Ran boat into very shallow water!

[MH9371B]

Had my boat out Sunday and I was cruising along at about 25mph when I ventured out of the channel just a TINY bit and WHAM, everything came to a halt. Got boat off sand bar and for the rest of the trip home, lower unit would not trim all the way down. When I got back to the ramp, I was missing some paint obviously, but after getting the boat on the trailer I was then able to trim the engine all the way down.<br /><br />Is there something I should be looking for?<br /><br />1995 Mercruiser 3.0LX 135HP w/Alpha 1 gen 2

 

[Luna Sea]

Re: Ran boat into very shallow water!

You mean besides sandbars?<br /><br />Sorry, couldn't resist.

 

[RatFish]

Re: Ran boat into very shallow water!

I did the same thing in spring. Ran fine all summer.

 

[MH9371B]

Re: Ran boat into very shallow water!

Luna:<br /><br />Low blow!<br /><br />But very funny!!<br /><br />Rat:<br /><br />Did you have problems trimming all the way down right after it happened?

 

[tommays]

Re: Ran boat into very shallow water!

i have done it more times then i would like to admit and the main problem tends to be what the water pump sucked up and if the impeller was damaged<br /> <br />i dont no how old you pump is for right now keep a carefull eye on your engine temp for any signs of overheat<br /><br />the second thing is that on a hard hit you may losen the transom assembly and get a water leak mine has not gotten lose but it is possable for it to start leaking<br /><br />tommays

 

[RatFish]

Re: Ran boat into very shallow water!

Nope. No trim problems. The only damage/problem was the missing paint on the skeg and my pride.

 

[MH9371B]

Re: Ran boat into very shallow water!

Water pump is actually brand new as is impeller. Boat was showing some signs of overheating but I assumed that was because my lower unit was trimmed way up and stuck on that position on the way back in. I figured it was not getting sufficient water flow? Engine kept reasonably cool but still not as cool as it should have been.<br /><br />Tommy: when you say a water leak, where would I notice that. In the bilge?

 

[Luna Sea]

Re: Ran boat into very shallow water!

MH, Glad you took that as intended, humorous.<br /><br />Never had an outdrive so can't offer help.<br /><br />But have dealt with enough mechanical gizmos to know after an impact, things don't sometimes work right, for a while. Maybe the fluid got tossed about enough to have an effect, maybe something heated up, ect. Just keep an eye on it.....<br /><br />And good luck

 

[tommays]

Re: Ran boat into very shallow water!

in the inside stern of the boat were everything bolts to the transom with a 3.0 you should have a good view its should be ok but keep and eye out next time you launch<br /><br />you may have to flush out the motor to get all the sand bar out i have had stuff hangup on the t-stat and block flow or even kep it from closeing on my 3.0<br /><br /> <br /><br />tommays

 

[Bondo]

Re: Ran boat into very shallow water!

Water pump is actually brand new as is impeller.

That was Before you pumped Sand through it.....

 

[achris]

Re: Ran boat into very shallow water!

Inside the trim rams are 'memory' pistons as well as the pistons on the end of the shaft. When you hit something (a sandbar in your case) the main pistons vent fluid so the drive can kick up. They also have a relief to allow that fluid to return to the 'upstream' side of the main piston after you come off the obstruction, but it needs a bit of force to open the relief, namely you running the engine with a bit of throttle on. I am guessing you didn't run more than idle for the trip back to the ramp. The main piston (and ram shaft) will return to the position of the 'memory' piston, which 'floats' and isn't attached to any shaft. The other way of 'resetting' it all is to tilt the drive all the way up and then down again.<br /><br />Chris..............

 

[rodbolt]

Re: Ran boat into very shallow water!

hello<br /> Ill second bondo and achris.<br /> it was a new one<br />may not be so new now.<br /> achris is right on about the memory piston. sometimes the drive has to be cycled some to reset the memory piston.

 

[MH9371B]

Re: Ran boat into very shallow water!

achris:<br /><br />Thanks for that insight. I wasn't aware of that feature at all. I have successfully cycled the trim all the way up and down numerous times given my curiosity to if it even worked anymore. <br /><br />Of course thanks Bondo for yet another sarcastic, yet functional reply!

 

[KaGee]

Re: Ran boat into very shallow water!

Wish MY memory could reset as easy.

 

[Don S]

Re: Ran boat into very shallow water!

Achris had me doing some checking for a while because I have never heard of a "Memory piston" in the drive. And after checking, I still have never heard of this. There is a shock piston, and sometimes a spacer piston to prevent the trim from going up too far, but nothing about a "memory piston" in the service manual.<br />Here is the section of the service manual dealing with the trim cylinders.<br /> Section 5B Service manual 14 <br /><br />We have had boats come in with similar problems and the check valves in the trim pump were stuck closed due to the impact and usually after a few tries running the trim up and down they freed up and worked fine.

 

[Fishermark]

Re: Ran boat into very shallow water!

For what it is worth, (probably not much ), I have done a lot of boating in Tampa Bay and here in Charlotte Harbor. It is almost impossible to avoid the shifting sandbars - even in the marked channels. (I put in at Cockroach Bay quite a bit - just North of Port Manatee - lovely name isn't it? - it is not uncommon to hit ground in the marked channel). I've never had any problems with damage to the lower unit nor the impeller with the sand that is picked up. Mind you, I haven't been going fast, but I know quite a bit of sand is always churned up.

 

[achris]

Re: Ran boat into very shallow water!

Don,<br /><br />In that PDF it's called a floating piston. I have the Merc training notebooks and it's called a 'memory piston' in those.<br /><br />Chris......................

 

[POINTER94]

Re: Ran boat into very shallow water!

Pulled the same number on castle rock lake about 6 weeks ago. I was going about 12-15mph and hit a muck/sand bar. Not a hard hit but it brought me to a complete stop. <br /><br />I checked the lower unit oil to make sure that nothing was creating a water leak and then I changed the impeller. Maybe alittle bit of an over-reaction but half the fun is working on a boat. I have found and I am sure there are others that know better that an impeller that has lost it seal will show up at idle with the temp creaping up. Goosing the engine brings it back down.<br /><br />All was well on my end but I haven't pulled that number in many years.. Nope, I didn't like it. This feels strangely like confession..

 

[rodbolt]

Re: Ran boat into very shallow water!

hello <br />the memory piston,shockpiston or free floating piston,depending on what manual you have, is a device that in theory wnen the drive hits a solid object allows fluid to pass through the valving in the piston to allow the trim rods to extend and then the rods can move back to the position they were in before impact. sometimes the fluid wont flow back and the drive must be cycled once or twice to set the memory piston back against the ram. its common<br /> good luck and keep posting

 

[MH9371B]

Re: Ran boat into very shallow water!

I've checked impeller, it looks fine. The sand was extremely fine where I hit ground and after heading back to the ramp in idle speed for 2 hours, and 30 minutes of flushing from home, everything seems to be OK.<br /><br />I'm going to put her in the water today and see what happens! Deep water, obviously...