Mercruiser 165 - in line six - basic questions

[David Foe]

I am new to mercruisers and this thing looks much more complicated than the atomic 4 in my sailboat that I have worked on for years (repairing and maintaining). I have an 18 (or is it 17?) ft Starcraft American from 1973 or so with a mercruiser 165 in line six, and associated outdrive. It works reasonably well but I'm trying to sort out a few questions and figure out what is normal and what isn't ...

(1) engine serial # is 3686519 -- this is a GM/chevy in line six what car equivalent would have had this engine?

(2) The out drive is 3701927 Am I right in calling this an Alpha Gen I?

(3) The trim tab/skeg on the stern drive is missing. This means the boat steers to one side which O can live with but it looks like it also acts as an anode. I'm in fresh water -- do I need to replace this asap? The boat lives in the water during the summer.

(4) I can't ever start the engine when it is cold from the idle position (cranks but no go) but can usually get it going by putting the throttle fairly far forward (say 2000 rpm when it is running). It won't idle (and therefore shift) until it has warmed up for quite a long while. Is this normal? If not what do I look at? One possibility is that the fuel priming pump isn't providing enough gas -- I usually have to give it 5 hard thrusts of the throttle to prime it. Is this normal? How do I check that the primer pump is allowing gas to get to the carb when I prime it?

(5) When it is started for the first time, how long is a normal warm up time? I guess I'm impatient but it seems to take 5-10 minutes before it works well (which it does when it is warm).


Sorry for all the questions but any insight would be really helpful.

David

 

[Bifflefan]

Re: Mercruiser 165 - in line six - basic questions

(1) engine serial # is 3686519 -- this is a GM/chevy in line six what car equivalent would have had this engine?

I do belive its based on the 250ci

(2) The out drive is 3701927 Am I right in calling this an Alpha Gen I?

Alpha Drive History

(3) The trim tab/skeg on the stern drive is missing. This means the boat steers to one side which O can live with but it looks like it also acts as an anode. I'm in fresh water -- do I need to replace this asap? The boat lives in the water during the summer.

You can get a replacement skeg and bolt it on. The tab behind the prop is also called a trim tab, you can adjust the torque steer with it, and yes you need the anode.

(4) I can't ever start the engine when it is cold from the idle position (cranks but no go) but can usually get it going by putting the throttle fairly far forward (say 2000 rpm when it is running). It won't idle (and therefore shift) until it has warmed up for quite a long while. Is this normal? If not what do I look at? One possibility is that the fuel priming pump isn't providing enough gas -- I usually have to give it 5 hard thrusts of the throttle to prime it. Is this normal? How do I check that the primer pump is allowing gas to get to the carb when I prime it?

Carb overhaul. Replace the fuel filters.
There is no primer pump or bulb. If the fuel pump was going bad, it would run out of gas when the engine was at a higher RPM.

(5) When it is started for the first time, how long is a normal warm up time? I guess I'm impatient but it seems to take 5-10 minutes before it works well (which it does when it is warm).

It should idle after a minute or 2 at most.

 

[TJDave]

Re: Mercruiser 165 - in line six - basic questions

Hi Dave,

I'm Dave. My previous boat had the trusty Merc. 165 Inline six. Was a 1973 Gulfstream that I owned for over 10 years and just gave to my neice's family. It was, and still is, a very reliable boat. The only problem I ever had with this motor was that the coil failed last season. It does not like to start on it's own when it has been sitting for more than a week. I prime it with a little spray of starting fluid through the air cleaner/spark arrestor, a little throttle, and she fires right up every time. If I am camping and/or using it everyday, she'll fire up with no help at all.

Yours should idle on it's own without any additional throttle even when cold. You can bump up the idle setting though.

Mine is cold blooded and took a good 5-10 minutes to warm up, or it would hiccup when I would give it gas. You have a working temp guage right? Any boat should be warmed up before you hit it anyway, IMO.

I'm no help with the adode thing. Mine had one. If it were me, I'd get another one if it came off my boat. It was turned about 5 degrees, I think.

I had to change out all the trim hoses because they were looking a bit rough. The two long ones that go from the pump to the hose fitting on the bottom of the outdrive were a PITA. Good luck with your boat.
Here's a pic of the outdrive and the anode about 5 degrees to the port side.
And the motor.

 

[Howard Sterndrive]

Re: Mercruiser 165 - in line six - basic questions

(4) I can't ever start the engine when it is cold from the idle position (cranks but no go) but can usually get it going by putting the throttle fairly far forward (say 2000 rpm when it is running).

that's going to be the case for every carbureted boat engine of that era.
It should idle once running though so you need to look for vacuum leaks and check out the carb and choke operation (service manual)

 

[David Foe]

Re: Mercruiser 165 - in line six - basic questions

Thanks for all the great information. My engine is exactly the one pictured by TJDave. My immediate problem is replacing the trim tab/anode assembly and finding the right part number for a Magnesium version of the anode for use in fresh water (lake Huron). The MC 165 parts blow up reveals that the Anode/trim tab assembly is part # 34127A1 but they don't provide a separate number for Magnesium. Where does one look for a Mg anode to fit this beast?

Thanks again, David