Mariner V-150 Overheating

[TACOMATruckin98]

Hi everyone, I do not post much here, but just browse from time to time. I have at the beginning of last summer purchased an 84 Procraft 1750 with an either 83, or 84 Mariner V-150 V-6. The motor ran great all summer until the last time we took it out a few months ago. I do not know any of the maintenance history of the motor, but it looks to have been pretty well maintained. The last time we took it out, the boat was running great, no problems with power at all, but I noticed after warmup and a probably 85% throttle run straight across the lake probably 3/4 mile, we pull up to our fishing spot and there is only steam coming out of the exhaust. Strange, but I thought maybe a wave just hit the exhaust when we stopped because there was no alarm or loss of power. Well we went back to the dock to grab a snack after a while, no problem starting at all. Got back to the dock pulled up, and there was steam again, no alarm at all, no cutback in power, nothing, but when I went to start the motor right back up, it turned over and started, but as soon as the key was hit the very loud alarm went off. Knowing I couldn't blow this motor, I shut it right back off, tilted it up and checked that there was nothing wrapped around pickup and there was nothing. After letting it cool off about ten minutes, I cranked it up checked the tell-tale, which seemed to be perfectly fine, and started slowly back across the lake, just barely on plane and had my buddy on the back deck to watch the exhaust/tell-tale, and I leaned down to make sure no alarm. Seemed fine so I pushed it on up to near WOT, never heard any alarm at all, no power reduction, but started steaming again so we stopped and allowed it to cool about 5 minutes and there was no alarm at that point with the key turn. Tested the compression, 120-123psi across all 6 cyl's, no tell-tale reduction, no overheating at all running at idle for almost 20 minutes. I know that I will replace the impeller before the season, but I need to know if that is my only problem, so I replace everything I need to while I'm in there. Also, the prop looks to be marked as a Turbo M14 1/2 x 2Y? And attached are pictures of the motor height on the transom to try to make sure to rule out everything. Thanks for any help!

 

[nbnewbie]

Re: Mariner V-150 Overheating

You might try checking the lube in the lower unit. Make sure there is no water in the oil. What happened to me with a mercury v6 was it was also overheating similar to what you are describing. I changed the pump impeller got some improvement but still not right. It was near the end of the season and I always change the lower unit oil at the end of each season when I drained the oil there was a very small amount of water in the lower unit my first thought was propeller shaft seals but I pressure tested the lower unit and it was fine upon further inspection I was able the determine that the seal at the bottom of the water pump base was leaking (not much but enough to cause mild overheating) changed the water pump base and gasket and solved my trouble. Water pump impellers get changed quite often but I was not in the habit of changing the base and seal on a regular basis but I do now. just a thought good luck!

 

[aussieflash]

Re: Mariner V-150 Overheating

Check your tstats.

 

[coastalrichard]

Re: Mariner V-150 Overheating

Steam coming from the exhaust can be an indication of water intrusion into one or more cylinders.

 

[TACOMATruckin98]

Re: Mariner V-150 Overheating

Well, it's not as much of steam through the exhaust, as it is steam out of the tell-tale, and rear exhaust that normally would be water. Also would the poppet valve do this problem possibly? I am contemplating just putting new water pump, t-stats, and poppet in, or do you all think this would be more cost than it is worth? I plan to pull the stat's and test in a pot with thermometer. I had also thought that maybe the motor could be too high for picking up water, but this is my first boat with a jackplate so I have no experience in setting the height really.

 

[Faztbullet]

Re: Mariner V-150 Overheating

I nstall a full water pump kit with gaskets,test the t- stats,test the overheat alarm and install a 0-30 psi water pressure gauge.

 

[TACOMATruckin98]

Re: Mariner V-150 Overheating

Ok well, I am also having a problem trying to confirm the correct part numbers, my motor is a serial 6366662, as best I can tell from maxrules I will need their part number 3316 being the full kit, found here http://www.maxrules.com/fixmercwaterpump.html#3316 as well as t-stat kit, part 75692T2 found here http://www.maxrules.com/fixmerctstats.html#75692T2 being as this is a purely freshwater engine. However of the same site, I believe that the correct poppet kit would be part #8031 as my motor is pre-1986. Can someone confirm this, because I would hate to purchase and tear down my engine and be incorrect parts if I do test the t-stats and one or both is bad. Thanks!

 

[oldman570]

Re: Mariner V-150 Overheating

Water pump kits for your motor are listed at Crowley Marine also. They have complete diagrams where you can see just what you will need to replace stats and water pump complete.
Oldman570

 

[CharlieB]

Re: Mariner V-150 Overheating

Steam coming out the 'P' tube is never a good sign. On a V-6 it is often a sign of a leaking head gasket at high engine throttle/load, allowing combustion pressure to leak into the cooling passages, displacing water, over-coming the water pump and the motor rapidly begins to overheat. Sometimes this leak is contained at lower throttle settings and the water pump is then able to cool the motor.

It would be a good idea to pull the heads and closely inspect the heads, gaskets, and cyl block for signs proving the leak. Check the heads for straightness, use new head gaskets and reassemble, torquing the headbolts in the steps and pattern specified in the factory service manual.

 

[TACOMATruckin98]

Re: Mariner V-150 Overheating

Well guys, I finally got the nerve up to put the pump on myself, wasn't too hard, also tested in a boiling pot the t-stats and one failed to open, replaced those pieces and tested on the lake yesterday and seems to be all fixed. I thought that it had a good stream before, until I saw it now after the new water pump. Thanks for all the help