140hp 4 cylinder, swap to 4.3L v6 or 5.7L v8. Few questions

[Tfreestyle]

I have a 1990 Marlin 19' cuddy cabin. It currently has a mercruiser 140hp 4 cylinder that is toast and a mercruiser alpha 1. Instead of spending the money on an underpowered replacement I am looking to swap to a 4.3L or 5.7L. I will be using the boat probably more on the ocean then the lake so the extra power would be nice. So far this is what I have questions on...

the outdrive gear ratio will now be off, can a prop change cure this or will I need a different outdrive? I think the v6 will be ok with a prop change, not sure on the v8 though

What else am I looking at having to upgrade or change to do this swap, fuel pump maybe? exhaust routing?

When I do go to resell this boat eventually will the bigger motor make the boat worth more or will it probably sell for the same price as the 140hp would get?

Im thinking the headaches of the swap will be worth the extra power but want to make sure im making the right decision. When I do go to buy the motor I will be looking on craigslist and businesses that sell used motors so I can get a direct drop in with all the parts still on the motor and save cash.

If this were your boat what would you do motor wise?

 

[Don S]

Re: 140hp 4 cylinder, swap to 4.3L v6 or 5.7L v8. Few questions

the outdrive gear ratio will now be off, can a prop change cure this or will I need a different outdrive?

If you want to take advantage of the bigger engine, you need the correct gear ratio. Otherwise you are just changing rpm.

The reason for the gear ratios is to keep you in a usable prop range.

What else am I looking at having to upgrade or change to do this swap, fuel pump maybe? exhaust routing?

Everything.. Nothing on the 3.0L will work on the V engines. Exhaust Y to transom shield if they have the right bolt pattern.

Do you have stringers to mount the side engine mounts too? Are they spaced right?
Will the engine cover fit over the bigger engine?

 

[Bondo]

Re: 140hp 4 cylinder, swap to 4.3L v6 or 5.7L v8. Few questions

the outdrive gear ratio will now be off, can a prop change cure this or will I need a different outdrive? I think the v6 will be ok with a prop change, not sure on the v8 though

Ayuh,.... You'll need a differently geared drive,... Changin' props Won't work...

 

[ONEGA]

Re: 140hp 4 cylinder, swap to 4.3L v6 or 5.7L v8. Few questions

Instead of spending the money on an underpowered replacement I am looking to swap to a 4.3L or 5.7L.

View attachment 183983View attachment 183984

If you don't have complete 4.3 or 5.7 drivetrain on hand you will have to keep this boat forever after you spend all that money and labor on this repower. I don't think it's underpowered with original motor though...so do your math first.
Just my 0.02

 

[Tfreestyle]

Re: 140hp 4 cylinder, swap to 4.3L v6 or 5.7L v8. Few questions

well I think having to switch to a different drive is the killer for me, I really dont want to deal with buying another drive and then trying to resell the one I have. I found an engine with approximately 400 hours and the head was just rebuilt at a shop down in san diego for $900 and then another unknown hour engine for $650. both complete with all accessories. Leaning towards the $900 unless I can talk down the $650 guy to like $300-350

 

[Don S]

Re: 140hp 4 cylinder, swap to 4.3L v6 or 5.7L v8. Few questions

You only have to change the upper, not the whole drive. Sterndrive Engineering