TOPIC: Best Prop Pitch for a 1960 Merc 400

I am running a 13" pitch prop (p/n A-48-29986A2-13) on my 1960 Merc 400/ 1960 G3. This past spring I replaced the magneto with a rebuit unit, rebuilt the fuel pump, replaced fuel lines, and adjusted mag and throttle linkage, hoping to improve top speed over what I was getting last summer (27mph on GPS). This summer the best I can reach is 22mph. I'm bummed!! Unfortunately I don't have a reliable tach, but the engine runs very well and sounds good.

I am thinking of trying to find a 15" or higher prop but I am hoping someone running a similar setup or who has more experience in prop selection that I have will weigh in here and point me in the right direction. And no, OMC isn't the direction I am looking for here!!

I hope to get a 1960 Merc 700DR rebuilt this winter for this same boat. Any recommendations for a prop for that engine/ boat setup?

Thanks for any help.

dseaver:

I don't know if this will help you much but we have a 2009 Mercury 50 H.P. Two-Stroke on our 1960 G-3 and I am running a 15 pitch prop on the motor right now. With both my Wife and I in the boat I see about 38 MPH at WOT and RPM at about 5400.

Go on a Diet , I should talk.... As U changed the mag, U think maybe you screwed up on the linkage adjustments? A tach is a good investment...

g3bill, I am working on that diet, but ice on the lake is coming quicker than my target weight of 100#. I did spend time with the linkage since I had the throttle control unit apart and back together as well as the other work. I know the throttles are opening fully upon mag advance. Could I be missing something else?

you will need to get your timming back into shape, since you changed the mag and lost spd, I would say you must have changed your wot timming. a 13p prop is probly just about correct for your app. adding pitch now might ruin your motor

Jeff's so right, Timing is what I left out? Very critical point getting timing just right. If you don't have the Manual think on getting one, or just ask. Use primium gas imo.

My main puter is down so cant post the timing tool?

Hi to all who replied regarding my prop question which turned into a question of proper timing. This is an update. Last week I took the boat from West Michigan, where I live, out to Lake Ontario (Buffalo area) to have Larry Downs check out the timing and verify I had set it up correctly. I had bought my rebuilt mag from Larry late winter.I wanted to learn how to check dwell, advance, etc. since I didn't totally understand my service manual and also didn't have a tester. Larry bench tested the mag again, verified dwell, and checked timing advance. Everything checks out perfectly, except I had the timing advanced to .283" instead of factory spec of .235". We left the timing at .283". So....the big issue of mag timing is eliminated. Compresion last year was checked at :140#,138#,138",135#
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