PDA

View Full Version : Changing an I/O engine to an inboard



scoffshore
07-30-2007, 02:30 PM
Ok not a Shamm, but I don't know a better group of guys to ask. In my buddy's Dyer 29, we are going to replace the 1972 Detroit Daytona Chevy inboard. We have looked at all different options, even diesel, but at the end of last week a friend who is upgrading his I/O power (bigger faster) offered to sell us his Mercruiser I/O engine with less than 100 hours for pocket change. What all will be involved for us to change this motor from an I/O to an inboard. We are thinking about just replacing the 72C transmission we have now anyways to make everything newer, but aren't sure. Thanks in advance guys!

Capt Don
07-30-2007, 11:15 PM
1) You will have to verify which direction it spins and make sure the trans is set up for the same rotation and the prop is correct.

2) On the I/O, the starter mounts on the block. On the Inboard the starter will more than likely mount on the Borg Warner bell housing on top. That means the ring gear on the flywheel will now be in the wrong place to make contact with the starter gear. You can heat the ring gear up with a torch and persuade it to the back of the flywheel, or just purchase an inboard flywheel.

3) You will probably need to install a wedge spacer under the carburetor to adjust for the tilt of an inboard engine because an I/O sits level. If not, float adjustments are a pain in the neck or impossible.

4) Forward engine mounts will be different. The I/O mounts will not have enough give in the rubber cushion to allow for the angle of installation.

5) Depending on the clearances you are dealing with in that boat, things like the alternator and raw water pump may need relocating.

6) I strongly suggest replacing the oil pan gaskets and rear main seal prior to installation because there will now be more oil laying against the back of the pan than there was before as an I/O where it was mounted level.

I can't think of anything elseat the moment, but I am tired. I'll see if any more comes to mind.

Don

scoffshore
07-31-2007, 08:10 AM
Wow, 63 views and only 1 response!

Capt Don the starter sits on top of the tranny right now on the daytona, and yes it sits on top of the engine on the merc, but on my indmar the starter was on the engine not the bellhousing. What gives. Figured we would have to replace the flywheel.

KevinK
07-31-2007, 08:22 AM
Maybe because 62 people have no idea how to answer that one...;) I sure don't - the header just caught my eye! I'm not sure I've ever talked with anyone about that kinda conversion. I'll leave it to the motorheads out there!

morning wood
07-31-2007, 01:22 PM
Capt. Don,
I had an opportunity to tow someone in the other day with my son's Shamrock.1986 Walkthru. The boat was a 38 foot S/F. I was amazed how true the boat tracked when towing in a seaway. The one question I have is what RPM becomes a strain on a Velvet Drive transmission with something heavy in tow? We made about 4 knots at 1800 rpms. His boat has a 350/260hp. I didn't want to tear anything up. Since you are in the business I thought I would ask.

Capt Don
07-31-2007, 10:24 PM
Wow, 63 views and only 1 response!

Capt Don the starter sits on top of the tranny right now on the daytona, and yes it sits on top of the engine on the merc, but on my indmar the starter was on the engine not the bellhousing. What gives. Figured we would have to replace the flywheel.


Your Indmar was probably a Ford. They all had the starters on the bell housing down alongside the engine. None of the Ford stuff will fit a Chevy.

Most of the Chevies had the starters on the Borg Warner bell housing on top. Not sure about the Daytona conversion, but those flywheel and starter parts won't work on the MerCruiser anyway.

I am surprised to hear the starter was on the top on a Merc I/O. Not sure as I have ever seen that before, unless it was a jack shaft type installation.

Capt Don
07-31-2007, 10:41 PM
Capt. Don,
I had an opportunity to tow someone in the other day with my son's Shamrock.1986 Walkthru. The boat was a 38 foot S/F. I was amazed how true the boat tracked when towing in a seaway. The one question I have is what RPM becomes a strain on a Velvet Drive transmission with something heavy in tow? We made about 4 knots at 1800 rpms. His boat has a 350/260hp. I didn't want to tear anything up. Since you are in the business I thought I would ask.

I typically tow at about 2500 rpm's. I can usually make between 5.5 and 7 knots, depending on the configuration of the vessel being towed. I have not burned up a Velvet Drive transmission yet.

These Shamrocks are bulletproof and an excellent choice for recreational vessel towing applications... in the right environment.

I was helping out a BoatUS operator one weekend in FL and was running his 20' Pilothouse with a 302 with a 2 barrel. Ended up getting a call to go out the Venice Jetties to get a 50' Sea Ray Sunudancer that had a bilge fire. There was an outgoing tide at about almost 3 knots in the jetties. Enough to make the channel markers posts sway back and forth in the current. There was an onshore wind of about 15 knots, kicking the seas onshore to about 3'. In the jetties the seas built to about 5', due to them stacking up against the current. The waves were about motionless, just rolling against the current.

Sound like fun?

I had to bring that Sea Ray in through that mess in that little 20 Pilot. Once in between the rock jetties, I had to crank it up to 3000 rpm's just to make 2 knots headway. I had to have my helper keep moving from the bow to the stern to help keep the boat weighted correctly to keep from stuffing the bow or the stern between the rollers.

Lots of folks got pictures of that one. It was about sunset time.

When I got to Marine Max, the owner of the Sea Ray said he lost sight of everything but the flasing light 3 times in the jetties between the waves, but figured I was still there because the line was still tight!

Anyway, I and most of the other tow guys out there will tell you the Velvet Drives are almost indestructable. Gotta keep good fluid in them and make sure the coolers are good.

BTW, you should see how much better these little boats tow with a true tow post in them. No comparison from towing from the stern eyes.

Here's a pic of me bringing in a 68' houseboat, towing a 20' bassboat and a 15 foot jetboat a couple weeks ago here on the lake. I was making 4.5 knots with them with a 150 Merc O/B. All three were broken down and at the same time.

morning wood
08-01-2007, 01:21 PM
Wow!!! That is amazing. We were helping out a friend and didn't realize how well the keel stabilized the boat. Thankyou for the information. Keep on towin!
Morning Wood

inverse121
08-02-2007, 10:12 AM
Wow, 63 views and only 1 response!

Capt Don the starter sits on top of the tranny right now on the daytona, and yes it sits on top of the engine on the merc, but on my indmar the starter was on the engine not the bellhousing. What gives. Figured we would have to replace the flywheel.

Well either Kurt is right or Don covered the bases. I had little to add above what Don said. Its a pretty straight forward conversion. Pretty close to a bolt in proposition. As a matter of fact, it seems the only way to go if you ask me. You can buy a Mercruiser set up for much less than a Marine Power inboard setup because Mercruiser pumps them out by the thousands.

I would buy some new trunion mounts if your current inboard mounts can't be salvaged.

Kurt
08-02-2007, 11:53 AM
Well either Kurt is right or Don covered the bases...
?????

Don't believe I posted in this thread - didn't want to stick foot in mouth.

inverse121
08-02-2007, 06:47 PM
?????

Don't believe I posted in this thread - didn't want to stick foot in mouth.

Sorry, Kurt, I mean Kevin, my fingers were working faster than my head. 'round here the K is usually followed by URT.