Starboard engine losing power above about 4000 RPMs

rogerbum

I had a problem this past week with the starboard 135HP Honda engine on my Tomcat. In brief, it seems to run flawlessly until I get up to about 4000RPM (the exact RPM varies). Then it starts to fluctuate wildly in RPM and loses power. If I throttle back to a couple 1000 RPM and then go back up, it's fine until it hits 4000 at which point the problem re-appears. Any ideas on what might cause this? It seem more electrical/computer than mechanical to be but I suppose fuel starvation could also be an issue.

thataway · Posted: Mon Jul 06, 2015 7:22 pm Post subject:

My bet would be fuel. How are the filters, any water? Are you using E 10 or pure gas? Any water in the separator? How about in filters on the engine? Also could be fuel pump.

Bad time of year to be having those issues! Considering the fish you are catching!

rogerbum · Posted: Mon Jul 06, 2015 7:29 pm Post subject:

Pure gas. I need to check the filters. I have to admit that fuel starvation (which seems more obvious now) didn't occur to me at the time. I was having other issues at the time that were annoying me and my thinking wasn't that clear. I've got spare filters on board so I'll check that prior to pulling it.

TyBoo · Posted: Mon Jul 06, 2015 9:33 pm Post subject:

I haven't seen you talking as much about running and exercise lately. Have you put on weight? That can slow the starboard side down.

BrentB · Posted: Tue Jul 07, 2015 10:25 am Post subject:

It might be VST

rogerbum · Posted: Mon Jul 13, 2015 10:25 pm Post subject:

Turns out it was fuel starvation due to a badly clogged fuel filter on the fuel water separator. Since the engines had just been serviced and since I always ask for all the filters to be changed and for the shop to do what they would do if it was their own boat, I assumed that those filters had been changed. Also, I didn't realize that there is both a low pressure and a high pressure filter in the engine. Hence when I saw an invoice for two filters per side, I always thought one was in the engine and the other was the external fuel filter on the fuel water separator. Lesson learned - change the easy stuff yourself and print out an even more detailed list of what work you want done prior to taking it to the shop.

BrentB · Posted: Tue Jul 14, 2015 9:10 am Post subject:

I always wanted to install a gasoline rated vacuum gauge to OB side of a fuel filter