Engine Mount Adjustment

[Mark A. J.]

I am a new boat owner and haven’t found an answer to this question elsewhere yet. I have a 2007 Maxum 1800 ST3 with Mercruiser 4.3 MPI and Mercruiser drive. I noticed that port front engine mount was loose. So loose that I don’t know if the top nut was even touching. I tightened it down and then noticed that it was much lower (3/4” maybe) than the front starboard mount.

It had had some power steering fluid leaked on it so was very lubricated. I thought maybe that the bottom nut may have vibrated down with vibration, weight, and lubrication. I pried it up a bit and spun the bottom but up maybe 1/4” inch. It still sits lower, but now I’m second guessing moving it at all.

Im not even sure how the engine driveshaft aligns to the drive. Is this a precision fit? Should I put it back down roughly to where it was, bring it up in line with the other side, or check alignment somehow?

I was was thinking that since I was able to pry it up, that it was likely an indication that it wasn’t being properly supported at that corner. If there were an alignment problem, would I be able to identify that by vibration if I fired it up now and engaged the drive?

Thanks!

 

[tpenfield]

Well, the proper way would be to not adjust the engine mounts UNTIL you had the outdrive off and were using the alignment tool to check to see if the engine mounting is high/low or correct.

Since you adjusted the engine mount, you should probably remove the outdrive and check/adjust the alignment per the standard procedure. Otherwise, you run the risk of ruining the coupler at the rear of the engine.

 

[Rick Stephens]

Agree with tpenfield. If you are going to do your own maintenance, then removing the outdrive will be at minimum an annual inspection and maintenance item. Only take 10 minutes or so. You will probably need a new bell housing gasket.

When front engine mounts are not equal in height, to get them even, it is easiest to suspend the engine from its front alignment loop, that is attached to the thermostat housing usually and made just for that purpose. With the motor mount nuts loose, lift the front of motor a little off both sides lower nuts, then adjust lower nuts until they are the equally able to take weight. The motor, when suspended by the front like that will be held in place by the two rear mounts and sitting level. That gives you a starting place for the front mounts that is level. Then use an alignment bar to go through the alignment process while keeping the front mounts level to each other - one turn on port and one turn on starboard..

 

[Mark A. J.]

Okay thanks guys! You put me on the right track here. I’ve ordered the alignment tool. Only 85 hours on this engine, but not knowing the history, with one front mount completely loose and the two front mounts being so uneven, I think it’s best to check the alignment.

To be clear though, I shouldn’t have to worry about rear mounts? I should just be able to hang the engine from that middle loop and if the front mount points are uneven, then that’s nothing to be concerned with?

 

[Rick Stephens]

If that is a 12 year old boat with its original 85 hour motor, then it was a typical BADLY abused motor. Hardest thing on a boat motor is putting a few hours a year on it and parking it all the time. Worse yet, putting fifty hours on it first year, then a few the next and parking it for near a decade. That said, motor hours don't mean anything here. Boat condition, stringer and transom wood condition. Everything adjusted right. And proper maintenance moving forward is what keeps a boat from being more expense than they're worth.

Most likely the rear mounts are fine. You can look and make sure they are even. Use a camera on your phone to get a better look if you can't get your head in there. Don't hang your motor off the loop until the you have removed the drive.