How high can I safely spin in neutral 81 Horizon

I want to isolate a noise &#40

I want to isolate a noise (motor or running gear or something else?)that occurs in the range of 2900-3400 rpm. Is it safe to spin it that high in neutral (i.e. in the slip). I can't believe I don't know the answer myself but here's a good place to ask! Thanks!!

Won't hurt a thing as long

Won't hurt a thing as long as long as the engine has cooling water flow and there's nothing else we should know about.

I read somewhere not to run th

I read somewhere not to run the engine RPMs while in neutral above 1500 while on a hose and muffs. Just back the boat on trailer into the water and put it into gear. I might be wrong but don't think I am other than maybe it was 2500 RPMs.

Thanks guys. It's a strai

Thanks guys. It's a straight inboard and would be sitting in the slip or better yet in open water. Just no load and no 'push' into the intake scoop.

"In the water it is fine. The

"In the water it is fine. The deal with using a garden hose and ear muffs much above 1000 or 1500 is that it doesn't supply enough water, and you can actually collapse the hose and cut off the water supply all together...not good "

"Too much time on my hands? I

"Too much time on my hands? I am considering a neighbour's winter-frozen 470 Mercruiser (3.7 litre, in-line 4, approx 165 hp) & swapping in a V6 or small V8. Questions... Does the bell housing over the 470 flywheel bolt up to other engines? Which ones? Is the 3.7 a GM engine? a Ford? Are the engine-mounted brackets (shifter, throttle) the same on all? I dunno where to find & price all the pieces I would need to accommodate the exhaust system... manifolds, risers, flap valves, rubber boots, screw clamps. How is the exhaust crossover arranged? Does it necessitate changing the outdrive casting that exhausts through the outdrive leg?
Guidance & prudent cautions will be gratefully received. TKU v much."