Engine/Manifold/Riser Temps? And maybe some other random questions....

Rusty Shackleford

New Member
Jul 3, 2017
6
Kaufman, Texas
Boat Info
1978 SRV 200 Sun Runner
Engines
305 Mercruiser
1978 SRV 200 Sun Runner w/305 SBC and Mercruiser Pre-alpha drive.

I picked this boat up cheap last year, and it is my first I/O boat (always ran OB's up til now). I have an above average mechanical ability, so I'm doing everything myself, but am researching decisions and procedures thoroughly.

Pulled the engine to swap out the collapsed rear mounts and deal with a wallowed out gimbal ring which caused loose steering. New raw water pump along with drive coupler, gimbal bearing/seal, trim/limit sensors, gimbal ring update to and alpha one with a square/splined pin, lower shift cable, and gobs of other stuff. This boat WAS a classic case of of the previous owner being a complete hack, so the deeper I got, the more problems I found. Until, of course, I had the motor (which seems to be in good condition) out and stripped down to a long block. Pretty much every moving part and gasket that did get unbolted is now new.

Got her all back together today and she fired right up on the first try (love the old school SBC's), warmed up, and idled just fine on the garden hose. Had one lifter on number 7 that took about a 2,500rpm rev to make it pump up, but once it did she purrs just fine. I just wanted to ask here and confirm the temps I'm seeing are acceptable?

I have a 160 degree stat in it. New temp gauge and sender shows 160. Port and Starboard manifolds and risers all running within about 2-5 degrees of one another, 154-158 degrees. Raw water hose showed 82-84 degrees downstream of the power steering heat exchanger.

Manifolds and riser both showing some corrosion inside, but not horrible. Hoping that replacement can wait til next year. Any concerns with the temps listed above?

Another question; I have SS plates between the manifolds and risers (rear riser, raw water cooled), and they have small holes where the water passages are, with a gasket on each side that has water passages as large as those of the manifolds and risers. As I understand it, there are different applications depending on whether it is a closed cooling system vs raw water. Which is right for a given application? Are mine the correct ones? Or should I pull them and let her flow? Here again, when I took them apart the small holes were either completely, or almost blocked by excess red RTV the P. O. had used when assembling them. I used a very thin coat when I put them together, with new gaskets, in an effort to avoid sealing the small holes up like they had been.

Also; I keep reading about some spring loaded balls on merc's somewhere around the t-stat housing, but mine doesn't have them, nor do I find them referenced in the SELOC book I have. As I understand it, these are used to balance the water flow to the manifolds/risers so they run even temps? Should I be concerned that mine doesn't have them?

Lastly- and completely off topic-Prop Selection; It has either a cleaver or chopper type prop on it, not really sure which one it is. I think I was told it was a 15 pitch, no markings on it anywhere, and the trailing edge of the blades are straight from the tip of the blade back to the hub. Haven't put a tape on it, but its diameter/shape meant the P.O. had to hack the steering tab off of the anode. The boat seemed to perform fine on the couple of quick shakedown trips I made last year (until I got the death rattle from the drive coupler due to the misalignment). It pulled up to 4,500rpm great, which I figure is about the max effective rpm for the engine anyway. It didn't seem to carry the bow as well as I thought it might, but admittedly, I didn't get crazy with the trim since the limiter had been eliminated from the wiring system and didn't want to destroy anything by trimming it too high. Just curious about the prop, because I have researched it, and can't pin down exactly what it is, or find any other comparable I/O's running one. Either way, I think the setup should be able to pull another inch or two of pitch, just not sure if I should try a different design? What that would be? And what pitch to start with for a tub like this one?

Oh, one more while we're here; It had a hydrofoil on the anti-cav plate. It was pretty old, the hardware wasn't SS and was rusted, so I removed and tossed it. Think I'll see major difference without it? I've found on my various OB boats that the hydrfoils are usually instaled to mask a bad setup, but with the IO's being a bit more limited when it comes to setup, I'm not sure if having one would be better or not. I know I won't truly know how it acts without it until I run it. Just curious about y'alls' thoughts on these things? I do plan on installing trim tabs at some point.

Anyway, thanks for reading. I look forward to the replies.

Keep the water on the outside.
 
If the propeller has a straight rear line from tip to hub it's a cleaver and the wrong application for your set up. Cleavers are for applications where the propeller surfaces while running. Think fast bass O/B's. They tend to lift the stern as well. Should be able to pull a 17 or 19 pitch standard prop pretty easy. Shouldn't need the hydrofoil with a proper set-up.
 

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