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skilew
03-15-2005, 08:12 AM
I got such good advise from my last post about a carb problem I thought I would ask the experts out there about this issue.

Is anyone using synthetic oil? I have a 1993 Ford 351 engine with the GT-40 heads. What is the recommended weight oil for this engine and is it ok to use synthetic oil?

Also need to know what temp. thermostat to use.

Thanks,
SkiLew

André
03-15-2005, 08:21 AM
If you do your regular oil change at 50 hrs,no need to go synthetic in my mind.
Not sure about the tstat but i'm lthinking 160.
Oil grade is 15 w 40 marine grade but that's not mandatory.

rem_pss308
03-15-2005, 08:23 AM
I also have the gt-40 351, I use mobile-1, I the weight I use is 50 I cant remember what the lower number is. it is either 5 or 15.
I was running a 140 thermestat, but the guy at SKIDIM.com said that they were geting better results with the 165 thermostat

Since I have installed it, I have not had any problems.

Tex will give some input also, He has the same engine as well.

ski_king
03-15-2005, 08:43 AM
I remember a somewhere back in the 92 to 94 range there was a year that MasterCraft/Indmar/Mobil had a special engine warranty as long as you used Mobil1 oil.
Does anybody else remember this?
If so, how has it worked out?

Professor
03-15-2005, 09:50 AM
I’m using Castrol/Syntec 5W-50 in my LT1. My summer temps approach 100 and I like the high ambient temperature limit of this oil compared to the “dino juice” oil I used. The synthetic oil is without a doubt better, but what is more important is changing oil/filter on a regular schedule. Of course, I think the oil is less of an issue than what is in the oil. Engines not used on a regular basis will introduce water from condensation into the oil (white sludgy ‘gook’ sometimes seen under the oil cap). In addition, regular oil changes removes acid and contaminates. There are several factors to consider to determine the type of oil: engine age, environmental conditions, use, etc. Keep in mind for every person you ask this question to you will receive a different answer. Oh, I forgot…I realize the earlier synthetic oils had a tendency to induce leaks because of the small molecule structure but swelling agents have been added and I believe do a good job. I will let someone else answer the OEM 351ci questions…

east tx skier
03-15-2005, 10:16 AM
According to my conversation with Indmar last summer, they're currently recommending Pennzoil Marine Grade 15W40 for the 351W HO (GT40) among other engines. Your manual recommends Mobil1 SAE 30. Brand, of course, isn't so important. It's just who Indmar has the sweetheart deal with.

6ballsisall
03-15-2005, 10:38 AM
I got such good advise from my last post about a carb problem I thought I would ask the experts out there about this issue.

Is anyone using synthetic oil? I have a 1993 Ford 351 engine with the GT-40 heads. What is the recommended weight oil for this engine and is it ok to use synthetic oil?

Also need to know what temp. thermostat to use.

Thanks,
SkiLew


How many hours on the boat?
I have had great luck in the past with Amsoil. One word of caution, if you are putting it in a high mileage engine you do run the risk of creating new leaks (or leaks in general) I ran it in a 78 Bronco that only had 80k miles (400 modified) It did not leak before synthetic but it did develop several leaks afterwards. Synthetic acts as a cleaning agent and will get all the junk and buildup out that was created by the dyno oil. Also, if you do, I would recommend using an oil cleaner to get at as much of the old dyno oil as possible. Good luck and if let us know how it works out for you!

Footin
03-15-2005, 10:48 AM
I was going to use Mobil 1 in my 94 205 with 410 hours, should I be concerned about leaks? I was also going to use Mobil synthetic trans fuild in the trans. I have heard from a more than one source that this may add a small amount of HP and the trans will operate smoother.

I will continue my 50 hour oil changes with whatever I use.

6ballsisall
03-15-2005, 10:52 AM
I was going to use Mobil 1 in my 94 205 with 410 hours, should I be concerned about leaks? I was also going to use Mobil synthetic trans fuild in the trans. I have heard from a more than one source that this may add a small amount of HP and the trans will operate smoother.

I will continue my 50 hour oil changes with whatever I use.

Its really hard to say about the leaks, just something you need to thinkabout.

I don't claim to be the expert on the subject but I can tell you I really don't think you will see HP gains from the oil change. However, endurance, the integrity of the engine could get better with a good synthetic. I will tell you I have a friend who just switched his Cummins 6 speed over to synthetic, the shifting characteristics (the speed you can throw the shifter and the accuracy) improved ten fold. I think you will be pleased with that with the transmission, I am going to change my transmission over when it is broke in.
My motor will still get dyno oil until I can tear it down and build a new beast. Then it will get Amsoil

skilew
03-16-2005, 12:21 PM
How many hours on the boat?
I have had great luck in the past with Amsoil. One word of caution, if you are putting it in a high mileage engine you do run the risk of creating new leaks (or leaks in general) I ran it in a 78 Bronco that only had 80k miles (400 modified) It did not leak before synthetic but it did develop several leaks afterwards. Synthetic acts as a cleaning agent and will get all the junk and buildup out that was created by the dyno oil. Also, if you do, I would recommend using an oil cleaner to get at as much of the old dyno oil as possible. Good luck and if let us know how it works out for you!

I have only 300hrs on the boat. I also wanted to ask if anyone uses an additive like SLICK 50 or STP?

6ballsisall
03-16-2005, 12:26 PM
I have only 300hrs on the boat. I also wanted to ask if anyone uses an additive like SLICK 50 or STP?

Personally I think that stuff is unneeded. Years ago my parents had an RV with a Chevy 350 in it that was really tired, they put Slick 50 in it to keep the knocking down and prolong the inevitable rebuild. It did help there (at least killed alot of the sound) If you only have 300 hours on your boat and there isn't problems I think you would be wasting your money completel.

86PowerSlot190MC
03-16-2005, 01:53 PM
I got such good advise from my last post about a carb problem I thought I would ask the experts out there about this issue.

Is anyone using synthetic oil? I have a 1993 Ford 351 engine with the GT-40 heads. What is the recommended weight oil for this engine and is it ok to use synthetic oil?

Also need to know what temp. thermostat to use.

Thanks,
SkiLew


Looking at the engine sticker and an old ford manual on the 351 Windsor engine, I use 10-30w Castrol Syntec Blend.

Last Sunday the engine was running at 175, maybe 1-2 above on hard runs. So I guess I’m running a 165 thermostat, but keep in mind I have closed cooling.

NatesGr8
03-16-2005, 02:16 PM
Closed cooling huh, how'd you accomplish that? I sometimes am forced to run in salt water and would like to integrate closed cooling into my rig.

east tx skier
03-16-2005, 04:26 PM
Closed (Fresh Water) cooling systems were optional in 1993 (and perhaps earlier).

86PowerSlot190MC
03-16-2005, 04:53 PM
Closed cooling huh, how'd you accomplish that? I sometimes am forced to run in salt water and would like to integrate closed cooling into my rig.

The previous owner installed the system, it's only the half system, but new exhaust manifolds are cheaper than an engine block.

Here is some info:

http://i-netmarine.com/fwc/fresh.htm
http://www.cpperformance.com/detail.aspx?ID=3112
http://www.oceaneastmarine.com/freshwater2.html

They’re not cheap!!!

NatesGr8
03-16-2005, 06:47 PM
Thank you very much, that is something that i will be looking into for the end of next season. Have you had any problems with the closed loop system?

86PowerSlot190MC
03-16-2005, 07:01 PM
Only a couple of leaks. One on the threaded plug in the end of the heat exchanger and one on the pipe work from the raw water pump. I have to clean the raw water strainer every couple of trips out. You’ll be amazed what collects in there (wood, plastic and half the beach!!). And there’s one more level to check under the engine cover!! But apart from that no hassle at all.

Hoosier Bob
03-16-2005, 07:55 PM
The owners manual says "SAE30/AP1SF. Mine was sold with MOBIL1 and has 2yr Warranty stickers on the engine "LIMITED" My boat has had M1 since new but the Indmar/MasterCraft Power manual says:
Use SAE30 oil at all times. Non-detergent and other low quality oils are not recommended. They recommend every 50 hours. Walmart has Mobil1 for around $19.00 for 5 quarts. Seems cheap enough if it just so happens it's better. I would go Mobil1 15/50. 15/50 should not leak as it is a pretty heavy weight oil designed for warm weather (boating temps). If you use your boat in extreme weather (Winter) get better advice. No additives yet for me. Change your oil often. It is very cheap insurance.I have only 300hrs on the boat. I also wanted to ask if anyone uses an additive like SLICK 50 or STP?

costal190
03-16-2005, 08:15 PM
A great site to go to for info. on oil is : The MotorOilSite.com
It will give you all the info. on any kinda oil you can think of. I am a firm beliver in synthetic oil because I have seen it first hand out perform natural oil. I use it in all my vehicles and have been for 10yrs.
I ave a 1995 Prostar 190 an I use 76 Lube. SAE 20W50 with an AC Delco filter. Excellent Results, No Oil Leaks. My motto is why scimp on something that doesn't cost a lot, good oil, plugs, good filter. They are the cheap things that make others more dependable.

bkblaida
03-16-2005, 08:53 PM
There are now many brands of synthetic oils on the market. Take the time and call their 800 numbers and ask about marine use. The difference is a marine rated oil is formulated to tolerate water contamination. Amsoil and Mobil 1 have been tested and proven in marine use. (however not all Amsoil products are rated for marine use)
One key difference in synthetics vs dino oils is dino oils breakdown slowly where as synthetics break down all at once. However under almost all conditions the engine will give out before a synthetic will break down. Another advantage not always realized in a boat is the viscosity stability in a synthetic. When I lived in MN we used Mobil 1 in our cars and at 20 below 0 the viscosity held to the 5 weight vs getting thicker from the cold and our cars turned over like summer time. My neighbors with dino oil always had problems cranking their cars over. The same will hold true in extreme heat....the dino oil will start to break down and thin out where the synthetic will keep its upper number rating to at least 600 degrees.
To add more discussion and confusion in the above comments, new high grade dino oils are so good, that keep them clean and changed often and your problems will probably never be oil related.

Regarding Slick 50 - Popular Mechanics has run many tests on teflon oil additives and the results are always the same. No need to use if you use a good grade oil and filter and change often. The molecular size of the teflon is smaller than the engine tolerance, hence it does not build up and lubricate as claimed. Save your money. ;)

Chicago saw 50 degree's today so summer is within...... oh two months!

bret
03-16-2005, 10:12 PM
I race Porsches on the weekends and with regards to Mobil 1, we've heard some disturbing thinning of the oil in the past two years - since the "merger". I run Castrol 20/50 in the boat and have since 94, I took the Mobil 1 out when I got the boat home from the dealer. Synthetics do not seat rings in worth a darn, I just don't like it for break in oil...and that's just my opinion from building engines. We break in engines with 30 wt, ND cheap dino oil for 200 miles to seat the rings.

I agree that if you change the oil every 50 hrs, synthetics are really not needed but if I did run synthetic, it would be Castrol. If you have an older boat and switch, yes leaks are possible, mostly due to the sythetics removing some older deposits around seals.

The past three race weekends, we switched to Valvoline 20/50 racing in the race car. We have a catch can that gets oil from the crank case breather assy, instead of going back to the turbo. We used to run 15/50 Mobil 1. The catch can would fill up 3/4 full on a weekend of hard racing. The engine has as new compression and less than 2% leakdown. On advice of a trusted person, we switched to Valvoline racing. The past three race weekends, the catch can has barely had 2 tablespoons of oil in it all weekend.

Anyway, I think Mobil 1 was a better oil before the merger of the companies.

prostar205
03-17-2005, 01:11 AM
During my discussion with Indmar today regarding the weight of oil to use in my L-18 engine, they have changed from 15W-40 to straight 40W.

Does any of the sythetic oil manufacturers make a straight 40W synthetic oil? Indmar said synthetic was fine as long as you were past 100 hours but they stressed staying with a 40W grade.