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General Mark Twain Discussion / Re: New Heads?
« Last post by Haulnazz15 on June 29, 2016, 09:37:34 AM »
Just for a reference, here's what I was dealing with:

Engine rear w/shift plate:

Engine installed, but top cap of the hull still separated to provide a lot of space over the carb to maneuver engine into bilge:

General Mark Twain Discussion / Re: New Heads?
« Last post by Haulnazz15 on June 29, 2016, 12:05:08 AM »
We both are running the 351W, however you have the OMC drive, where mine is a Mercruiser model.  I'm not too familiar with the stringer drive setup you have.  The Merc out drive is removed entirely, so there's nothing to support, the OMC unit it a different animal with the large flexible seal which could be more susceptible to damage if left unsupported.  I do believe that set screw is just for minor alignment adjustments, but I doubt it's of vital consequence.  It may just be for helping get the block-mounted portion to line up with the stringer-mount post.

I've not used, but I got mine from Rapido Marine and it was fine.  The only think I learned after some fussing with water trials is to make sure you check all of the ports on the front/back of the engine heads.  We chased down some exhaust leak noises thinking it was coming from the exhaust gaskets (pulled the manifolds twice) only to find that the block had open exhaust ports on the back of the heads (against the transom) which needed threaded plugs inserted to block off the holes.  Quick and easy fix once found, and those ports are only used on auto 351W's for the EGR system, so we never bothered to look at the back of the heads when dressing out the engine.
General Mark Twain Discussion / Re: New Heads?
« Last post by New2Me78 on June 28, 2016, 08:11:03 PM »
Did you have the outdrive supported when you pulled the motor? I think I have got just about everything unhooked that I need to. Getting ready to order an engine from "marineengines4less." They have an A+ rating from BBB & mostly positive reviews everywhere I've searched. $2,200 for a long block shipped. Don't know if you can help me with this or not (think your engine was a SB Chevy) firing order on my 351W is 13726548 which I have been told is standard rotation.
Pics I have enclosed are of the back mounts holding on the outdrive. I have had mixed comments from iboats forum that I HAVE to remove the outdrive before I remove the engine. With some supports under it back by the prop it appears to me that I could pull the engine out without outdrive removal.
Also included a picture of a set screw that is on both motor mounts. Do you know what these are for? Engine alignment?
The throttle cable should just be a standard Teleflex cable.  You'd need to measure it to make sure you have the correct length, though.
General Mark Twain Discussion / Re: New Heads?
« Last post by Haulnazz15 on June 28, 2016, 03:40:33 PM »
I did it all myself, including the transom repair.  It's really simple to pull the engine.  The only difficult part, at least on some of the Mark Twains, is the design of the engine bay/bilge.  My '76 has the convertible top storage and rope locker right above the flame arrestor/carburetor (like 1/2" clearance), so it involves some interesting logistics.  We used a normal engine hoist, but it barely worked and we had to remove the tires from one side of the trailer in order to drop the boat gunwale low enough to get the oil pan over it.

Basically, engine removal is something like this:
1) gear selector in FWD position, remove 6 nuts/washers from outdrive, 2 nuts from trim rams, and pull off outdrive.
2) disconnect throttle/shift cables from the throttle plate on rear of engine, as well as any electrical plugs/battery cables/fuel inlet hose from fuel tank.
3) Disconnect reverse trim lock hose from back of engine shift plate, then loosen exhaust y-tube connections to the exhaust risers
4) remove bolts from front engine mounts (2), and rear engine mount (2).
5) lift out engine entirely.

When we reinstalled, due to having worked on the transom, we had the top fiberglass cap separated from the hull section, so that gave us a few extra feet to work with, but it involves taking off the rub rails and removing screws/rivets up to the windshield, which is time consuming.  If I had to remove the engine again, I'd probably just remove the front engine mount bolts entirely and slide the engine forward as opposed to lifting it up. 
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My Throttle cable broke out on the lake Saturday.  I have had no luck finding a replacement.  There is a 90 degree turn  on the end that connects to the lever mechanism in the shift box.  Does anyone know where I can possibly get this cable?  Any help would be greatly appreciated. 

General Mark Twain Discussion / Re: New Heads?
« Last post by New2Me78 on June 12, 2016, 06:05:43 PM »
Yup same thing happened to me. Some water in cylinder 8 so I am having to start from ground zero. Funny you mentioned the exhaust manifolds. That's where this all started. I am really new to boating & was only told to open the block petcocks so the manifolds froze up. These were really old & cracks had already been welded shut so it didn't really bother me that they had to be replaced but the heads & block were good! >:(
Did you do the engine swap yourself or did you have somebody do it. The interior is already out & I have forklifts at work that I can use to pull it out so I might attempt to do this myself. I have done all this with autos but never done any of this kind of work on a boat.
General Mark Twain Discussion / Re: New Heads?
« Last post by Haulnazz15 on June 06, 2016, 10:56:00 AM »
There's definitely some heavy corrosion in there.  My worry would be less about the exhaust valve as those can be fixed up pretty easily.  If you haven't replaced the exhaust manifold/riser, I'd be inclined to do so at this time while everything's out.  If the water jacket has cracked or corroded through, it may just end up dumping water into the exhaust ports and hydro-locking a cylinder.  As far as the head is concerned, it's pretty easy to pull the heads and have them dissambled and hot-tanked to remove any major corrosion and inspect for cracks.

Short story long - When in the process of repairing the transom on our Twain, we pulled the 351w and let it set in the corner of the shop for a year or so.  Fast-forward to engine being put back in and ready to turn it over, the engine was frozen.  Turns out, once of the pistons had some water ingestion just prior to us pulling it and it sat until the piston rings rusted to the cylinder wall.  We had to hammer the piston out, and even then I decided it was easier just to get another long-block to swap in.  So, I'd take my time and make sure everything is right/solid before you go much further.  It'll save you a lot of time frustration. 

On the bright side for me, I have a new reman long block, which gave me the opportunity to upgrade to a 4bbl edelbrock carb/performer intake, as well as new center-riser style manifolds and risers which help the engine breath a bit more than the old log-style aft-risers.  She was orignially 233HP, but sits closer to 265HP or so, supposedly.
General Mark Twain Discussion / New Heads?
« Last post by New2Me78 on June 04, 2016, 08:05:00 PM »
I put this on another forum but have not gotten any response. It is a Twain so I will try it here too. After taking the exhaust manifolds off to replace them I noticed the port side head had A LOT of corrosion. Can this be cleaned up? Unfortunately I am thinking even if I could get all of the rust out the valves will be frozen it their seats. :( REALLY frustrated! Not only will this cost a lot but will probably kill my hopes of getting this restoration in the water this year.

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