automotive 351 windsor (1981) engine in to replace a seized marine 302 (1976)

[axeroad]

Will most marine parts bolt on to the 351......or do I need to go with another 302?

 

[Scott Danforth]

welcome aboaurd

your 302 was a mixed bag of ford and specialty marine parts assembled by Mercruiser. it most likely had the 351 marine cam in it as well as different heads.

if you are pulling a truck motor, you need to strip it down to the block and heads, replace teh core plugs with brass, use marine head gaskets, a marine circulating pump, the marine intake manifold (cast iron or dual alloy aluminum/bronze)

 

[axeroad]

Sounds like I should find a marine 302 instead. Maybe I will try removing the top end and see if it will free up with a hammer and piece of wood. It appears to be terminal anyway.

I have had it soaking in a mix of diesel and ATF (5 gallon pail of it on top of the regular oil already in the pan) for a few days but still won't budge. Heavy bolts through the square ports in the harmonic balancer and a 4' snipe with all of my 180lbs on the end.... gently spring loading it of course.

I even had a single burner hotplate right up under the oil pan, whole block got warm and the pan was hot to the touch but no go. I will let it soak a few more days (plugs out, penetration oil in). After that I guess entertainment during removal is about all I can hope for now.

 

[Bondo]

Ayuh,.... Welcome Aboard,..... More likely the cylinders are rusted 'round the pistons,.....

 

[Scott Danforth]

If its rusted, even if you get it free, not sure it would run for any length of time...rusted bores eat rings.

You may just have to talk to your local machine shop and rebuild one of them

 

[axeroad]

I do have a couple excellent 351 windsors, one in an old shorty school bus and another in an econoline. If I pulled one out to use and I understand you correctly I could use the short block as is (with those plugs changed to brass) and then the same heads with new marine head gaskets.

Then the marine manifold and circulating pump etc from the old 302 merccruiser may bolt on? ....or do I need to find those items specifically for a 351?

I do have a second old 302 in the back yard from another boat, I guess tearing them both down to see what is useable for a rebuild as you say. That may be another option instead of the 351 truck engine. Just thought it might be easier/less costly and possible more horsepower for the big old Skagit fibreglass hull.

 

[kenny nunez]

If you end up going the 351 route be sure to use a 351 flywheel or you may end up with a an un balanced engine.
If you stay with a 302 do like Scott said and either a new 351 cam or be sure to keep the lifters in order if you re use the original cam from the frozen engine.
Another thing to look at is the 302 marine distributor which is different from a 351 and they do not interchange. Most of the other external hardware should fit. The 351 needs a 4 barrel marine carburetor which will give you around 240 hp.

 

[axeroad]

Well thank you for all that valuable info..... it will certainly help me with the final decision.
I have never rebuilt an engine...... so my concerns here were what will easily swap over and what will not.

 

[axeroad]

Discovered my other engines were 351M's so couldn't use them.....abandoned the project until about mid June when I decided to get on my 36" (not 4') snipe again...... well it moved!
It had been soaking in about 25 litres of an ATF/Diesel mix (to top of dipstick tube) for 3 weeks.

Well great, so I reset my snipe for another 1/8th turn and so on. Thought I had I solved until it jammed again, so I applied more torque and broke the casting hub of the balancer at the same time that I managed to cam over the resistance. I was then able to move the engine with a ratchet and socket. It did become quite free and I could turn it over with the starter.

Drained all the old fluids from block and filter. Refilled with just straight oily diesel and ran starter a bit to circulate. Heard some clacking so I removed the valve cover. Freed two sticky valves and removed a pretzelled push rod....haha, remember this was just to be entertainment before removal.

Still had that old 188 block laying under a tree .....correct balancer and proper push rod. Installed my new parts and had no more noises!. Rotated her on the starter, oily diesel was coming over the rockers and all seemed well. Put the covers back on, completely drained to drip dry. Then added new motor oil and a filter. Rolled it over some more for good lube.

Had to go through some pain to make sure distributer cap, wires and plugs were all correct and ready to fire. Filled the float bowl but it just wouldn't fire. Finally after dumping a lot of fuel directly in and furiously pumping the throttle it blasted to life. Almost full throttle, funny car flames, right out the heads before it stalled.

There I was in my driveway within a MASSIVE cloud of smoke caused by burned penetrating oil, ATF, diesel. etc.
Caught it on the second try and was able to maintain control through a short test of different revs right down to idle.
I shut it off after 45 seconds or so.

Next evening after work it fired up immediately and ran smooth. Today I tried again, sounds good enough to me..... going to bolt the exhaust manifolds on and add water next..... maybe tomorrow.
Not quite ready to remove that old 302 just yet. Regards.