1989 Mariner 150 Magnum 11 alarm issues

[Moser]

Hi guys, my name is Larry and I'm having some issues with this V6 motor that I'm trying to straighten out for a coworker so he can sell the boat/motor combination. By trade I am a toolmaker/CNCmachinist, but I tinker with outboards just because I enjoy messing with them and figuring out what makes them tick and not tick. This is my first Scream and Fly post. If you rate outboard mechanics on a 1 to 10 scale I consider myself about a 5.5. I am a good mechanic, but I have lots to learn. Most of my outboard experience is on OMC twins and triples.

The owner was getting steady alarms off and on, mostly at idle and loading unloading the boat. He put in a new water pump kit but got no telltale running on his muffs, he said "I give up, see if you can get this running and sell the !@#$%^ thing." He started shopping for a new Striper rig.

I put new thermostats in and the motor alarmed intermittently on the muffs in my driveway but had a good telltale, and then didn't alarm at all when I put it in the tank at my friends shop. I let it idle in his tank for about 15 minutes while I helped him with something else and it never made a peep. We ran the rpm up a bit and saw from 5 pounds to 15 pounds of pressure on the water pressure gauge. The telltale was weak until the thermostats opened and we saw water coming out at the exhaust port up below the telltale. We figured it was OK and I took it to the launch for a test run.

It idled out of the no wake for about 15 minutes without a peep then right as I was about to go it alarmed something like this Beeeep......Beeeep......Beep...Beep...Beep...Beep. ..Beep...Beep...about 20 times then BEEEEEEEEEEEEEEEEEEEEEEEEEP STEADY, for about 30 seconds, so we turned back. About the time I turned back it quit beeping so I turned for the open water idled along for about a minute then let her rip. Took about a 5 mile run at from 1/3 throttle to wide open without a peep from the beeper, and with 8 to 15 PSI on the pressure gauge every time I looked at it. A we approached the no-wake on the way in and it was coming down off of plane I got about 4 or 5 interupted beeps and then it was quiet all the way back to the dock. The guy with me said he noticed when it was alarming it let out a little puff of smoke. I did not notice the water PSI while the alarm was sounding, my bad.

Can someone who understands this cooling system, warning system and the oil injection system and the relationship between the three help me try to understand what's going on here. I called the owner and he said "Yep, It always did that ever since we had it, we just ran it. If it's peeing and not alarming at idle you fixed it." That may work for him OK and it may be just fine to run, but I can't sell it like this. If it was an OMC I'd be thinking about jerking the tank out, unplumbing the oil pump, disabling the oil side of the alarm and pre-mixing the gas about right now.

I found this forum doing searches on this but don't see the alarm explanation I think I need. Any help is deeply appreciated.

[CharlieB53]

Inspect the water pump housings for warp. A warp in either housing can fail to seal and reduce pump capacity. When on plane the water column is gone, the water pump can be exposed to air, further reducing pumping capacity.

Ensure the water transfer tube fit into the 'cushion' seal in the top of the pump, and the grommet seals well at the top of the transfer tube. With the lower removed you can attach a water hose to the transfer tube, turn on the water and easily see if the upper grommet seals, watch your pressure gauge, you can see where the poppet valve opens.

Cyl leak down test, may indicate a leaking head gasket. Symptoms of a heat gasket leak are overheating and/or steam coming from 'P' tube. Combustion gases over-pressure cooling pressure, displace water, reduce cooling. Lower RPM pressure leak contained and full water flow.

Rapid beeping is not a cooling alarm, it is a possible oil alarm. The oil alarm module compares the signal from the oil pump rotation sensor with the ignition pulse (usually cyl #4), when difference is seen the rapid beeping alarm sounds. It is possible the motor has an intermittent mis-fire on acceleration causing the rapid beeping.

[Moser]

Ok Charlie thanks for the reply, I have a couple of questions on your advise. Can I do the cylinder leak down with my regular compression tester? I'm assuming I can turn it in a little farther and get a good seal around the plug hole then crank the motor over until it goes through a couple revs then hold the release button in and watch for bleed off, right? Should it hold indefinetly, or is eventual bleed off OK?

I think I understand everything to check on the lower as far as the pump housing, seals and so forth. I'll pull the lower and check that all out before I run it again. If it means anything to you the owner said there was a beed of RTV silicone along the front of the pump housing when he pulled it off that he did not put it back. He replaced the entire pump assembly, not just the impeller. I told him I was pretty sure that it was designed to work without any silicone in there and I would not put any back. I guess I have to get that offf and get a look at it. I'll try to post up a picture if I find anything unusual. I changed the impeller and housing more than once on a 1996 90 ELPTO I used to have so it isn't a complete mystery to me.

One thing about this beeper is that it does not sound for the self test when the ignition is turned on, but does sound for a few seconds when you first crank the motor. It does not sound after the first cranking cycle. I got both the interupted rapid beeping for an oil alarm which turned into the long steady beep for overheating after an extended smooth idle period out through the no wake area. When the beeping stopped we decided to go ahead and the engine sounded no alarms until we came back down off of plane at the end of a 10 minute ride. It then beeped rapidly about 4 or 5 times and was quiet all the way back through the no-wake and through the loading process.

I am going to mix enough oil into the gas in the tank to bring it up to 50-1 before I run the motor again.

Thanks for the reply, I really appreciate having some guidance here

[Wayne Cammidge]

Hi Larry.

Looks like you could have a few different issues going on at the same time.
When the water pump was replaced, did they replace the lower housing as well, it does not come in the water pump repair kit. Most times that the upper housing is damaged hectically badly, the lower housing should also be replaced. But I also do not think that you have a water pump issue, just re-check the pressure coming off the plane.

With your 50:1 oil mix in the boat tank, disconnect the wire that goes to the alarm from the oil warning module, and try it with out the oil warning connected. That oil warning module sounds very suspect.

If you still get intermittent peeping, then you could have an issue in the wiring loom running to the horn

[Moser]

Thanks for your reply also Wayne, I'll try that with the module unhooked, and I'll find out about the lower housing. I still think I'll drop the lower unit and take a quick look at everything.

I did see something on another post about a beed of silicone seperating the pump housing from an exhaust chamber. I'll see if that makes any sense when I get the lower unit off. Does that ring a bell with anyone?

BTW you'll see a lot of late night posts from me, I work 4-12 and I'm just going to bed. :)

[Wayne Cammidge]

When the motor comes new from the factory, there is a bead of silicone. I do not disturb what is there when I strip it, but put it back together as it was with no further silicone added. Never had any issues.

[sleekcraft sst]

Had oil alarm doing odd things once like that just before the oil drive gear failed . Remove oil injection and premix. Then you will never have oil alarm again then you'll only have over heat alarm to worry about . Cheaper then a oil control modular replacement or power head .

[Moser]

I know he won't want to put any money into it now that he's looking at another boat, so pulling the injection stuff might be the best fix. We have a second co-worker involved now who says he'll buy it if we get the alarm issues straightend out. My plan is to make sure the water pump is all together right, put the bead of silicone back and make sure the lower unit is back on correctly, do the bleed down test to check for weak head gasket. I'm also going to pull the oil pump off and inspect it for damage or signs of pending failure, check all the hoses, caps and sensors on and in both tanks. When all that is done we'll pull the power from the oil module, pre-mix the gas 50-1, run the boat and see if it alarms. If it doesn't we'll hook the module back up and test it. If it alarms then then we'll lay the options on the oil alarm out for them and let them decide if someone wants to lay out $200 for the module. If anyone sees something I've missed please sound off. Thanks much guys, I'll post back what I find and how it turns out.

[CharlieB53]

A cyl leak down is a measurement of air leakage from the cyl, past the rings or possibly past the hed gasket into the cooling system.

My compression tester has a quick disconnect chuck just like many air hoses. The sparkplug threaded end has a schrader valve, like a standard tire air valve which limits air flow to one direction only. I must remove this valve when using this hose for cyl leak down testing.

You must have an air supply to the cyl.

With a compressed air source I use a regulator set to 100 psi feeding a second pressure gauge that once chucked to the cyl (piston set exactly TDC) will show what pressure is holding in the cyl. I then can listen carefully around the motor to gauge where any leakage is.

The piston MUST BE exactly TDC or the applied air pressure push the piston down and will roll the crank. Holding with a wrench can be dangerous as the crank can turn with sudden force.

Leak down testers can be found at many auto parts stores , tool stores/outlets, on-line sales. I built mine very easily and cheaply. Why pay the Snap-On man another hun or more, I had the reg and gauges laying around the shop, just needed a couple of fittings to screw them together.

[Moser]

OK I think I have it on the leak down test and I can do that with my tester.

I found out today that this boat has been like this for YEARS!! The current owner told me the previous owner told him he always got "false alarms" from the oil warning beeper and if he didn't want to listen to them he should just unhook the injector and mix the gas. That is his proposed fix for us right now, unhook the injector, warning module, pull the tanks and mix the gas. I don't like to pull a good pump off the boat if the module is the only problem, but this fellow has moved on from this boat and just wants it sold ASAP, without putting anything more into it than he has to. I'm not going to argue with him.

I guess removing the oil injection would go something like this:

Mix the gas in the tank with enough oil to bring it to 50-1, run it long enough to insure that gas is all the way to the carb.

Pull the tanks out of the boat and off of the motor.

Unhook the warning module.

Replace the hose from fuel pump to carb, or plug the hose in the T coming from the injector pump.

Can the injector pump just stay in place or does it need to come off?

I really don't think we have a cooling issue, but an oil injector module problem. Unhooking the injector and removing the alarm module will fix that I think.

I will run the boat after the leak down test and lower inspection with the module unhooked, 50 to 1 mxed gas and the injection still in place to see if I get an overheat alarm.

Thanks for all the replies, you got me headed in the right direction.

[Moser]

Do the sending units in the heads both do the same thing? The port side sending unit is just hanging there unhooked. It has a plug on the end of the wire not a round terminal like the other side.

I had an hour to mess with this yesterday so I unhooked the purple wire bringing power to the module and the brown wire that I'm pretty sure lets the alarm signal from the module go to ground. I left the s'board temp sensor hooked to the insulated post on the block where there is a hot wire and the brown going to the temp sensor.

I think this takes the injection sensor out of the picture. I'm going to add some oil to the 10 gallons of fuel in the tank and leave the injector alone. I'll tell potential buyers what is going on and give them the option of having me unhook the injection or put on a module, or (I hope) they can take it to a different mechanic.

I'm going to do the leak down test and double check the lower unit still, but now I can let people try the boat without the oil warning beeper going off.

[Wayne Cammidge]

Some models have 2 different heat sensors. The one with the bullet connector usually goes to a temp gauge on the dash. Some times that sensor also has wiring which goes to the alarm