1995 7.4L Thermostat

TBarCYa

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I finally put the boat in the water and ran the engine for more than a few minutes and found that the temperature never goes above 140 degrees. Now, I never really was above idle but even after idling for 10 minutes it never rose above 140.

My guess is that there's no thermostat in the housing but I haven't pulled it apart yet to see but is it possible that it's got a 140 degree stat? I'm in the process of tweaking the choke to get it to completely open when the engine is warm but if it only gets to 140 I don't know if that's hot enough to fully open the choke anyway.

Thanks.
 

alldodge

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If you have a carb motor then it came with a 140 degree thermostat.

If your in fresh water you can change to a 160 but not necessary
 

thumpar

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A 143 is pretty common. I run a 160 and have never timed it but it does take a bit to warm up. If there is none in there you will want to install one.
 

Bt Doctur

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and you choke may be electrically operated not bi-metal housing operated
 

harringtondav

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I'm guessing you have a 140 deg installed. Occasionally mine gets blocked open with sand, etc after I back off a beach. Then I never get over 110 deg. 10-15 sec at WOT flushes it and I'm back to 160 deg.
 

TBarCYa

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Yeah it definitely makes it to 140 but I'll double check it tonight. My choke is bi-metal spring operated but I may consider an electric upgrade since this thing is for the birds.
 

thumpar

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Yeah it definitely makes it to 140 but I'll double check it tonight. My choke is bi-metal spring operated but I may consider an electric upgrade since this thing is for the birds.

Someone must have switched the choke. Even my 1983 had an electric choke. The ones that I have seen with bimetal had a tube from the exhaust to heat them and it was old.
 

aimlow

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Your t'stat must have a small bypass hole in the flange to allow water to circulate past the t'stat and warm it up quickly.
 

Lou C

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If the boat has a 140 stat in it your temp may be normal. I find that with a 160 stat in my OMC it usually runs between 155-160 at idle and at most it will touch 175 after coming off plane but then cool back to 160 after slow speed running or idling. Get an IR Temp gun and check your readings, on the intake manifold right under the 'stat housing. This I find seems to corelate closest with the dash gauge reading, usually it's about 10* lower.

About the choke, I have had both the intake manifold heated choke (Rochester) and electric (Holley) my experience with them has been that the intake heated choke takes a long time to open unless you are actually running it on the water, if just idling on the water hose they take forever to open all the way. The electric chokes open almost too fast, they are just responding to the voltage applied to the choke heater and not what temp the engine is actually at (as do the intake heated chokes). You can in some cases convert to an electric choke but if it needs a full 12V to open it, keep in mind you will need to find a terminal on your alternator that provides 12V with the engine running, but zero with the engine off, even if the ignition is still on.

Also if you can get one for your engine, you can put a 160 stat in it, for OMC/Volvo engines that's all that I have ever found and I have not had overheating issues with the 160. Keep in mind that these auto based engines were designed to run much hotter (it 195* stats, so running temps of 195-210 or so are typical). However, in an open or raw water cooled engine which is what most of us have, due to the fact that the cooling water is not pressurized, you cannot run that hot, because you could get localized boiling in the hotter parts of the cyl head (ie like near the exhaust valve seats) if you were running that hot. The pressure cap in a closed system keeps that from happening.

Keep in mind that when we drove carbed cars, a normal part of the yearly tune up was cleaning the choke plate, pivot points and linkage. If they get dirty the choke spring may not be able to open it all the way. So before you change to an electric choke, clean up what you have, and see if that helps it to open.

Personally I'd rather have a manual choke on a marine engine due to the issues noted above, but the available conversion kits are not good quality.
 
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aimlow

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If the boat has a 140 stat in it your temp may be normal. I find that with a 160 stat in my OMC it usually runs between 155-160 at idle and at most it will touch 175 after coming off plane but then cool back to 160 after slow speed running or idling. Get an IR Temp gun and check your readings, on the intake manifold right under the 'stat housing. This I find seems to corelate closest with the dash gauge reading, usually it's about 10* lower.

About the choke, I have had both the intake manifold heated choke (Rochester) and electric (Holley) my experience with them has been that the intake heated choke takes a long time to open unless you are actually running it on the water, if just idling on the water hose they take forever to open all the way. The electric chokes open almost too fast, they are just responding to the voltage applied to the choke heater and not what temp the engine is actually at (as do the intake heated chokes). You can in some cases convert to an electric choke but if it needs a full 12V to open it, keep in mind you will need to find a terminal on your alternator that provides 12V with the engine running, but zero with the engine off, even if the ignition is still on.

Agreed. Heat well chokes in a marine environment rust up and fail. On most heat well chokes on street applications, there was a heat sensitive flapper on one exhaust manifold which closed when cold and forced hot gasses thru the heat crossover in the intake manifold which resulted in faster warming of the intake manifold.

Some electric chokes run thru an oil pressure sensor, so they only get current when the engine starts.
 

Lou C

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I have also seen aftermarket ones sold on quadrajetparts . com, that use a temp sensor that bolts to the intake. This may be better than the Holley style ones that tend to open a bit too fast.

Is this a Merc or Volvo engine you are talking about?
If Merc, then it should have a Weber carb and electric choke.

http://www.crowleymarine.com/mercury-outboard/parts/1621_140.cfm?mdl=LGBZIB

If a Volvo, then same thing, electric choke on a Holley 4160 it looks like to me....

http://www.volvopentastore.com/Carb...on_id.297196225--store_id.366--view_id.778981

So if your choke is not working, then its either a bad choke coil or bad wiring to the choke coil. Check for 12V with the engine running at the choke positive terminal. Of course the other terminal must have a good ground. When these work, they open fast like in 3-5 min at most.
 
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TBarCYa

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I haven't had her out of the slip yet but it seems like the old school choke works just fine as long as I get the linkage adjusted properly. I'll probably check again tonight before taking her out this weekend just to be sure that it's adjusted right.
 

Scott Danforth

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Your t'stat must have a small bypass hole in the flange to allow water to circulate past the t'stat and warm it up quickly.

Not needed on a BBC. there is a 1/2" diameter bypass line from the manufacturer.
 

aimlow

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Not needed on a BBC. there is a 1/2" diameter bypass line from the manufacturer.

The hole allows hot water to circulate better and melt the wax pellet sooner..sometimes the t'stat sits in a somewhat uncirculated water mass, even tho there is the stock bypass.
 

TBarCYa

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Hey Scott, we're taking her out for the maiden voyage on Sunday and if all goes well we may be heading in your direction. Are you a true FL boater that stays off the water after Columbus Day or might you be on the water this weekend?
 

Scott Danforth

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Hey Scott, we're taking her out for the maiden voyage on Sunday and if all goes well we may be heading in your direction. Are you a true FL boater that stays off the water after Columbus Day or might you be on the water this weekend?

Im sanding the hull getting ready for gel coat this weekend (thread in my sig). may be out in my buds boat. once the boat is back in the water, It usually gets used every other weekend unless there is a small-craft advisory
 

TBarCYa

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That's a heck of a project you have going on there.... I need to replace half of the windshield in the Proline and am debating freshening up the frame... But I'm too anxious to get her out of the slip to do that now. Hahaha
 
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