repowered my 24 Offshore and need advice

[plecofish]

Grady Nation,

Looking for advice.

I made the decision to upgrade motor on my 1987 Offshore 24 (closed transom, bracket)

I went from a 1995 Evinrude 225 carb to a 2000 Yamaha 250 Ox66 EFI.

Mechanic has the boat right now, installing motor, oil system, rigging with Yamaha controls and digital gauges. The current prop will be a 17 pitch stainless. All of which, came with the motor.

I have seen many similar year 1985-89 Offshores rigged with 250 hp around my boating area. My question is what would be the ideal cruising speed and RPM? Does a 17 pitch sound correct for a boat mostly used for fishing and family runs to the beach? Don't plan to do much skiing/tubing. I have to assume boat will run a bit different with this upgraded motor, prop etc.

I do plan to do a bay test with mechanic and listen to his advice, but would also like to hear from Grady guys with experience and this hull. Thank you for any input.

Plecofish

 

[Andrew93]

My old open transom 1986 Offshore with a 1997 225hp OX66 seemed to like 4300-4500 rpm at 24-26 knots from what I remember. I am sure the 250 will be a little better with the bracket, I also had a 17p stainless prop. It was not a rocket ship, but it was adequate for the boat.

 

[gw204]

Get the motor installed, running optimally (new plugs, clean O2 sensor, adjust TPS, adjust oil link rod, sync and lync) and see what kind of performance the current prop gives you. That's your baseline. Then you can start playing with engine height and props.

FYI...if your mechanic mounts the motor in the lowest holes, that will probably be too low. Put a straight edge along the hull bottom and make sure the anti-ventilation plate it at least 1-1/2" above the hull bottom. General rule is 1" up for every 12" of setback.

The motor will tell you when it's happy. All you have to do is listen.

 

[DennisG01]

I have a 17" Yamaha (17M) prop on mine. Engine is on a bracket. It runs right up to 5,500RPM's and even a bit more if I'm running light - which of course I can control via the throttle. I always prefer slightly underpropped as opposed to overpropped. I can't remember my fuel burn from last Summer (first season with it), but I seem to recall that it ran really nice around 3,500 - 4,000 RPM - maybe mid-twenties to upper 20's for speed. Top end was bout 40pmh. Sounds like you're using your boat for pretty much the same thing as me - all around type of stuff. I can tell you this - the boat is a rocket out of the hole! And that's WITHOUT even using tabs.

 

[plecofish]

Thanks you guys....exactly what I was looking for in way of advice.

Best of wishes in your boating seasons.

Be safe and tight lines fo those of you that fish!

 

[plecofish]

my next question is fuel for this motor.

Yamalube and use ringfree regularly?

I assume 89 octane is better suited for EFI?

 

[DennisG01]

89 is not needed, and certainly not because the engine is fuel injected. Do you put 89 octane in a car engine (designed for 87) just because it's fuel injected? The only justifiable (barely) reason for using 89 is if you know the fuel will sit for a long time without being used.

87 octane, a good quality TCW-3 2 cycle oil, Ring Free and Startron. You can't go wrong by using Yamalube, but according to multiple Yamaha technicians that I've talked to, it's not really any better than other good brands. In my stern drives, it's just Startron that I add. And... I'm never shy about the ratio of additives - better to err on the heavier side than lighter.

I occasionally sample fuel and the it's always been crystal clear -- other than the slight greenish tint it gets from the additives - for the 2-strokes, that is.

 

[plecofish]

Boat runs great, had a chance to run in calm conditions as well as with a stiff east wind out in the bay. Responded exactly as I hoped, as well as, the advice I got on here.

Dennis, thanks for the fuel info. The mechanic that rigged the motor echoed your thoughts.