Can you put an OMC 5.0 outdrive and put it on a OMC 5.7?

[Canmex_boater]

Hello,
We have a 25' 1988 Larson DC-250 and we have been having problems with the speed of the boat. The engine runs fine so we are thinking it is the outdrive. We have found a used 5.0 lt OMC, but our boat is a 5.7 lt.
Just wondering if anyone knows if this would be compatible to just take the old one off and put the new one on or if it is a bad idea.
Also I saw on another post that we may need to change prop size. We are running a 15X17 prop right now, would that work with the new 5.0 outdrive.
Any advice helps thank you.

 

[HT32BSX115]

Hello,
We have a 25' 1988 Larson DC-250 and we have been having problems with the speed of the boat. The engine runs fine so we are thinking it is the outdrive. We have found a used 5.0 lt OMC, but our boat is a 5.7 lt.
Just wondering if anyone knows if this would be compatible to just take the old one off and put the new one on or if it is a bad idea.
Also I saw on another post that we may need to change prop size. We are running a 15X17 prop right now, would that work with the new 5.0 outdrive.
Any advice helps thank you.

Howdy,

Welcome aboard!

It usually helps if you post your engine/drive model number so we have a complete picture of what you have.
Your engine could be one of the following:

574AMLGDP 1988
574APRGDP 1988
574BMLGDP 1988
574BPRGDP 1988


574AMFTC 1987
574APARY 1987
574APFTC 1987
574APSRC 1987


If your drive is original, it should be a 1.41:1 Ratio drive.

There are many NON-out drive things that affect the top speed of your boat.
An out drive is usually either working correctly or it's not. There not much "in between"

Here's a good place to start when you cannot make top speed.

http://forums.iboats.com/forum/engi...69-must-have-technical-information-for-diyers

take a look at all the items in the list but for your problem, focus particularly on #14

Regards,

Rick

 

[ondarvr]

What is it that leads you to believe the outdrive is the issue?

 

[Canmex_boater]

The problem we have been having with our boat is when it reaches around 10 miles per hour there is a loud grinding noise and we stop giving it gas because it sounds like it could majorly damage the engine. It also smells like burnt rubber right after that.
We can run the boat outside of the water full speed with the prop going and it does just fine. No noise no smell. The last time we ran it in the water I watched the inboard engine and everything looked fine when the noise occurred. All of the pulleys kept turning. Nothing shaking or smoking. And the noise sounds like it is coming from the back or outdrive.
The engine with the boat is the original engine that came with the boat.

 

[HT32BSX115]

The problem we have been having with our boat is when it reaches around 10 miles per hour there is a loud grinding noise and we stop giving it gas because it sounds like it could majorly damage the engine. It also smells like burnt rubber right after that.

Get a flashlight and look carefully behind the engine near the transom and in the bilge below the rear of the engine. Do you see anything that looks like black powder or powdered rubber?

 

[JJBoatr]

Sounds like the drive coupler let go to me.

 

[Canmex_boater]

We have figured out that it is the coupler, we have had this problem for 2 years. Finally we know what is wrong but all I have read says you have to pull the inboard engine out to fix the problem. We are about to get married so we don't have the time to fix a problem that extensive right now. My question is can we continue to use it maybe 2 more times without causing serious damage to the boat. We stay going slow and it doesn't make the noise, and we have been driving it with this problem for 2 years already. We are planning on fixing it in about a month after the wedding and honeymoon. Another question I have is do you think we could just slide the engine forward enough to get to the coupler? Or does the engine for sure have to be removed. Any advice helps. Thank you

 

[HT32BSX115]

We have figured out that it is the coupler, we have had this problem for 2 years. Finally we know what is wrong but all I have read says you have to pull the inboard engine out to fix the problem. We are about to get married so we don't have the time to fix a problem that extensive right now. My question is can we continue to use it maybe 2 more times without causing serious damage to the boat. We stay going slow and it doesn't make the noise, and we have been driving it with this problem for 2 years already. We are planning on fixing it in about a month after the wedding and honeymoon. Another question I have is do you think we could just slide the engine forward enough to get to the coupler? Or does the engine for sure have to be removed. Any advice helps. Thank you

You'll need to first remove the drive and then pull the engine far enough forward to remove and replace the coupler.

That, under normal circumstances, always requires lifting the engine all the way out. (it's not that hard to remove an I/O engine)

You might be able to operate the boat only at idle, but the coupler will fail completely and strand you, and it'll happen without warning. NOy many people here that would suggest you try to run it even at idle.