Seacraft 32. Twin 200 Yamaha 4 strokes!

[Was12]

My dad recently bought a 2000 seacraft 32. Before buying the boat we made sure that the updates were done to it and they were. When he bought it it had twin merc 225's and it ran 44 mph. We already had a set of Yamaha 200's from another boat so we repowered it with them. Every outboard dealer or anyone that knew about the 32 said it was going to be under powered but we figured we test them before getting a pair of bigger motors. The motors ran much better than expected. We have great hole shot and top speed. We are running 48.2 mph top speed and about 35 mph cruising at 4000 RPMs. The boat rides very well with the 200's. We ran in 3 to 5 ft seas from jupiter Fl to Marathon in 5 and a half hours which is about 195 miles. We only burnt about 110 gallons total and ran non stop.

[77SceptreOB]

That sounds good. I too am surprised that those twin 200s could produce that solid performance. Yamaha make a great motor.

[Capt Chuck]

I am wondering if you should lose an engine, I doubt that a single 200 would plane that hull

[Ryan]

Originally Posted by Capt Chuck

I am wondering if you should lose an engine, I doubt that a single 200 would plane that hull

well to be fair Chuck the 225 isnt going to plane it either.

[Was12]

I know that the 225 mercurys didn't push it on plane any better if not worse than the 200s so I know that the a single 225 isn't going to be pushing it. I will have to see what happens when I try to push it up with one engine.

[captbone]

If you have the time and effort to humor me.

Install a Mirage Plus 13pitch prop on one of the engines and I will bet a beer that it will plane and run 32mph+.

People will laugh at me but I certain. 16x13 Mirage Plus on one of the engines will plane off and run. Yes, 200hp on a 32ft Seacraft.

[gofastsandman]

Originally Posted by Was12

I know that the 225 mercurys didn't push it on plane any better if not worse than the 200s so I know that the a single 225 isn't going to be pushing it. I will have to see what happens when I try to push it up with one engine.

Your LU may not like that. Not much solace I know.

[FishStretcher]

The torque on the the gears will be the same, true. But the force from the higher thrust at lower speed will be resolved in the lower unit bearings. And the motor mounts. I don't design lower units, but I have a suspicion that this is something you can get away with for a time. Or at least get home and then tear down a LU and put new bearings in it. I suspect the gear teeth will be fine.

Just a guess.

[captbone]

Originally Posted by FishStretcher

The torque on the the gears will be the same, true. But the force from the higher thrust at lower speed will be resolved in the lower unit bearings. And the motor mounts. I don't design lower units, but I have a suspicion that this is something you can get away with for a time. Or at least get home and then tear down a LU and put new bearings in it. I suspect the gear teeth will be fine.

Just a guess.

The thrust is all the same. If the thrust was higher the boat would go faster. The speed in which the gearcase travels through the water or the amount of thrust producted at a given RPM is not relevant since the max thrust would be identical at WOT as long as it can reach the recommended wot rpm and peak hp.

Outboard engines that push barges, heavy boats, or tow a lot do not have a decrease in life simply because the engine can only product so much load, torque and thrust. Propped correctly, their is no increase in wear, tear or load regardless of what the outboard is pushing or the prop. Max is at WOT regardless of prop.

Just my 2 cents. I would gladly chip in to see the owner run a 13 pitch prop on one of the twins to see it break 30mph.

[gofastsandman]

Originally Posted by captbone

The thrust is all the same. If the thrust was higher the boat would go faster. The speed in which the gearcase travels through the water or the amount of thrust producted at a given RPM is not relevant since the max thrust would be identical at WOT as long as it can reach the recommended wot rpm and peak hp.

Outboard engines that push barges, heavy boats, or tow a lot do not have a decrease in life simply because the engine can only product so much load, torque and thrust. Propped correctly, their is no increase in wear, tear or load regardless of what the outboard is pushing or the prop. Max is at WOT regardless of prop.

Just my 2 cents. I would gladly chip in to see the owner run a 13 pitch prop on one of the twins to see it break 30mph.

Let me take my little brain off the short bus for a minnow. If 1 LU is being asked to push the same weight as 2 , is that not increasing the loads of torsion, shear, and compression?