Not reaching WOT

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armyofdux

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I have a tank of a 1985 Wellcraft 3200 Sport (32ft). Has the original 7.4Ls 454 Mercruisers installed with about 1500 hours a piece. I am the new owner of it. I found the old manuals and made them into PDFs both for the engines and the boat. The book says 4400 RPM is WOT on this model. The most I can muster is 3200 RPMs on a flat calm day, throttle levers buried at about 22-23 knots. I have attached the original spec sheets.

Engine Serial#s A344791 A394876
She will get to WOT all day long at the dock. Any ideas?
 

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beermak

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Re: Not reaching WOT

hi, my sugestion is to check the ratio of the drive, then both propellers to see if they are adecuate. When i got mine, didnt get WOT for 2 reasons a huge pitch prop and a unsealed drive. Both things made it.

Check props, ratios and any water on drives..

U shouldnt rev it to WOT on neutral.. if u did so
 
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armyofdux

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Re: Not reaching WOT

beermak said:
hi, my sugestion is to check the ratio of the drive, then both propellers to see if they are adecuate. When i got mine, didnt get WOT for 2 reasons a huge pitch prop and a unsealed drive. Both things made it.

Check props, ratios and any water on drives..

U shouldnt rev it to WOT on neutral.. if u did so
Click to expand...

I have the two sets of the original props. It is straight inboard, no outdrives. I never reached WOT completely at the dock but you can tell it would certainly get there.
 
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armyofdux

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Re: Not reaching WOT

I can eliminate some of them off of that list right off the bat but I will check again. Is it possible that one of those ailments would prevent the other engine from reaching it?
 
Bondo

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Re: Not reaching WOT

armyofdux said:
I can eliminate some of them off of that list right off the bat but I will check again. Is it possible that one of those ailments would prevent the other engine from reaching it?
Click to expand...

Ayuh,... Several, such as unwanted marine hitch-hikers,...
 
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armyofdux

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Re: Not reaching WOT

Bond-o said:
Ayuh,... Several, such as unwanted marine hitch-hikers,...
Click to expand...

I checked thoroughly...a little bit of slime but as soon as I run the boat it comes off. She was just bottom painted two months ago.
 
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armyofdux

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Re: Not reaching WOT

Well I did discover two things: Trim tabs and spark plugs. That my trim tabs will not go all the way down. The culprit being an extremely low trim tab fluid reservoir courtesy of the moron who replaced my trim tab cylinders after one exploded. So it makes me wonder if I had been running her butt in the water a little and not being up on plane fully.

I also discovered splitfires in all 16 cylinders...ugggh moronic. Who would use those in a boat? Replaced all 16 with AC Delco MR43Ts.
 
achris

achris

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Re: Not reaching WOT

As there is 1500 hours on the engines I would start from the very basics. Compression check, timing and advance curve checks, is the carb opening fully, are all the fuel filters clean?

Once you know the engine's doing the right thing, then start looking for externals...

Chris.....
 
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armyofdux

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Re: Not reaching WOT

achris said:
As there is 1500 hours on the engines I would start from the very basics. Compression check, timing and advance curve checks, is the carb opening fully, are all the fuel filters clean?

Once you know the engine's doing the right thing, then start looking for externals...

Chris.....
Click to expand...

achris... here is a brief update. All plugs were changed to AC Delco MR43Ts and the trim tab reservoir was filled properly. A very negligble difference. The carbs are opening fully and the fuel filters are brand new. I know how to time a car engine but what is an advance curve check? Possible that both engines be out of whack?
 
achris

achris

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Re: Not reaching WOT

What about the cylinder compressions?

'Advance curve' is the curve of the timing against the engine speed... Look like this...

attachment.php
 

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armyofdux

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Re: Not reaching WOT

achris said:
What about the cylinder compressions?

'Advance curve' is the curve of the timing against the engine speed... Look like this...

attachment.php
Click to expand...

Yanking 16 plugs isnt in the timeframe of capability till the weekend. Does timing get out of whack over time? It just seems weird to be 1000 off from WOT
 
achris

achris

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Re: Not reaching WOT

Generally the timing shouldn't change, but that doesn't mean that's nothing changing it. I had an engine (V6) that had a ground problem between the engine block and the distributor, and that changed the advance curve enough to knock 600rpm off the top end....

But until you prove the basics are good and solid, you could be chasing you tail on this one. The only way to find it as quickly as possible, (and with the least expense involved) is to go step-by-step through the proper troubleshooting method.... It's as much about proving what is NOT causing the problem as finding what is....

Chris.....
 
achris

achris

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Re: Not reaching WOT

Hmmm. Just saw something that tweaked by interest... "plugs were changes.." Check the firing order. If the engines are both the same rotation, then if the person who changed them got them both wrong, the same way, there's your explanation... But check the firing order really carefully. Follow the wires from the dissy cap all the way to the spark plug... All of them, and check it against the book as well as the decal on the engine.. And be careful with the numbers on the dissy cap, both rotations are marked on the cap....

Chris.....
 
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armyofdux

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Re: Not reaching WOT

The plug wires were correct with respect to their plug. Did a Compression test this weekend... :( Port Engine failed, weak readings on cylinders 3, 6, 4. Starboard Engine was all within spec and only a few psi of each other (2-3). I tried the squirt oil trick in the cylinders and it made no difference so I am fairly convinced my compression loss is in the heads/valvetrain.

I am going to repower this winter but here is my question. If I just do a top end rebuild on the heads do you think I can milk it to the wintertime? I know it's going to put strain on the lower end but if I can get a couple of months out of it I would be happy.
 
achris

achris

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Re: Not reaching WOT

If the only problem is the valves, then a top-end overhaul is well in order. It should bring the engine back to life, and I don't believe it will put any extra stress on the lower end. I would also venture to say that once that's done, it will last quite a long time (several years at least)....

Chris.......
 
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