150 V-6 High temp alarm at high RPMs

[bdallam]

Hi folks, I'm new here. I just bought a used 150 Black Max, (1986?) from a performance shop and hung it on the back of a used Wellcraft V-20. It had to go back right away for an oil pump and drive gear, now after getting it on the lake for the first time I get the High temp continuous alarm tone as soon as I open it up when the rpms hit 4000-4500. If I shut it right down as I've been doing, and restart it immediately I can run it up to 2,500 with no alarm. In fact, it appears it will run at 2,500 for quite a while without the alarm coming on. I tried 3,000 and got the alarm after about 5 minutes. Seems to have a good stream pissing out the telltale. I talked to the guy I bought it from and he's said to bring it back down. He was talking about the alarm module being bad? Sound reasonable? Unfortunately this thing has no temp or water pressure guage, (although I've ordered both). I wish I had a better idea of what was going on before I drive it back down to the shop as I go back and forth about trusting the guy. BD

 

[bdallam]

Re: 150 V-6 High temp alarm at high RPMs

After a little searching on the engine and the internet, I believe it's a 1987. BD

 

[garyj]

Re: 150 V-6 High temp alarm at high RPMs

BD,<br /> It could be a stuck "poppet valve". This is the pressure relief valve located at the bottom of the powerhead on the starboard side. If it is stuck in the closed position, it will not dump enough water at higher rpm's. Look at the rectangle exhaust ports and see if it is dumping water at mid to high rpms. Also, if you just installed this motor on the boat, check to see if the motor is low enough on the transom. May be picking up air..<br />Just my 2 cents...<br /><br />Southern Catfisher

 

[achris]

Re: 150 V-6 High temp alarm at high RPMs

Hey Gary,<br /><br />Did you get your heating/hot cylinder problem sorted?<br /><br />Chris...........

 

[bdallam]

Re: 150 V-6 High temp alarm at high RPMs

Thanks for the response. The anti cav plate is about 1/2" above the keel. I do see some minor water spraying out of the square exhaust ports, but no real volume. I guess I'd have to remove the prop and rev it up at the dock to really check on that. Seems like it would be risky business to try and get a good look at those ports underway. BD

 

[garyj]

Re: 150 V-6 High temp alarm at high RPMs

BD,<br /> Yep, risky business is right!! Not a good idea to be checking out the motor at 60+ mph. Have someone take a look for you. Have you checked the water pump? If its not dumping a lot of water out the exhaust ports, maybe the water pump isn't keeping enough pressure to open the poppet. Checking the pump impeller would be the first thing on my agenda.<br />The alarm thing. I would assume that it is working properly unless disproved with the heat gauge. Don't let the guy disable the alarm...<br /><br />Hey Chris,<br /> I'm stilllllllll working on the motor. After finding the dry cylinder, I broke down and took it to the stealership. After much debate, the diagnosis was that ALL cylinders should be dry. There is no bleed hose connected to the #3 cylinder, therefore excess fuel is not redirected to this cylinder. A mercury master tech says that now, they block all the bleed hoses (using a bb) so that no excess fuel is routed to any cylinder. This is what they have done. Now all cylinders are dry. Also, to check the overheating problem, they have went through the carbs looking for a lean condition, checked the timing and all switch boxes, etc.. Did not find anything. Checked the water pump and installed restrictors in place of the thermostats. It's still running hot at high rpms. They were supposed to install a water pressure gauge. Didn't happen..back order. (It tough to live in a small town). The gauge should be in next week. Hopefully this will let me know where to look next. The tech says that not enough pressure would indicate air intrusion into the cooling system, or pump or gasket problems. A higher than normal pressure would indicate an obstruction in a water passage. I'm thinking the latter. Since I have had the heads and exhaust plates off, the most likely place would be the adapter plate between the powerhead and the lower unit.<br />If the money holds out , maybe I will find the problem.<br /><br />Southern Catfisher

 

[phatmanmike]

Re: 150 V-6 High temp alarm at high RPMs

hello, im not sure if this will help, but i had very , extremely similar problem with my 1976 115 tower or power. would overheat at high rpms, but operate fine at idle. turns out i had a handfull size of sand and shells and sut in my water jacket, just where the water enters the motor, that would impede the water flow at high rpm's but still flow enough at lower rpm's. just a thought<br /><br />m ikey

 

[KCLOST]

Re: 150 V-6 High temp alarm at high RPMs

Good post, <br /><br />I agree, <br />Check, water pump, poppet, water jacket cover on the heads...<br /><br />Let us know..

 

[bdallam]

Re: 150 V-6 High temp alarm at high RPMs

Ok, the shop I bought the engine from has had the heads off so I'm assuming, (yeah right), that there's not a handful of sand in them. Also, I'm in northern Maine where sand is scarce, and coral is unheard of. The water pressure/poppet valve seems likely. Why doesn't anyone stock temp guages? There's three good size marinas on Moosehead Lake and two other outboard shops, but none of them stock a temp guage. I agree leaning over the stern while under way is a bad idea, but it's not likely that it would happen at 60 mph with this rig, unless I was being towed by an airplane. BD

 

[KCLOST]

Re: 150 V-6 High temp alarm at high RPMs

13536A 7 <br /><br />That's the temp sender you need...<br /><br />79 - 15166A 1<br /><br />That's the guage to go with it...

 

[bdallam]

Re: 150 V-6 High temp alarm at high RPMs

Thanks for the replies. Turns out the shop inadvertently put the wrong exhaust plate back in when they put the powerhead on after replacing the oil pump drive gear. Much egg on their faces, no charge to me, but a 150 mile round trip to sort it out. BD