2001 350 MPI Merc Horizons

[Uniflite32]

I've got a 1975 Uniflite 32' Sport Sedan powered by 2001 350CI/300HP MerCruiser Horizon Inboards.<br />Serial #'s 0L671995, OL671999. Transmissions are Borg Warner 72C with V-drives. 1.51:1. I'm running 3 blade 13X17 cupped props. Enginges are rated 4400-4800 RPM. Top RPM with full fuel and water, RIB Dinghy on davits is 4700, a tick under 30 knots. 3200 RPM cruise is 18 knots. The engines run cool, < 160 degrees. The string of posts by Laura with the Sea Ray worry me. I've had zero problems with my motors and am showing about 450 hrs.<br />My question is this: I'm considering towing my 15' ski boat on some short trips. I'd like to do some of the towing at cruise RPM and some around 2000 RPM. Total boat weight will be approx. 800 LBS. Is there cause for worry? Am I going to suck valves? Should I decrease prop pitch? I'd like to hear from anyone that has experience doing this or from anyone who can give me advise on this subject. I don't want to ruin my motors.

 

[Doug Durako]

Re: 2001 350 MPI Merc Horizons

What type of harness are you using?<br /><br />I have pushed and pulled boats, docks, jet skis, etc., but never above idle speed.

 

[Uniflite32]

Re: 2001 350 MPI Merc Horizons

I do not have a harness yet as I haven't pulled the boat. The harness will be connected as a "Y" to my two stern cleats and be somewhere between 80 and 100 feet long so the boat sits just aft of where my wake comes together. Many cruisers in the Puget Sound area tow smaller boats from 13' Whalers up to small Grady Whites depending on what they are pulling them with. Most pull at cruise speed. Many are diesel boats although I do know of quite a few gas boats that regularly pull small boats behind. I don't think this will be an issue if I want to run slow. There are times I'd like to run up to cruise speed between 3100 and 3400 RPM but don't want to damage my engines. Previous posts indicate it would be better to prop my Uniflite to turn 5000-5200 RPM even though the engines are rated max at 4800 and I've had no problems. The Uniflite weighs 13500 LBS dry. This is more than the SeaRay in previous posts that had engine problems that seem to be related to overpropping even though it was propped to spec.

 

[Doug Durako]

Re: 2001 350 MPI Merc Horizons

I think that Sea Ray was running with Alpha drive legs, your V-drives and power packages should have no issues.<br /><br />Every "stock" Sea Ray boat I have ever tested was underpowered or overpropped---from the 18 foot ski model to the 38-foot cruiser I was on this April in Naples, Fla. <br /><br />You might check with the towing services in your harbor---most of them I have talked with in Florida use straight inboard setups and they tow stuff all day long, some for long distances. I am sure they have experimented with every prop setup imaginable.