Engine swap: what is possible?

[EvilMoose]

Howdy, Newbie here....

I have a customer's 1972 Reinell equipped with a 120 OMC 4-banger engine sitting in my driveway. The engine block is cracked due to a previous owner's inattention, namely not letting the water out of the block(the previous owner was a little preoccupied, being deceased in a local cemetery, so I won't get too upset..lol). Since these engines are a bit on the difficult side to find in decent condition, and I am a hot rodder to begin with, what else will swap into the boat? It appears that the original engine is a GM variant(taller deck 151 CI, now a 181 CI)..or, what newer engines fit?

Thanks,
Elliott

[firestorm]

Originally Posted by EvilMoose

Howdy, Newbie here....

I have a customer's 1972 Reinell equipped with a 120 OMC 4-banger engine sitting in my driveway. The engine block is cracked due to a previous owner's inattention, namely not letting the water out of the block(the previous owner was a little preoccupied, being deceased in a local cemetery, so I won't get too upset..lol). Since these engines are a bit on the difficult side to find in decent condition, and I am a hot rodder to begin with, what else will swap into the boat? It appears that the original engine is a GM variant(taller deck 151 CI, now a 181 CI)..or, what newer engines fit?

Thanks,
Elliott

The only thing that will direct bolt in is a 2.5 or 3.0 4 banger GM block. Bell housing is a standard small block chev patern but mounts and everything else will need to be changed including the outdrive. The gear ratio will be wrong picture putting a small block in a vega and changing nothing else then run it for a hour or so WOT my bet is will not have a engine left unless you have a rev limiter and if you reprop it to handle the HP the outdrive won't survive you either can't get enough load to control the HP or you get enough load and blow the drive put a good running IRON DUKE in it and sell it for a faster boat.

[Gilbert]

Hi Moose,
I second firestorms comments and just add two things. You might like the boat just fine with a fresh iron duke. And marine engines are the equivalent of a Super Sport car engine; specifically, high performance pistons, etc. that can run all day without meltdown at high rpms so just sticking a standard short block for a Chevy II or what ever is not the same thing.
Cheers,
Gilbert

[firestorm]

I have to agree with Gilbert you may find the boat just fine with a 4 banger my position on selling to get a faster boat is cause you mentioned being a bit of a hot rodder. While a 120 or 140 I/O will get you up and down the river just fine not many every considered them a hot rod. Basiclly it comes down to what you plan on doing with the hull and if that is possible than how much power does it take to do it? depending on weight and size you might be able to get your boat in the 40-45 mph range with the right prop and good conditions. most of the speed charts for that I/O would give a 19ft runabout about 35mph top end with a 140 OMC which sounds slower than it feels when I was a kid we had a 12 Starcraft fishing boat with a 10hp merc that I thought was the fastest boat in the world and it probably never hit 22 mph. As to your problem there are lots of motors Avail on ebay and several companies that offer decent prices on rebuilds no core required. I have no idea what your budget is but I have seen several 3.0 engines listed as good running ready to install go in $500.00 range and rebuilt long blocks with warranties run from 1200.00-1700.00 .

[aCameronsdaddy]

I have worked at a maring shop for the last 3 years. While working there I was given a 4.3l v6 with a cracked block (mercruiser serial number tag on bellcrank). I rebuilt it with a auto-junkyard block of a year older.

With both stripped down, I discover MATCHING PARTNUMBERS on the cranks, cams and rods, (none on pistons). Despite all the hype I've heard over the years, it appears to me that in some cases the engines have only exterior mod added that make them MARINE.

Now about the 120 mercruiser, I installed this 4.3l in place of my 2.5L 120hp mercruiser. Here is what I did: I had a machine shop remove the ring gear off the 2.5l flywheel, and cut down the diameter of the 4.3l flywheel so the ring grar would fit it.
The 4.3l is a ballance shaft model so the difference in flywheel weight didn"t matter.
I had to modify the boat so the y-pipe would fit between the bilge stringers. I fabricated my own side motermounts, and pulleysystem for the cooling and alternator to fit the motor, I installed a new engine coupler (a 3.0 liter to fit in the bellhouseing-modified to bolt to the 4.3l). I used a new prop (fro 17p to 25pitch). I used marine started, alternator and ignition parts. I had to remove the jumpseats because the engine alot wider.
If this is what you have in mind, I hope this helps, It worked for me. I must tell you that my boat was way underpowered with the 120hp (20-30 sec to plane - now it takes about 6).
One last thought is this, It was a lot of work, a trihull may not give you the same results that I got with my deep-v. Don't know.

[just2fish]

Originally Posted by firestorm

The only thing that will direct bolt in is a 2.5 or 3.0 4 banger GM block. Bell housing is a standard small block chev patern but mounts and everything else will need to be changed including the outdrive. The gear ratio will be wrong picture putting a small block in a vega and changing nothing else then run it for a hour or so WOT my bet is will not have a engine left unless you have a rev limiter and if you reprop it to handle the HP the outdrive won't survive you either can't get enough load to control the HP or you get enough load and blow the drive put a good running IRON DUKE in it and sell it for a faster boat.

I have not been able to find a 2.5 120 omc Gm motor do you know of any for sale?

[just2fish]

if so please call 216.323.0338

[just2fish]

Any one with a motor for sale please let me know. I am looking for a 120 omc GM or other motor that I can bolt up with out making any changes.

[PAR]

A brand new, long block (181 GMC) is about $2,000, with turn key assemblies (just add oil) starting around $5,000.

Most every repair shop will have a worn out 181 laying around, that needs to be punched out and have it's internals replaced, which could be the stuff you already have.

Since you want a drop in engine, you choices are limited to a long block (swap over the external parts), turn key (drop in and run) or a crap shoot on a used engine and hope the seller is telling the truth about it's condition.

I've bought used boats, for less then $1,000, often around $500 with perfectly good 181's in them, still pulling 140 pounds of compression. Leg work and chasing bees off of old boats is the only way to find them. If it's by the road with a sign on it, then it's running and you'll pay for it. If it's under a tattered tarp in someone's car port, you'll get a deal.

[just2fish]

Ok thanks I think I got lucky and found a 120 omc for $4oo I will get it thursdsy or Friday the boat was in a car weack the motor was removed and sold to me How had is it going to be to remove and replace any tips? I have done lots of cars no boats. It looks easy enough.

[PAR]

It's similar stuff, just in a boat. Get the manual and lots of WD-40.

[just2fish]

HAving a hard time getting the drive shaft to line up anybody got any ideas? I tried it with the front mounts and the back mounts and just the back mounts it seems to be sliding back to far.

[gonzo]

The rear mounts are not adjustable. If they are collapsed you will not be able to align the engine. Are you using the aligning tool?