boatinbill

I have posted this question in the general forum and Tech Q&A sections, so if you see it else where, no need to answer.

I have a question for all you motor heads out there. I ran the boat for the first time last week end. Started fine, no noise, plenty of oil pressure, everything fine. I ran for about 2-3 hours and had to out run a thunderstorm to a marina. When I got in out of the rain, I checked things out and found oil in the bilge. Checked and I was a little low, looked like it came out the dip stick tube(?). Added some oil (took about a quart to top off) and started the motor and I had a low energy knock coming from the top and back of the motor. I idled it home and put it on the trailer. Got this feedback from the mechanic today.

Originally thought it was a fuel injector, nope.

Now, after talking to Mercury High Peformance, he thinks it is a roller follower on the cam, may need new cam shafts and roller rockers and exhaust valve springs. He says oil in the bilge was from a front seal leak on the drive (not there last fall when winterized).

He said that this cam/rocker/valve spring problem is not unusual for the 1998-1999 HP500's with approximately 150 hours on them. Mine is a 1999 with 175 hours on it.

Anyone else have this problem?

mopower

A friend of mine is a Mercruiser mechanic , and yes , those HP 500's were noted for valve spring problems at about 150 hrs. Merc has since switched to a different spring. Good luck!

boatinbill

Here's the latest.

Mechanic can not find any visible signs of damage in the upper end. He talked to Merc HP and Bob Teague, both have said no problem with valve springs on the HP500EFI, it was a problem with the HP500 carberated engines.

Cams look fine, replacing lifters should have the boat back by next weekend, will update after I run it.

Thanks for all the input and advise

boatinbill

Lastest update, knocking returned very quickly (matter of minutes on the water), mechanic took a compression check and found number 7 cylinder down to 40lbs. Pulled the head and found the number 7 piston burned.

Knocking now expected to have been carbon hitting the head.

No final cost yet, but expect it to be steep, and I have lost half my summer.

Hopefully it will be fixed (correctly this time) by this weekend.

Mama tryed (32 Sunsation), Kenny (aka Wheeler Dealer)(27 Fountain) and AeroBob (31 Aerotech) thanks for all the rides in the last 6 weeks, with any luck I won't need them any more. Nor will I need to take the old pontoon out any more.

There are many questions as to why this was not found earlier, but live and learn. Probably the best question now is, where is there a good mechanic in the St. Louis area?

For what it is worth, I have now also been told (second hand) that several HP500's have had the number 7 piston go south in our area lately.

jrocket

Feel for ya bud!! Lost my motor on mothers day itll be wett this week though 502mag... Salvaged crank, block, rods and heads. $5 Gs later...... But dammit she should have some serious flow now. Make the best out of it UPGRADE!!!
by the way It was my cam! lost a few lobes.