Merc 2002 150XL (Carb) Saltwater not running right

[BigAhi]

OK, folks, here's the scoop:<br />Engine starts & idles fine; No problem getting RPMs in the 5*** range while in idle/neutral; put the boat in Fwd & can only get 3200RPMs on full throttle; changed fuel filter and added inline, transparent-casing fuel filter to watch for particulates; filter stays clean, same result ; changed spark plugs; same result ; engine is running ~175 degrees when warmed up and does get up to ~190-200 degrees when running @ 3200RPMs; telltale hole emits water in irregular fashion and water is very hot; my brother insists it's the water pump; how would that prevent boat from hitting WOT @5200RPM when in gear ? Any ideas would be appreciated before I start my wild goose chase!

 

[KCLOST]

Re: Merc 2002 150XL (Carb) Saltwater not running right

First off, DO NOT rev the engine above 2000 rpms while in neutral... You could severely damage the moving parts of the engine that way, when there is no load on it...<br /><br />Second, I would change the water pump/impeller to fix the temp issue... And then retest... There could be a rpm limiter on your engine to prevent futher temperature rise. But I'm not sure, you need to check your manual for that...

 

[BigAhi]

Re: Merc 2002 150XL (Carb) Saltwater not running right

Another theory: Prop is damaged ("stripped")and spins up to a certain resistance level and then can't keep up with the higher RPM. Is that possible? (I'd check it myself but I'm 75 miles from the boat right now).

 

[BigAhi]

Re: Merc 2002 150XL (Carb) Saltwater not running right

Sorry, you are correct, that wouldn't make sense. Thanks for the quick reply! So quick, I didn't answer the other questions: Boat is a 2002 21' Trophy W/A. First time this have ever happened. Boat has ~70 hours TOTAL on it. Used infrequently Prop is SS as supplied by the dealer when boat was purchased. Boat is ~ 3500lbs empty. Haven't done a compression check...hate to have to consider doing that on an engine with 70 hrs (and out of warranty)

 

[KCLOST]

Re: Merc 2002 150XL (Carb) Saltwater not running right

Your tachometer doesn't measure the rpm at the prop...<br /><br />So that theory isn't possible....<br /><br />Is this a recently purchased boat/motor? Is this a new problem or has this been the case since you've owned it? What prop (size and pitch) are you using? What type of boat is the motor on and what type of load is it carrying?<br />Have you checked compression on each cylinder?<br /><br />There are a lot of variables that can affect rpm, more info would be helpful.

 

[BigAhi]

Re: Merc 2002 150XL (Carb) Saltwater not running right

Answers to additional questions posted in same response above...Thanks