Mercruiser 165hp Inline 6 questions

Waffle

Seaman
Joined
Jul 21, 2007
Messages
64
Hi all. Have tried to use the search feature and I am just not getting it.

My Dad gave me his old boat about a month ago. Title and registration both say the boat is a 1970 19' boat. But it doesn't give a brand name, just the plaque on the transom says "Manufactured by Fish-n-Ski Marine Products Inc." I have done extensive searching of the net trying to find out more specifics of the boat to no avail.

That said, I do know that the engine is a straight six 250 ci. The boat works great except when I try to go from a stop to WOT. She sputters and spits and backfires until the RPMS get to certain point then she runs fine. It runs best if I give it the throttle slowly and eventually get on plane, but we are looking to do some skiing soon and need more throttle response.

I am not sure when the last tune up was performed and if the person/people that did it knew what they were doing. The oil is dirty but it is all oil and no water. I tried adjusting the carb in the drive way, but it didn't seem to change anything. The pcv valve doesn't look like it is tight in the manifold, therefore maybe not delivering enough warm air to the carb? I think maybe the pcv is my problem for the most part, but want to get this thing running like a top.

So here are my questions.

1. Are marine parts needed as replacements for points, cap, rotor, plugs, and wires?

2. What are the timing specs, gaps recommended?

3. What is the baseline for the carb screw positions?

4. What is the best way to get the old oil out? (I do have a hand held pump, but am not sure if I can suck the oil from suction at the top of the dipstick or do I need to buy a smaller tube to run down the oil check?)

5. What is the oil capacity with a filter change and do I fill the filter before installing?



5.
 

95yj

Petty Officer 1st Class
Joined
Feb 21, 2007
Messages
279
Re: Mercruiser 165hp Inline 6 questions

First off, you're problem sounds like an accelerator pump issue on the carb. Adjusting the idle mixture won't help. Now that you've mucked with the idle mixture, it's probably off and needs to be reset but you need to make sure that you've got a good tune up first.
 

Waffle

Seaman
Joined
Jul 21, 2007
Messages
64
Re: Mercruiser 165hp Inline 6 questions

Thanks for the reply.
 

ziggy

Admiral
Joined
Jun 30, 2004
Messages
7,473
Re: Mercruiser 165hp Inline 6 questions

1. Are marine parts needed as replacements for points, cap, rotor, plugs, and wires?
ya, ya should use marine tune up parts. but proabably can get away with good quality auto plug wires
2. What are the timing specs, gaps recommended?
compression pressure, 140psi
point gap.016
point dwell, 31-34 degrees
plug gap .035
timing @ idle 6 degrees btdc
max rpm @ wot 3900-4300
idle rpm 500-600
fuel pump pressure 3.5-4.5 psi

3. What is the baseline for the carb screw positions?
i don't know and can't find it in the book. my 75 L6 is 1 1/4 turns out to start, adj. from there....

4. What is the best way to get the old oil out? (I do have a hand held pump, but am not sure if I can suck the oil from suction at the top of the dipstick or do I need to buy a smaller tube to run down the oil check?)
i use a small tube and go down the dipstick hole and suck it out.....
5. What is the oil capacity with a filter change and do I fill the filter before installing?
book says 5 qts. for oil quanity. i think i put in about 4.5 qts w/ the small filter from personal expereince. i also don't pre-fill the oil filter

i think ya should do yer tune first, then see where that leads ya for yer bog.
Adjusting the idle mixture won't help.
that's ture. idle mix screw adj. only the idle circut of the carb. nothing else.....
 

ParallaxBill

Petty Officer 1st Class
Joined
Aug 27, 2006
Messages
341
Re: Mercruiser 165hp Inline 6 questions

I'd recommend rebuilding the carb and do a thorough tune-up. My other advice mirrors ziggy's since we are running the same engines.
 

Waffle

Seaman
Joined
Jul 21, 2007
Messages
64
Re: Mercruiser 165hp Inline 6 questions

Thanks for the replies. I will be ordering a service manual soon, but wanted to get that information now so I can get her running strong again. Tune up first, then see how she handles. If she still isn't up to snuff then to the carb I go.
 

ParallaxBill

Petty Officer 1st Class
Joined
Aug 27, 2006
Messages
341
Re: Mercruiser 165hp Inline 6 questions

There are a good number of us here on iboats that still run that engine/outdrive combo so you will have plenty of help getting it running just right. It was a great set-up for the larger heavier boats of that era and the engine itself is bullet proof when tuned and maintained properly.

Ran one for what seemed an eternity in a 1978 Chevy PU back in the day. The engine never once gave me the first bit of a problem. Peripherals like replacing worn out alternator's, water pumps, belts and routine tune-ups was all she ever asked for.
 

Waffle

Seaman
Joined
Jul 21, 2007
Messages
64
Re: Mercruiser 165hp Inline 6 questions

You guys rock.

Ziggy, thanks so much for taking the time to type that out. If you guys are interested I am also trying to ID my boat in another thread. with pics. Bill, what part of NC are you from? Dad lives on the Neuse between Newbern and Oriental, hence the saltwater boat turned fresh.

95yj please tell me what I am looking for on the accelerator pump.

Anyway, pics here http://forums.iboats.com/showthread.php?t=209980
 

95yj

Petty Officer 1st Class
Joined
Feb 21, 2007
Messages
279
Re: Mercruiser 165hp Inline 6 questions

Accelerator pump squirts gas into the carb when you hit the throttle to make up for the instant lean out condition of the throttle plates opening. Look down the carb and hit the throttle and you should see a good stream of gas flow into each barrel. If not, your accelerator pump is bad and you might as well rebuild the entire carb.
 

ParallaxBill

Petty Officer 1st Class
Joined
Aug 27, 2006
Messages
341
Re: Mercruiser 165hp Inline 6 questions

waffle, I'm southeast of Charlotte between the Catawba river system and the Yadkin/PeeDee basin. Good lakes all around.:)
 
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