Can't get past 2300 RPM in gear

superdave5599

Recruit
Joined
May 14, 2009
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2
So I bought a newer boat earlier this week and have been working on getting it set up.

New boat: 1987 Century Bronco, 140 3L Mercruiser w/Alpha I stern drive. It is an 18 foot V-hull open bow boat.

(For reference) Old boat: 1977 Mark Twain, 120 hp Mercruiser w/ preAlpha stern drive. That one is a 16 foot tri-hull open bow boat.

Old boat was really pretty good at pulling tubers and skiers and would get up to 32ish MPH cruising.

We took the new boat for the first test drive last night, and it wouldn't go fast at all. (Not sure how slow it was, but nowhere near the speed of the old boat.)

Started thinking about things and thought that the prop might be the problem. So I swapped the props and put the hydrofoil on the new boat and took it out this morning expecting great things.

Nope. Just about as slow as last night.

It does seem though that the New Boat's prop and the old boat's prop may be similar pitch, though looking at them they seem different (different blade shape). The New Boat's prop is a Quicksilver Laser II and is marked 19 pitch. The old boat's prop, when googling the part number stamped on it, seems to also be a 19 pitch (though there is also a random 18 stamped on the side).

Today I took an "engine analyzer" (dwell, tach, etc) with me. In gear, the boat won't rev up past around 2300 RPM, even if we cruise for several minutes. In idle, it will rev up much higher easily.

So, can the prop having improper pitch make it not able to rev up, or will it just make it take longer to rev up?

Or should the engine eventually get up to speed no matter what prop?


Or should I be looking at the engine more? Cap and rotor are new, dwell is within range (about 30 degrees), timing seems right (8-9 deg btdc) and the carb seems to be adjusted right. The only thing I can think of is the PO put an electric fuel pump on and maybe it is shoving too much gas in?

Thoughts?

Thanks!
 
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