Replaced upper drive now boat is plowing through the water

[Tconn]

I have a 1990 Thompson Carrera 205 with a 4.3 l mer ruiser and alpha one outdrive 1.84 gears when I bought it everything was fine the boat ran at 40 miles an hour and steered great no plowing. After a couple times in the water the upper gears went out because the previous owner filled the oil from the top. so I bought a new outdrive geared the same put it all back together and now the boat only does 30 miles an hour. The bow plows through the water and is hard to steer. You need a raincoat to be in the boat at full throttle What could I have done wrong?

 

[alldodge]

Howdy

Are you trimming the drive up any?

 

[Bondo]

Ayuh,.... Welcome Aboard,....

Same gear ratio,..??
Same Prop,..??
Are ya trimmin' up,..??

 

[Tconn]

Yes I trim up when i get on plane very minimal change. I have tried all different levels of trim. Also yes same prop and gears

 

[alldodge]

Yes I trim up when i get on plane very minimal change. I have tried all different levels of trim. Also yes same prop and gears

Sorry not saying you don't know what your doing, just want to make sure. When you push the trim up button are you sure the drive is trimming up? Might hear the trim motor run but maybe it needs oil

 

[Tconn]

It's ok and yes I'm sure it comes up as the boat picks up a little speed and also it comes up in shallow water and when i trailer it

 

[alldodge]

That's just weird, hence your question. Can you post a pic of the drive full down and the stern of the boat even with the Cav plate?

If you still have the old drive I would like a pic of it as well. Wonder if there is a depth difference in the drive :noidea:

 

[Tconn]

I Re-read my original question I did not change the whole outdrive I only changed the upper unit. Sorry. But I will check to see if the guy still has the old upper unit but as the new one and the old one sat side-by-side I do not recall any difference

 

[alldodge]

I Re-read my original question I did not change the whole outdrive I only changed the upper unit. Sorry. But I will check to see if the guy still has the old upper unit but as the new one and the old one sat side-by-side I do not recall any difference

Oh, in most all cases this is not good at all. If the upper goes out, the shavings which come apart in the upper go to the lower. Unless the lower was taken apart, cleaned and reassembled, you might have an issue going on.

Lets say that is not an issue, but the upper also has different ratios and I'm going to bet that a different ratio was installed. Does your motor reach the same rpm levels?

 

[Tconn]

Lower was flushed and cleaned very well even know there were no shavings in it. The upper has 1.84 stamped on it just like the old one did. And yes I get the same rpm about 4400 to 4500 but 10 mph slower now which I would guess is from plowing through the water. When on boat it feels level. But it has to b plowin because I throw tons of water over the sides of the bow into the boat

 

[alldodge]

yes I get the same rpm about 4400 to 4500 but 10 mph slower now which I would guess is from plowing through the water.

OK, then same rpm, lower speed and plowing water, means the nose of the boat is not coming up. If it was less rpm then we could look at ratio, but same rpm and nose down means only the trim is not coming up due to trim is not moving, or something is creating one heck of a drag that was not there before. So need some pics

 

[HT32BSX115]

I think I would verify the ratio by turning the engine and counting prop blades or opening it up on top and count teeth.......
Unless the replacement drive is new out of the box, I wouldn't be betting on the ratio.

 

[Tconn]

 

[Tconn]

These r all I have for now and it is not all the way trimmed down but close its as far as i could go at the time

 

[Alumarine]

Do you have your trim tabs fully up when trying it out?

If you are going 30 mph then it must be on plane.

You should be able to control the bow angle by either trimming the leg up or down or putting the trim tabs up or down.

In your picture the trim tabs in that position would force the bow down and might cause you to plow.
Try it with the tabs fully up and start trimming the drive up a bit.

Also you don't need the trim tabs and the foil on the drive.
I'd lose the foil.
It's like wearing suspenders with a belt.

 

[Tconn]

Ok I was thinkin about takin that off. But as for the trim tabs thats as far up as they go or have ever gone at least since I've had the boat the couple months

 

[Alumarine]

Ok I was thinkin about takin that off. But as for the trim tabs thats as far up as they go or have ever gone at least since I've had the boat the couple months

The cylinders will go about 3" more in/higher.
It looks like they are fully deployed.

That will stuff your bow good.

 

[Alumarine]

This is what they should look like in the full up position.
I have 1.75" of piston shaft from the horizontal pin to the bottom of the cylinder.
Your's might be different but it should be close.

 

[alldodge]

Marc, I think you have found the problem. Those tabs are way to far down

 

[Tconn]

Ok I will mess with the tabs hopefully sunday when i get a day off and let u guys know thanks for the help hope that's the problem