Author Topic: 67 V172 20mph?? (Read 14979 times)

Jason · « **on:** September 27, 2010, 12:16:06 PM »

Took the V172 out for the first time this last weekend. Engine runs great. Pops out of the water and planes out quickly. But tops out at 20mph and 3000RPMS. If you don't remember it's a 95HP inline 6 merc with a 19p prop. My old 75 V173 would do 35 with a 85hp merc 4cyl so this should be at least equal to that in speed. I don't remember what prop I had on the 75 though.

In neatral it revs well past 5500RPM's quickly and smoothly.

I am hesitant to tare into the engine as it runs so good. Any ideas?

Rich_V174SS · « **Reply #1 on:** September 27, 2010, 12:27:24 PM »

I would think a 19p might be a little too big for that engine, I would try a 17p on it. I ran a 19 on my Merc 115 on a 1970 V176. Of course the engine will rev fine in neutral because there's no load on it. Check for fuel restrictions, clogged carb jets or a plugged vent on the tank. You should be getting 5500 rpm and around 35-40 mph wide open.

David CVX-16 · « **Reply #2 on:** September 27, 2010, 12:31:22 PM »

Start with Sea Foam in the gas tank, Mercury Power Tune in the carbs and combustion chambers, and check the condition of the spark plugs (and make sure they are the right ones for your motor.)

Jason · « **Reply #3 on:** September 27, 2010, 12:37:27 PM »

I haven't looked at anything on the engine yet. Just threw her in the water and see what happened. I'll check out the plugs, compression, fuel filters, vents, ect tonight. It's getting a new water pump impeller. Tattletale looked a little weak coming out of the side of the engine.

Dave, What kind of props do you have laying around that will fit this thing for me to try out?

David CVX-16 · « **Reply #4 on:** September 27, 2010, 12:42:55 PM »

I just have 19 and 21 pitch SS Ballistic and 21 pitch 2-blade bronze. Check with Steve, Ross or Jim who may have 17's and 19's.

Hotwired · « **Reply #5 on:** September 27, 2010, 01:14:27 PM »

Be interesting to see what the 17 or even a 15 inch prop will do.

David CVX-16 · « **Reply #6 on:** September 27, 2010, 02:18:31 PM »

Also change the fuel diaphram rubber, gaskets and check valves (comes as a kit). I would think that a 19" pitch prop would work. It depends in the lower unit gears. The 115 HP Merc has 2 to 1 gears, but my 80 HP Merc had 2.3 to 1 so the V-153 used the same 19" and 21" props with both the 80 HP and 115 HP Merc.

Tonka Jim · « **Reply #7 on:** September 27, 2010, 02:34:42 PM »

Quote from: David on September 27, 2010, 12:42:55 PM

Check with Steve, Ross or Jim who may have 17's and 19's.

I don't have a 17 and I don't think Steve A. does.
Ross might
I got one from Lance at Lance's Prop Shop in Forest Lake this spring to try but traded it back for a 19.

Jim B

Jason · « **Reply #8 on:** September 27, 2010, 03:04:51 PM »

I am starting to really think the prop is fine. It jumps out of the water and planes really quick. There must be something else going on. I'll look into the motor tonight.

Hyperacme · « **Reply #9 on:** September 27, 2010, 03:57:49 PM »

Jason where is the trim pin set to ?
Should be 3rd or 4th out ...

EDIT
Just looked at your post and you have power tilt & trim ...

David CVX-16 · « **Reply #10 on:** September 27, 2010, 04:16:21 PM »

Another question is whether or not the engine is laboring at full throttle. If so, check the motor angle as Gregg suggested, or check the bottom of the hull for hooks or rockers or growth. If not laboring, a fuel or electrical problem, a slipping rubber hub in the prop, or a prop with a really low pitch, such as 11", 13" or 15". Good luck.

instep · « **Reply #11 on:** September 27, 2010, 04:46:31 PM »

Had the same problem ,it was a small air leak in the primer bulb and another time it was a small hole in the fuel pump diaphram(chrysler) if it jumps out of hole shot than loses pwr probably check eintire fuel system.

Jason · « **Reply #12 on:** September 27, 2010, 07:42:45 PM »

Well, looked at her again tonight. I was wrong on the prop. It IS a 17P prop and looks new so kind of doubt it's that at all now. If anything the RPM's would be high.

I noticed the throttle lever is rotating all the way to the stop screw on the distributer but you can manually move the carb linkage a little more, maybe 15 degrees or so before it hits the stops on the carbs. Is this normal?

Compression was 150psi across all 6. So that's good.

Spark plugs were pretty carboned up. They are Champion plugs which have let me down in the past so i think I'll replace them anyway.

It does have power trim and I tried it at all angles. Someone put the hydrofoils on there. Think that would affect anything?

Growth on the bottom....... You might be onto something Dave. I noticed it before but didn't realize it was as bad as it is. Feels like REALLY ruff sandpaper. Think it could affect it this much? I guess I should work it off anyway. Not looking forward to that!

Hyperacme · « **Reply #13 on:** September 27, 2010, 08:05:03 PM »

HOLY CRAP !
What is that ?

David CVX-16 · « **Reply #14 on:** September 27, 2010, 08:07:37 PM »

Looks like growth is the problem, but do the other stuff too just because you do not know when it was done before. There should be some algee or industrial cleaner that would take care of the growth. I personally like NGK plugs, but Steve likes the Champions. NGK for mine is BUHW, Champion is L78V. Check a marine dealer for your number. Fleet Farm has both, about $2.25 for the NGK's.

Hotwired · « **Reply #15 on:** September 27, 2010, 08:09:38 PM »

WOW!!! ya .. that will certainly slow you down!

Rosscoe · « **Reply #16 on:** September 27, 2010, 08:11:51 PM »

Wow that bottom looks hairy! Might have to shave that bugger. Is it from the middle east?

I know less then the others that made suggestions so....
That thing sure should be able to spin a 17"

CVX Fever · « **Reply #17 on:** September 27, 2010, 08:54:35 PM »

Wow Jason, I'll concur with others that the growth on the bottom of the hull has to be giving you problems. Up in Eagle River last weekend?

Jason · « **Reply #18 on:** September 27, 2010, 09:55:13 PM »

Rhinelander!

yep, got some serious scrubbing to do. It's really caked on there. Any ideas on what will work to remove this?

Hotwired · « **Reply #19 on:** September 28, 2010, 11:43:56 AM »

The little bit I have read it sounds like you can power wash it off after you let it sit in the water for a while and saturates with water.