needed B4 placing the order?

[Mike Uliasz]

Going to pull the after coolers off next. My diesel mechanic buddy does not seem concerned that they have not been serviced in 5.5 years, but after reading thru some of your articles it sounds like a most do while going thru all the maintenance and one motor had a total rebuild in Nov of 2013 to due an O-ring failure and raw water getting into the motor. Appreciate the quick reply and noticed the twin engine kit was $180 for the works vs $49 x 4 just for raw water O-ring from Cummins. One motor run at 190 at 2200 rpm cruise and dropped right down to 180 at idle in 85 plus degree bay water. The other at 205 at cruise and dropped right down to 180 at idle. The heat exchangers had some build up on the lower half but were not stopped up. New impellers are in.
Thanks for the input.
Mike

[Tony Athens]

If it was me, I start fresh so you know what you have.. 50-50 brand name EG based coolant is cheap in the big scheme of things..

Are you doing the aftercoolers? Way more important ..

Tony

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