View Full Version : Used Boat Engine work

04-01-2010, 11:52 PM
I purchase a used boat recently and want to do a overall engine tune up and just want to make sure I am in line. :)

91' TriStar w/ 351 V8

Spark Plugs - Can I go to Autozone and just purchase the nice platinum ones or do I need special marine ones? If they are special, whats the "premium" brand make or model?
Air Filter - Special type I assume due to the wet enviroment?
Fuel Filter - Special type I assume due to the wet enviroment?
Replace Oil - Has 400 hours. I am a castoil Synthetic guy. 10w 40? or do i need to use a marine rated oil?
Transmission Fluid - I would assume replacing the fluid is a bad thing just like on a car with high mileage... If its not broke, don't try to fix it. Just make sure its not milky or black?
Coolant - My engine has a coolant tank... so I assume pulling the hoses and flushing it with a garden hose in both directions is ok?
Engine Cosmetics - The engine looks nice and clean, but there is some rust on the exhaust manifolds and also the chrome plated pulleys have some rust. Any particular way to go about cleaning it up and re-painting to seal it from future rust? Do I need to use some special high temp blank paint?
Carb/Idle - I don't think the carb needs to be rebuilt. It starts up without a hitch and idles just fine. Its been on the lake once and seems to be getting fuel for sure. Is there any small stuff I could do or clean without rebuilding or simply spraying carb cleaner in it?
SeaFoam?... Anyone use this? I use it in my car a few times a year.
Running out of water ... I have no pretty hose connection to the engine, so I assume I would be fine cramming the water hose in the intake on the bottom of the boat and ensuring the most amount of water it flowing into it?

(Breaths) What a mouth full.... If theres anything I am missing I should do as a new owner to the engine, trans or anything, feel free to add in.

Thanks in advance!

east tx skier
04-02-2010, 12:16 AM
Welcome, Mike. Where in TX are you?

Go with the copper plugs. Skip the platinum. Auto parts store or WalMart is fine. Autolite is my preference. I think it's the AL24 for your engine.

No air filter. Just remove the flame arrestor (metal filter over your carb). Take it away from painted things, children, or painted children ;) and spray from inside out with carburetor cleaner. Let it dry completely before reinstalling.

Both fuel filters can be purchased at NAPA (assuming two --- one canister and one spin on fuel/water separator).

Skip the synthetic. Intervals are 50 hours or seasonal so you don't need the lengthy protection. I prefer Valvoline VR1 20W50. It has the proper levels of ZDDP for your flat tappet cam. Not sure about Castrol. Do a search for ZDDP and you can read more about this.

Dexron III or IV or Mercon. Replace every year. Pump it out and replace with the same amount you took out. Milky pink is bad. Not like a high mileage car.

If you have closed cooling, I'll leave that for someone with experience with that sort of thing.

Don't repaint your exhaust manifolds. They all rust. Paint could actually make it worse the way I understand it. If you want to knock the excess off with a brush, go for it. A little silicone lubricant at winterization and always propping up your motor box when you're not using the boat to increase circulation will go a long way in helping keep this to a minimum. As for the pullies, you may want to investigate this further. That rust may end up working on your belts over time. I've seen a touch of rust on pullys, but have not worried about it much.

A half of a can of SeaFoam in the carb and the other half in the gas tank. Kill the boat and let it sit for 20 minutes. Crank it and drive it like you stole it for a while.

See previous answer.

Not sure about closed cooling systems, but the hose at the low point works. My preference is to remove the intake hose south of the transmission cooler (or add my own hose to the south end of the transmission cooler) and put it in a 5 gallon bucket full of water that's fed by a garden hose. That way, the engine pulls the water it needs and I always know that it's getting enough.

Lots of good info on this forum. Don't be afraid to ask. Good luck with the new boat.

04-02-2010, 09:10 PM
I'm in Houston, Texas, east_texas_skier.

Well I got a good start today. Had to go the store a few times for random things, but since my engine doesn't have a faucet connection, I found some pipe that fit right on to the water intake so i could warm it up for an oil change. Have two issues...

The first device, which I assume is part of the transmission cooler I believe is leaking. The transmission fluid was nice and pretty before I warmed it up, but after about 5 min when I killed it to drain the oil I checked the trainny to see a strawberry milk shake! Am i correct in my assumption? Is there any way to test rather than fill it back up with good fluid and just let it go to waste by water mixing? I assume I just need something like so: http://www.skidim.com/prodinfo.asp?number=R147005

Also when I removed the floor board & engine hatch to do some cleaning I noticed one of those hoses (3 or 4in) is falling apart & it had a piece of PVC strapped to it. (I will get a picture tomorrow.) I assume this is an air intake hose?

east tx skier
04-04-2010, 10:57 PM
Where did you hook up the hose? You can stick a hose into the intake line. However, my preference is to drop the intake hose into a bucket fed by a water hose. Let the engine draw what it needs.

Sounds like water in your transmission fluid. I would figure R&R it a couple of times unless there's an obvious leak, in which case, replace the part and R&R the fluid a couple of times.

That hose with the PVC in the middle sounds like your blower hose. Definitely want to replace that. Dryer hose works surprisingly well in my experience.

04-07-2010, 12:03 AM
I'll add my welcome. I have a 91 Tristar as well.

Sounds as though your boat didn't come with the Owner's Manual. Not surprising. You may want to download one here http://www.mastercraft.com/knowledge/owners_manuals/ from the MC website. It has some good info re: tuneup specs and maintenance tasks.

There are guys on this site like east tx skier who have forgotten more than I'll ever know about MC boats. Ask lots of questions.:)