Before I cut a hole in my Boat......

[rick3452]

I've ruled out a list of things that may be causing my "high speed overheat" (thanks to the help from here)

im on the verge of installing a Buck Algonquin Though Hull Water Pic k up on my 2000 Mercruiser 5.0 with a Bravo 3. 1800 hours. I have done the following.
replaced Manifolds and Elbows both sides. (They had 1500 hrs on them)
Replaced impeller with OEM Mercruiser complete kit. (It was completely intact)
Replaced aluminum exhaust tubes (both)
Pulled off covers on Heat Exchanger fairly new and completely clear.
Power steering oil cooler clear
Thermostat opens right at 160 and stays there till I run the boat at 3800 RPM for several mins.
Then it goes to about 172/175. Throttle back and within a min or two right back to 160
Verified with IR Laser at hose going from outlet of thermostat housing to Heat Exchanger to be 172 when hot.
I've been reading a lot about "Bravo-it is" If I do choose the Through Hull route is there any negatives to using a Tee to connect the existing hose to work in conjunction with the new Through Hull?
Is there anything else that I am missing?
thanks so much!
Rick

 

[alldodge]

I don't see an issue with 172 to 175 running on plane with closed cooling heat exchanger.

I have open cooling and when I get up on plane I get to 170. Friend has twin 502 mpi closed cool and he stays at 180 on plane, no issue

 

[stonyloam]

I agree with the dodgeman. Acceptable temp range on my 470 with closed cooling is 160-200 F (and the 5.0 is a heck of a lot less sensitive to overheat than a 470) if the temp. Holds steady at 175 WOT, than I don't see a problem. It probably runs better at a little higher temp. After all your truck, with a closed cooling system runs at 190-210.

 

[Scott Danforth]

are you taking temperatures with a calibrated infrared thermometer, or from the $5 gauge on the dash powered by a $5 sensor?

Dash gauges are notoriously inaccurate. Even the smart-craft gauges rely on the same $5 0-5 volt sensor

 

[rick3452]

Yes using TWO inferred lasers, thanks

 

[Fun Times]

Based off of Rick's past topic titled "Question On Temp Rise" in the following link/quote below..... He seems to be looking at it as this is a new unusual event to where there could possibly be bigger problems just around the corner since he wasn't used to seeing the temp get to as high as mid 170's. That mentioned Rick, typically anything well over 179 degrees becomes a much higher concern.

Bear in mind that closed cooling systems do tend to run a bit higher temps vs standard cooling. Some closed cooling models use a higher degree thermostat too....I may be incorrect but didn't you just recently install this closed cooling system?

http://forums.iboats.com/forum/engi...273-question-on-temp-rise-2000-5-0-mercruiser

Hi guys, Serial # 0M012817 Half closed system with heat exchanger.
The other day I was cruising the intercostal with my family... I've had this boat 5.5 years and have put 1600 hours on it (now has 1800 hrs.) When I went to open it up within maybe three minutes the gauge went from the "constant " 160 to 180. I throttled it right back and within a few min, the temp returned to 160. This never happens... It had been 5 years and 1500 jrs since I replaced the Manifolds and Elbows so Yesterday I replaced both sides and took it for a ride. This time while running high RPM's it stayed pretty much at 165 but a few min later it rose to 170. So I brought it back and changed the Impeller including the new housing. There was 600 hrs on the impeller and it was completely in-tact I sort of thought that there may have been missing fins, but no. so when I take it out tomorrow and if it does rise.... What else should I look for? I have noticed on the Heat Exchanger hoses I have seen slight amount of green seepage.

Thanks as always for any help..
Rick

Before going with the thru-hull water pick-up, you may want to try and have a look at the gimbal housing pick-up fitting to see if it's clogged up. If you have access to an automotive inspection camera may help make things easier. I believe you can rent them if needed.

 

[rick3452]

Fun Times, thanks, I did replace the heat exchanger approx 2 years ago. And yes the reason for posting is in the 5 years of running this boat DAILY the temp gauge would barely increase. I do live on the intercoastal in Fort Lauderdale so typically cruising is just all we usually do typically the RPM is 1100 95% of the time it's only on occasion I will actually open it up just to maybe carbon out the carburetor .

 

[Fun Times]

intercoastal in Fort Lauderdale so typically cruising is just all we usually do typically the RPM is 1100 95% of the time it's only on occasion I will actually open it up just to maybe carbon out the carburetor

While I (& we) know that you know your boat pretty well just from reading your posts over the years as it did appear to read like you were able to use it pretty much on a daily basis but if most of it is at/near idle speeds, then just bear in mind that there is a small chance that just maybe you hadn't really had a good chance to completely notice the engine temperature increasing slightly while above 3800 RPM and quite possibly there just may not necessarily be something wrong as of yet and more/further testing, experimenting and inspecting should be done/considered to see just how hot it will go up to within reason.

Being that you run in salt, the clogged-up scenario on the bravo style inlet water fitting area is always a real concern and should be inspected especially in your/this situation until proven it's all okay in there....or not.

When was the last time the stern drive was removed to inspect the water passage areas of the drive itself and bell-housing area?
Was the impeller housing scored/grooved at all from sand, debris, etc.? If so, scoring could contribute to an increase in heat as well.

 

[rick3452]

Thanks again.... It has been quite a while since I had the out drive removed and replaced all the bellows and gimbal bearing. As for the impeller, there was no scoring and was in great shape....

 

[Bondo]

It has been quite a while since I had the out drive removed and replaced all the bellows and gimbal bearing.

Ayuh,.... The rubber parts at the transom only have an expected life of 'bout 5 years, or less,.....