Another BF150 High Temp Question

I have two almost new 2018 BF150s with just under 100 hours. The engines run great - especially around 4000 rpms. So here's the issue/question. My gauges are the VeeThree NMEA-2000 gauges, but I always use my Simrad Go9. Why does the temperature always report so high (on both V3 and Simrad)? I usually run around 4000 rpms, and the temp is usually around 195. When push things harder, like 4700-5000 rpms it will eventually work it's way up to 215-220. I have gotten the alarm to sound on a couple occasions when making long runs at the higher rpms, and i just turn things off, wait a couple minutes - and I'm good to go. It's only happened like 2 or 3 time. So I just keep things around 4000 rpms (where I've never gotten an alarm).

It seems like other people have run into this issue, and they have had issues with the relief valve. Being such a new engine (and me being the first owner), and not having any overheat alarms (except for the couple of times where I made a long run at higher RPMs), I'm doubtful I have any issue with the relief valve or thermostats or even the impeller.

So what exactly is up with this and the high temp getting sent over NMEA-2000 and to the Simrad? I wish i new what the correct temp was for this be running at (over NMEA)?

Juice

Your motors should not go over 210F at full throttle and sit around 190 cruising 3500-4500rpm. Change your thermostats, they should be done annually or every 100hrs. Make sure you fit the 50 deg nearest to the cyl head ie furthest from you sitting in the boat. You will find the block thermostat builds up a lot of salt (assuming you are operating in saltwater)

Thanks iang. I'll change out the thermostats and see what happens. And yes, I'm in salt.

Changed the thermostats, but it's been so windy lately that I haven't been able to get out and run the gulf at higher rpms (like 4500-4800) to see the result. What I did notice in my limited testing was I'm still showing temps at about 200 on the Simrad (over NMEA200) while running as extended as i could around 4000 rpm.

My guess is I'm either getting a bad number from NMEA (as I'm getting no alarm) or maybe the relief valve needs changing?? I have a service manual, but curious how difficult it is to change? I have the repair manual, and it looks like that part is kind of low and buried. Wondering if I need to remove the plastic housing to get to it??

You should really have your engine checked with DrH to see what is going on. They are obviously under warranty, so I would do that, it's hard to diagnose an issue like this without actually running the boat and doing a proper diagnosis. Carrying out work other basic service items could void your warranty.

That would be ideal, but it's nearly impossible to get my boat to a Honda certified mechanic with all the boat ramps closed. Carrying out basic - actually any - work does not void a warranty. The Magnussen-Moss Act is explicit in allowing work to be performed by anyone. Car dealers are notorious in misleading customers into thinking they need to bring their cars to them for service (not even repairs), otherwise it will void their warranty. That's simply false.

Anyhow, back to the main subject, what's DrH most likely going to show? I suppose it could confirm that I have high temps - which leads my to the relief valve (or maybe even impeller which i doubt). I really think it's an issue with a bad number getting sent over NMEA2000.

I was able to run today and as the temp crept up to 210 after running for about an hour at 4500rpms/35mpg (and still no alarms) I stopped and pulled the cover off the port engine (while still running in neutral). I didn't have an infrared but was able to touch the engine without burning my hand. Also, the piss stream was far from hot. If it's a bad NMEA number then that would need to be flashed/fixed. But with the not very hot piss stream, that could indicate a problem with the relief valve sticking closed (or is it open!), right? Anyhow, I'd greatly appreciate more advice.

Fair enough on your warranty, it does vary country to country, I am not going there. As far as piss stream is concerned, it should be cold, that water comes from a passage in the mount case before entering the power head and cannot be used in any way to judge engine temp, in fact, if it's warm it often indicates engine is running hot. NMEA data will be exactly the same as Dr H. The difference being that NMEA only reads the block temp when there are 4 temp sensors in all. Dr H will determine which sensor is over reading. Pressure relief valves are an extremely rare problem on these engines despite it being discussed regularly on this forum. Dr H will also tell you how many overheats you have logged. It is possible that it is running that hot if you're in very warm waters, are you? The other question is, are both engines running at the same temp?

Thanks iang. Yes, i run in south Florida. I have noticed that when the water temps decrease during the winter, I'm not running as hot. As they are now back in the low 80s, my engine temps have increased. And the rare alarm that I would get (i think I've had 2) were really long runs with the water closer to 90. Both engines are within a couple degrees, and I've seen a variance of 4 degrees during the long runs. One other thing i didn't mention is when i changed the thermostats, i was impressed with how clean things looks. A little bit of gunk, but nothing like my old days of what i'd see changing an inboard manifold.

I love my 2 hondas, but I miss the old days of having an analog engine temp gauge showing 140! I hate seeing the 200-210 on the NMEA.

One last thing, I'm pretty sure I was told when I bought the boat/engines (new) that it would show different temp (not the usual 140-150). I just don't want to believe it - especially when i see 200-210.

I think my next step is DrH - even i have to buy my own. Thanks for all your help, and stay safe!