1987 268 da temp question

[gasamp]

Anyone have any idea what engine temp usally runs on these boats? I bought mine late last summer and the origional temp guage is not easy to read goes from 170 to 220 in a1/4" space. When I just putt arround (about 2000 rpm) it is about 170 But when planeing (between 3500 to 4400) it seems to be near 200 but never seems to overheat) It is a 454 330 hp have new impeler heat exchanger is clear and exhaust was done a few years ago. Also what would be the best rpm for fuel consumption.

 

[Wee_Isle]

I have an 87 350cid with omc outdrive and it runs a constant 170 at wot stock motor with 650hours
Best RPM for gas consumption would be slowest RPM to keep it plaining and trimmed out.

 

[Matt89GT]

what thermostat are you running? 140º? 150º? 160º?

 

[popeye]

Anyone have any idea what engine temp usally runs on these boats? I bought mine late last summer and the origional temp guage is not easy to read goes from 170 to 220 in a1/4" space. When I just putt arround (about 2000 rpm) it is about 170 But when planeing (between 3500 to 4400) it seems to be near 200 but never seems to overheat) It is a 454 330 hp have new impeler heat exchanger is clear and exhaust was done a few years ago. Also what would be the best rpm for fuel consumption.

I have the same eng/outdrive as you. At idle with muffs sitting on the trailer =145, at cruse 160-170....Since I am new to this boat as well not sure if that's normal or not...What I know about BB Chevys that's an OK temp.....If anything it might be a little low...:thumbsup:

 

[300 Ray]

Even with a 170 stat ,(which it probably has a 145) It shouldnt be approaching 200. Its not really hurtin the motor at that temp but its not right. If you can get ahold of an infrared heat gun I would try shootin each manifold and see if you have a drastic temp difference bank to bank. If they are within 5deg.or so of eachother I would start lookin at thermostat or the supply to the engine. Who knows maybe someone stuck a 195 auto. stat in it?? Dan Ps I have seen the rubber supply hose that comes through the transom become the cause of this.

 

[gasamp]

Thanks guys I will try and check with a heat gun I think the temp gauge is just crap and hard to get a true reading.

 

[richard3rd]

Hey gasamp you've just described the exact problem I'm having on my 87' 268 DA w/a 454 mercruiser. It make me nervous that it gets that hot. Also how quick does yours climb? With mine it's instant. I'm a Ford Man, so this is my 1st GM based product so I'm a little lost at what's the normal for this setup. Any experienced insight on this would be greatly appreciated.

 

[gasamp]

I know there are several factors to concider. First both the raw water and engine pump working correctly. The heat exchanger , and exhaust manifolds should be clear and flowing free. The thermistat must be right temp and opening at rated temp. Intake must not be obstructed ( mussles barnicles etc)
I am going to check temp with a heat gun as I feel the guage may be incorrect and is also hard to read. I have a 155 stat After warm up it idles about 170 on the plane seems to read about somewhere between 180-195 but as I say the factory guage is not calabrated as to get a good reading. I have ran up and on the plane for 1 or 2 hrs at a time and have never overheated. Others seem to say they are runing cooler. I will post after my heat gun readings.

 

[88dancer300]

I had a 1987 268 sundancer with the 454 and Alpha drive. I had the same issues when running at anything over 4000 RPM. We dissmantled the whole cooling system, installed new risers, boiled out the manifolds and cooler, changed out the thermostat, installed new drive impeller and installed a new circulating pump. Still had same problem at higer RPMs. Up to 3800 RPM, it would run all day at 145 degrees. After much research talking to Merc and sea ray reps. I found out that one of the reasons searay stopped using the Alpha drive, aside from the fact that people were tearing the top gear set out of them, with the 454 motor was the impeller in the drive could not efectively supply the 454 engine with raw water at higher RPMs. I have met a lot of others with the same issues. The one thing I was told I could do to solve the problem, was to install a stand alone raw water pump that runs off the pulley. Note: most of the big blocks in this vintage boat came though with the double belt pulley on the damper. I bought the pump and through hull, but sold the boat two months ago, and never got to install it. I am going to keep the pump as a spare for my 300 sundancer.

 

[gasamp]

Great info may look into stand alone raw water pump that is what I had on my last boat a 32' trawler style diesel ( too slow) and it ran real cool. I am going to remove T stat. and see what that does.Thanks for the feed back

 

[BonBini]

One thing to consider before you go reworking a cooling system that has worked for 23 years. Be sure your block isn't plugged up with rust sediment. Also be sure your not over propped and check that coolant regulator. Mine seems to run at a consistent 150* Pushing 40 mph the temp will slowly creep and stabilize close to 200*. I don't believe there is anything wrong with my boat. I do think if I push it I will blow my drive for sure.

As far as fuel consumption while on plane: That’s gota be the slowest speed where the hull runs free through the water. My weekender feels good around 25mph - 30mph.... just my .02

 

[dirty dave]

My 89 with a 7.4 and bravo 1 runs 145 to 155 all the time.

 

[BonBini]

Update: I have since changed out my lower water pump. The impeller looked good, however the side thrust sealing area was burnt and warn looking on the housing. My temp now runs rock solid 145* no mater how I run it.

 

[KatzNDogs]

I owned this setup for eight years. Same issue. I bought an engine mounted raw water pump off ebay and put in a thru hull(1 1/4"), valve, and strainer. I then routed the drive pump water out the transom thru another discharge thru hull. Never ran over 143-145 again.

The Alpha pump just can't push the water needed.