Is the 351w-w/ Lightning direct replacement for a 1994 Pro Boss 5.8 (carb, Pro Tec)?

[ddumbauld]

84 – 05

5.8 Liter 351W- W/ Lightning (D3OZ-6250-A) Flat Tappet Camshaft, Cylinder Heads W/ Short TE Bump.

M35185F $2135

All - new to the forum. Just picked up a 1994 Sport Nautique Pro Boss 5.8L carb, with the Pro Tec ignition system. Long story short, the dealer I bought it from noticed water in the oil after they dewinterized it and decided to do a long block replacement at their expense.

I just received a copy of the invoice for the work to install the new crate motor. The crate motor item number is M35185F. Quick google search brings up a few different suppliers, they all use the same description.

Does anyone know if this motor shares the same specs (compression, cams, gt-40 heads) as the PCM Pro Boss? Want to make sure I understand what I’m getting here.

Thanks for your help!

[core-rider]

The block and rotating assembly should be the same basic parts... I'm not completely sure if the camshaft specs are the same... the heads should be the same GT-40 style heads your boat came with. The only thing I'm not completely sure of is if the original engine is reverse rotating or not. I don't think it is, but something to make sure of as it would require an different prop rotation to remedy.

I think you'll be okay with that replacement since I believe your engine isn't fuel injected so you shouldn't have any issues with a slightly different camshaft grind and engine displacement like the multi-port injection guys have had in the past.

[ddumbauld]

Thanks Core-rider.

i emailed the one of the vendors for this motor, Roadmaster Engine World. A person named Colleen Davis, I assume a customer service representative, responded saying the following:

“I just spoke with my builders and this M35185F engine has not been remanufactured with the GT40 heads, but the heads put on this engine have been modified to give the same HO and horse power of 285-310. I’m showing this 1994 351 flat tappet marine engine to have compression ratio of 10.5:1.”

Three questions:
1. That compression ratio (10.5:1) seems much higher than what’s shown, for example, in the 1995 PCM manual which shows CR of 8.3:1. does this seem odd to anyone?
2. What spark plugs and plug gap should I use?
3. Would a compression test of a few of the cylinders help me understand what I have?

Thanks!
Dave