Classic Fifty 45 HP Hesitating

[guck454]

I own a 77 Lund Pike 16 fishing boat. It came with a 81 2 cyl 40 hp merc with a 11" pitch prop. I replaced the motor with a 45 4 cyl with a 12" pitch prop. My problem is that the 40 would knock you out of the boat when you gave it WOT from an idle. The 45 on there now idles smoothly, goes at WOT all day, but seems to "lug" out of the water. Its top speed is 3-4 mph faster than the 40, but I don't think it could pull a skier out.

I just wanted to know if this is normal, and I shouldn't worry about it, just replace the plugs and lower lube like I do annually. Or should I start looking at timing or carb cleaning/adjustments. I did a compression test last fall and they were all 115-120#. I'm just wondering if I should tear into it before the season starts.

Also one colder day last Oct I warmed it up for several minutes, but it only hit on 3 for the first 1/2 mile then took off. Is this linked or just not fully warmed up. Any experience/ suggestions are greatly appreciated.

 

[tashasdaddy]

Re: Classic Fifty 45 HP Hesitating

carbs & timing, is my opinion here is some great info.

http://forums.iboats.com/showthread.php?t=168855

 

[halmc]

Re: Classic Fifty 45 HP Hesitating

I own a 77 Lund Pike 16 fishing boat. It came with a 81 2 cyl 40 hp merc with a 11" pitch prop. I replaced the motor with a 45 4 cyl with a 12" pitch prop. My problem is that the 40 would knock you out of the boat when you gave it WOT from an idle. The 45 on there now idles smoothly, goes at WOT all day, but seems to "lug" out of the water. Its top speed is 3-4 mph faster than the 40, but I don't think it could pull a skier out.

When you gave up that two cylinder you gave up some torque. The similarly sized four ain't gonna jerk your neck as well as the two cylinder. That said, the 12" prop sounds a bit tall to me, and your description fits that situation too. If you still have the prop off the two cyl, I'd give it a shot. Assuming it'll fit. In any case, I'd give up some pitch, which might even help your mph.

I just wanted to know if this is normal, and I shouldn't worry about it, just replace the plugs and lower lube like I do annually. Or should I start looking at timing or carb cleaning/adjustments. I did a compression test last fall and they were all 115-120#. I'm just wondering if I should tear into it before the season starts.

Don't fix it if it ain't baroque. To say that timing doesn't change much over time would be an understatment.

Also one colder day last Oct I warmed it up for several minutes, but it only hit on 3 for the first 1/2 mile then took off. Is this linked or just not fully warmed up. Any experience/ suggestions are greatly appreciated.

Assuming that you're sure that the missing is not the source of your performance complaints, it's no big deal. Probably a plug temporarily fouled from a bit of cold weather choking, or some such.

Lastly, I too have a classic fifty 4cyl, that I have grown to admire.

 

[guck454]

Re: Classic Fifty 45 HP Hesitating

Okay thanks guys. I have a manual and will time it. Is there anyway to check/change the timing with the motor still on the boat? I will also rebuild the carbs. I also considered getting a tach to play with props.