View Full Version : 351 running hot mabey

06-30-2008, 09:13 PM
Ok trying to help out my mom and her Boyfriend. They have a 27ft 1973 Sea Ray with a Ford 351 model 233 engine ( not the original engine replaced in late 1990's)

It was over heating at the end of last season and they just put it away for the winter to deal with this year.

Mech at yard changed out the water pump and tubes in the out drive
Changed cap (electronic ignition)
New wires
New Plugs MR43LTS

Still overheating 180-200 at low RPM

I get involved,
I put new ex manifolds and risers
New 143 degree stat
New circulating pump
Oil change and filter.

Take it out and these are the numbers
1000 140
2000 142
2500 145
2600 160
3000 165
3500 170-175

Now for the Questions (trying to get technical answers from these 2 can be a trip LOL So I dont know what the numbers used to be.)

Are these normal Temp ranges for this engine at these RPMS ??
What Oil would be recommended for this engine???

Would the spark plugs make a difference????
The Original Spec for the motor was a MR43T

Right now there is a MR43LTS by the mech.
Looking up the spark plug numbers the one in there now has a longer reach then the original.

Would the shorter reach one make the engine run any cooler???
Should the engine run any cooler???

Thanks to all in advance.

06-30-2008, 09:21 PM
Autolite 24 is the usual plug for that motor, IIRC. If the raw water pump impeller fell apart, my guess is that some of the rubber is clogging the water passages, somewhere. The hole in the thermostat housing is pretty small and I have removed several pieces from this location in boats.

Have you looked at the oil cooler? If it has one (usually does), it's not easy to get to but it still may be clogged. After all, it's not a new boat. Does this boat live in the water or does it come out?

06-30-2008, 09:21 PM

06-30-2008, 09:59 PM
I'm confused. How is this boat's engine cooled? Where is the raw water pump?

Usually, it's belt driven and on the front of the engine, not in the outdrive. The impeller shreds, pieces plug up some of the internal passages, not enough water flow at higher RPMs. IMHO, your engine should run a constant temp at all RPMs. If it's not, you're not moving enough water through the engine.

I bring it up because I didn't see where you mentioned that anyone looked at or changed the raw water impeller.

07-01-2008, 08:24 AM
Thanks guys for the quick responses.
where would the Oil cooler be?? Didnt even think of that
When you say 'small holes' in the stat hoseing, in the top or the body of it?

The raw water pump is located in the drive unit itself
and was changed before it was dropped in this year. It stays in the water for the summer comes out in the winter.

07-01-2008, 08:44 AM
"The Original Spec for the motor was a MR43T"

Why would the original spec spark plugs for a Ford engine be a, AC Delco part? You said the original motor was replaced by the 351- the mechanic used the original motor's specified plugs on this motor? Get a new mechanic. First of all, if the OEM plugs were MR43T and he installed MR43LTS, he needs to do something else.

OK,. you say it has a drive unit- sterndrive, right? On a 27' boat with a 351? That's a lot of boat for a motor of this size. Since it's a Sea Ray, it has a Mercruiser drive. The water tubes may have been replaced but that doesn't mean they lined up. Also, if it was overheating last yhear and put away for the winter, it doesn't necessarily mean winterizing it did much unless it was drained instead of using anti-freeze.

07-01-2008, 09:34 AM
Well now you know how I got involved. They had it at this mech 3 times, 3 times they went to pick it up "everything is fine", and the last time they called me. I am NOT a mech but I am a littel "Mechanical". The first thing I noticed was the difference in the Plugs. Removed the port riser and end cap on the manifold as was like "Your Kidding me" Should have taken a picture.
I know the Original plug was MR43T.

As far as Iknow it was "winterized"

You mentioned the Stat Housing having a piese of the impeller stuck in it.
Is the Housing only a casting with ports and passages?? Are there any other parts in it besides the stat? Could the new stat not be seating properly and by passing when it shouldnt?

Any other place to look for a piece of the impler being stuck??

Thanks again for all your help.

07-01-2008, 10:16 AM
There's a responsibility for the mechanic that's implied when he charges for his services. This means that if the customer isn't satisfied, the servicer needs to make some restitution, either voluntarily or through the court system.

"I know the Original plug was MR43T."

Might want to call an auto parts store to cross-reference the plugs- I know the LTS is the wrong one.

The hole I referred to is in the cover over the thermostat. The large hose is attached to the top and the hole inside is usually pretty small. I don't know what your motor has, but it could have other hoses attached to it. If a thermostat isn't seated and the water bypasses it, it's not going to run hot- it'll run cool.

What to look for depends on the path of the water, the condition of the motor, where it's used and how it has been maintained. If the water going in tends to be silty, the block may have a buildup in the water jacket. The oil cooler, if it has one, will be inline when you inspect the raw water hose going to the motor. If it has an oil cooler, look for two hydraulic lines going to a black painted tube that may have some brass showing, from the paint coming off. Usually, it's on the port side of the motor.

What does the oil look like? Clear and normal or is it milky, at all?

Again, if you can post some clear photos, it will make life easier.

07-01-2008, 10:26 AM
Thanks Jim, As far as them taking it up the mech.They will have to decide what they want to do. Im just trying to keep them on the water for whats left of the summer.
I wont be back to the boat until Sat when I will change the plugs,
I have the origanal MR43T on order
and open up the stat housing and take a look in there and see whats going on.
And your right , a picture is worth a thousnad words.

07-01-2008, 05:55 PM

07-01-2008, 08:50 PM
No not gone yet. Getting the parts together for this weekend. and will post any all results good bad or indefferent. i appreciate the help and will return the favor when i can.

in the meantime im bringing new plugs, orignal mr43t new sending unit, miss hose connections for flushing etc. heat temp gun, new gasket for the stat housing wrenchs ,tools coat hanger lol

Am i forgetting anything

07-01-2008, 08:58 PM
You're welcome.... :rolleyes:

Newbs sign in, get a fix, and gone... LOL... :Insertmiddlefinger:Gee...speaking of noobs, that was kind of rude. Especially from a long-time veteran TMC poster like yourself.

07-01-2008, 09:07 PM
No not gone just getting the parts together for this weekend.
I apprecicate all the help and will report any results.

In the mean time I bringing miss hose fittings for flushing, new gasket for stat housing, origanl plugs mr43t, feller gauge, wrenchs etc, and a coat hanger lol and a new sending unit and a temp gun I can borrow from work just because , after all this can it be the sending unit is 10-15 degrees off after being overheated a few times????????? what should the resistance be for 160 on a (I think a stiger gauge)

am i forgetting anything.

07-01-2008, 09:11 PM
thanks Big Mac

07-01-2008, 09:18 PM
Make sure the MR43T is right for that engine. I don't have a chart, buy IIRC, the 24 or 25 is the right one for a 351 Ford motor. If it crosses as correct, go ahead. The sender won't keep the motor from starting unless it's injected. Get a set of plug wires if the ones in it are more than three years old.

If you can, and since you're planning to flush it, get a fitting for the block where the petcocks are, then flush the water jacket on both sides. Let the water rush out and look for silt, etc.

07-07-2008, 07:25 PM
Ok guys this is what I found. Some were along the line someone spliced in a plumbing check valve and some nipples and a tee in the hose from the stern drive pump to the circulating pump to add a fresh water flush to the engine. Removed the set up and the flapper in the check was broken and stuck. So at low rpm you had flow but when you got it going not enough water was being passed through. The set up was probably 20 years old. My friend has had the boat for that long and it was always there. NOT FACTORY INSTALLED. So at WOT 165 temp. But once again I forgot the camera, so here is a really bad line drawing of the set up.
Thanks for all the help guys, I do Appreciate it.

07-07-2008, 07:30 PM
Cool. Glad you got it figured out.

07-07-2008, 08:26 PM
I wouldn't have any plumbing parts between the fresh water inlet fitting and the oil cooler or raw water pump, depending on which comes first. Nothing that causes the diameter to decrease would ever go in my boat. No check valves, no splices/barb fittings, no shut-off valve. Anything that disrupts the flow will cause cavitation at high flow rates and that introduces air, which doesn't help cooling.

07-08-2008, 08:25 PM
The new hose in on order, While im waiting I get a call, now the stater motor is gone. The only upside is with the hose is out, it will be easier to do the starter.
Down side while the manifolds were off it would have a LOT easier

If you want to talk sabatoge get this one

I research the right plug for 3 days everything and everyone including NGK direct tell me MR43 short reach plug is the plug.
why use MRL43t long reach. Go to change the plugs and they dont fit
put thel old plugs back runs fine. Reasearch alittel more and find this post

I purchased an used 302. Was told it came out of 88 mustang. It is a 5.0 EFI. Rebuild done and am placing it in my 83 F100. Heres my problem. I went to parts store picked up some Autolite double platnimum plugs for it and they dont fit. Had them check again the part number for both mustang and f150 in the 88 time frame and shows that autolite app24 or app25 is the right plug. However, they do not reach the threads in the head. It is as if the lenght/depth of the plug is not long enough. Any ideas would be great.....

That means you probably have E6S heads. Those take APP2545 plugs. The E6 is the 86 swirl combustion chamber head. It was only used on the Mustang HO motor in 1986. It was also used quite extensively on regular passenger car 302's such as Crown Vics...ect.. during the late 80's.

Guess what Its not a 351 its a 302 The 351 was the other boat i had He tells me.

The moral Senior citezens gotta love them

thanks again guys