Mercruiser w/ Ford 351w timing / runability / issue

lornemilz

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Joined
Jul 20, 2012
Messages
26
Re: Mercruiser w/ Ford 351w timing / runability / issue

So here is the end all update .

I replaced the distributor with a good used working part. The motor cranked right up and idled smooth. I set the timing on it 10* btdc. The engine has throttle response up to 6000rpm in neutral.

I towed it to my local boat shop and payed for the dyno hook up on it. According to his numbers I should have around 2600-3100 psi of thrust on the machine. Wide open at about 4000 rpm we were sitting at around 2000psi. So basically running at 66% according to his dyno. This isnt too far from what I expected to see being that my compression numbers are lower than they should be and cylinder 6 still has issues. He showed me my impeller in the outdrive needed to be replaced so I bought one and swapped it out. The engine runs at an acceptable temperature. It doesnt stall or backfire. It doesnt leak anymore. I also replaced the prop with a decent used prop as mine had spun the inside rubber.

He said I would be lucky to see 10mph on the lake with the dyno results. Im not so sure I 100% believe that but I take it for what its worth. My first outing on the boat it ran about 2000 - 2800rpm on the lake, roughly 30mph. It was sluggish getting there but it did get there. I plan to do a lake test to see the results first hand before going any further. The cost of the reman long block is more than I want to add to this boat at this time so it might go up for sale as is with the bad cylinder.

I appreciate all the help and feedback.
 

lornemilz

Cadet
Joined
Jul 20, 2012
Messages
26
Re: Mercruiser w/ Ford 351w timing / runability / issue

Lake test results so far as follows.

Timing was set way out at 14* BTDC. Air / Fuel screws out 3 turns. Motor is still less than impressive on acceleration but does reach around 3200 rpm and roughly 28mph. I will adjust points and timing once again this weekend to try and get it to a more acceptable position.
 

joewithaboat

Lieutenant Junior Grade
Joined
Jul 3, 2011
Messages
1,172
Re: Mercruiser w/ Ford 351w timing / runability / issue

Are you sure the prop is not too big? Maybe someone kept a prop they wanted and stuck whatever they could find on it to sell it to you.
 

haulnazz15

Captain
Joined
Mar 9, 2009
Messages
3,720
Re: Mercruiser w/ Ford 351w timing / runability / issue

I don't recall what we were working on carb-wise, but the air/fuel screws are normally just for idle. They don't affect the main circuit.
 

lornemilz

Cadet
Joined
Jul 20, 2012
Messages
26
Re: Mercruiser w/ Ford 351w timing / runability / issue

Are you sure the prop is not too big? Maybe someone kept a prop they wanted and stuck whatever they could find on it to sell it to you.

The prop I have on there is a used one from a local boat shop. I believe its a 19 or 21 pitch. I would have to look again. From what I understand the lower the pitch the better the holeshot.

I don't recall what we were working on carb-wise, but the air/fuel screws are normally just for idle. They don't affect the main circuit.

In my line of work carbs typically start 1.5 out and mainly affect the air / fuel at idle to 3000 rpm. But the motors I deal with rev to 9000+. I could still see it affecting it beyond 1000rpm.

Todays trip yielded other results. I tried to adjust the shift cable on the lake and got all *** backwards; ended up manually putting it in drive for most of the day. Then I snapped my serpentine belt in half and that was the end of the day. I didnt get a chance to adjust points or timing any further. This week I need to get the shift cable figured out before I can get back out there.
 
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