MULTIPLE MOTOR ISSUES?

RussRuss

I have a 2005 270 FV with a 350 MPI, upgraded to a 6.2 with a Mercruiser repower long block with less than 100 hrs on it now.  I have a few separate issues and would like any advice before I really dig in:

1 - "Minor" knock/ratlle/??? in motor or outdrive.  Not detectable at startup, but comes on as it heats up.  I tried a stethescope and had several knowledgeable folks listen but not clear to anyone if it is a rattle, knock in motor, or an outdrive noise coming in through drive.  Unless someone has a better idea, I plan to pull it out of the water, pull the drive, and see if the noise is still there.  If still there open up the motor and look for the problem.  The only other suggestion I had was to do a compression check, but I am not sure what that would do other than give me a sore back.

2 - Even when the knock is there, it idles around like a champ.  But when I power up to get on plane, I get a serious hickup and then it immediately jumps back to full power, and then hickups again, etc.  I am guessing a loose connection, because it is a total drop in engine power and the tach pegs to 0 like it lost power.  I am putting in a new needed battery and will start checking every connection from there unless there is some other good idea of a strategy to find it.  The only other thought is isn't there a knock sensor of some sort on these motors?  Would it behave like this and if so, can I temporarily bypass it to see if that is the issue?

3 - When I turn the key, sometimes nothing happens.  The fuel pump always spins up but the starter doesn't always engage.  I turn it a few times and eventually it kicks in.  Does not matter whether I am on battery 1 or 2.  Maybe my loose connection between batteries and starter, but could that give me the power up hickups when it is already running?

Thanks for any advice!

212rowboat

man, a bad connection at the batt could be all of those things.. the knock being the jump.. certainly for everything other than the knock it can be power related..

as far as the knock goes, and since it is a new rebuild- I would first guess hydraulic lifters leaking... once you've heard one you won't mistake it again.. it is a pronounced tapping sound..

they usually get to the point to where they won't charge at all because the spring gets worn and won't return- but until then they either don't charge up at idle or they won't charge up at speed... there is really no damage that can be done, unless the engine is an inference engine (the piston can smack an open valve if the mechanical timing is wrong)... I don't think these are inference engines, but I may be wrong.

Black_Diamond

#3 - could be a neutral switch, does moving the shifter make a difference?  Could be the solenoid at the top of your engine, by the red circuit breaker too, they are known to be issues.

Dream_Inn

I'm with BD on #3.  First thing I thought of...been there done that. L-)

I've also seen cleaning battery terminals real well help many items.  Those two are where I would start.

aero3113

Could the knocking be your exhaust flappers? You will hear them at idle bouncing around then they fully open at power.

RussRuss

Thanks to all for the feedback - I will check those ideas out.

Black diamond, can you be more specific about the location of the solonoids you mentioned?

I remembered I have a video with sound of a mechanical oilpressure gage I hooked up. Sounds more like a knock on the video than in person, but maybe it is what I don't want to hear :-( The oil pressure also jumps around some is that normal? Is it possible to post video on this site?

Black_Diamond

Should be behind your throttle body. The circuit breaker has a big red button on it. The solonoid is right with it.

Lifes Good

Concerning your power loss. I had a simular gremlin back in 09. After many frustrating hours of checking every wire on the boat for the voltage drop which killed the engine for just a second randomly at any rpm, It turned out the red battery cable to the starter was loose enough to lose contact. Give the bolt on the starter a good turn to be sure its tight.